WO2026043473A1

WO2026043473A1 - Three-dimensional printing with flame-retardant compound

Info

Publication number: WO2026043473A1
Application number: PCT/US2024/043079
Authority: WO
Inventors: Emily LEVIN; Emre Hiro DISCEKICI; Jake H. Thomas
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2024-08-20
Filing date: 2024-08-20
Publication date: 2026-02-26
Anticipated expiration: 2027-02-20

Abstract

An example of a multi-fluid kit for three-dimensional printing includes a fusing agent, a detailing agent, and a flame-retardant cyclodextrin compound. The fusing agent includes an electromagnetic energy absorber and a first liquid vehicle. The detailing agent includes a second liquid vehicle. The flame-retardant cyclodextrin compound is included in the fusing agent, or in the detailing agent, or in both the fusing agent and the detailing agent.

Description

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THREE-DIMENSIONAL PRINTING WITH FLAME-RETARDANT COMPOUND

BACKGROUND

[0001 ] A three-dimensional (3D) printing process is a form of additive manufacturing that can be used to form 3D solid parts, e.g., using a digital model. 3D printing is often used in rapid product prototyping, mold generation, mold master generation, and short run manufacturing. Some additive 3D printing techniques involve the iterative application of successive layers of one or more materials, such as one or more build material composition(s), fusing agent(s), detailing agent(s), and the like. In some of these additive 3D printing techniques, at least partial curing, thermal merging/fusing, melting, sintering, etc. of the build material composition(s) may be used to form 3D solid parts, and the mechanism for material coalescence may depend upon the type of build material composition(s) used. For some materials, at least partial melting may be accomplished using heat-assisted extrusion, and for some other materials, curing or fusing may be accomplished using photonic energy sources, such as ultraviolet light, infrared light, or near-infrared light. 3D printing techniques may be used to generate 3D printed parts with various properties.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Features of examples of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though perhaps not identical, components. For the sake of brevity, reference numerals or features having a previously described function may or may not be described in connection with other drawings in which they appear. [0003] Fig. 1 is a schematic illustration of an example of a fluid set for three- dimensional printing that includes a fusing agent, a detailing agent, and a flameretardant cyclodextrin compound that is included in the fusing agent and/or in the detailing agent;

[0004] Fig. 2 is a schematic illustration of an example of a fluid set for three- dimensional printing that includes a fusing agent, a detailing agent, and a flameretardant agent; 86324975

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[0005] Fig. 3 is a flow diagram of an example of a method of three-dimensional printing;

[0006] Fig. 4 is a schematic view of an example of a method of three- dimensional printing that involves the use of a fusing agent, a detailing agent, and a flame-retardant cyclodextrin compound that is included in the fusing agent and/or in the detailing agent;

[0007] Fig. 5 is a schematic view of an example of a method of three- dimensional printing that involves the use of a fusing agent, a detailing agent, and a flame-retardant agent; and

[0008] Fig. 6 is a black-and-white reproduction of a photograph that was taken of two flame-retardant three-dimensional parts formed using an example of a method disclosed herein, after the flame-retardant parts had been exposed to flame/burning.

DETAILED DESCRIPTION

[0009] Some three-dimensional (3D) printing methods utilize an energy absorbing substance (e.g., an electromagnetic energy absorber) to pattern a layer of a build material composition, thereby forming a patterned region of the build material composition within the layer. In these methods, the layer of the build material composition is exposed to radiation, and the patterned region of the build material composition is coalesced/fused and becomes a layer of a 3D printed object. In the patterned region, the energy absorbing substance is capable of at least partially occupying voids between the particles of the build material composition and is also capable of spreading onto an exterior surface of particles within the build material composition. The energy absorbing substance is also capable of converting absorbed radiation energy into thermal energy, which may be used to coalesce/fuse build material particles that have been patterned with the energy absorbing substance. Fusing/coalescing causes the build material particles to join or blend to form a single entity (i.e. , the layer of the 3D printed object). Fusing/coalescing may involve at least partial thermal merging, melting, binding, and/or some other mechanism that causes the build material composition to form the layer of the 3D object. 86324975

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[0010] In some instances, it may be desirable to form 3D objects having specific properties (e.g., electrical properties, mechanical properties, chemical properties, etc.). For example, it may be desirable to form 3D objects having properties of flame- retardancy. Such 3D objects can prevent or slow the spreading of burning throughout an entirety of the 3D object when the object is exposed to flame or extreme heat. These properties of flame-retardancy are particularly useful in circumstances in which the 3D objects being formed will ultimately become exposed to flame or a high degree of heat.

[0011 ] Disclosed herein are three-dimensional printing fluids, materials, and methods that can be used to form flame-retardant 3D objects.

[0012] Throughout this disclosure, a weight percentage that is referred to as “wt% active” refers to the loading of an active component of a stock formulation that is present, e.g., in the fusing agent, or in the detailing agent, or in the flame-retardant agent, etc. For example, particles of an energy absorber may be present in a waterbased formulation (e.g., a stock solution or dispersion) before being incorporated into the fusing agent. In such examples, the wt% active of the energy absorber accounts for the loading (as a weight percent) of the energy absorber solids that are present in the formulation being described and does not account for the weight of the other components (e.g., water, etc.) that are present in the stock solution or dispersion with the energy absorber. The term “wt%,” without the term actives, refers to the loading (e.g., in the fusing agent) of a 100% active component that does not include other nonactive components therein.

[0013] Multi-fluid Kit 10

A first example of a multi-fluid kit for three-dimensional printing is shown in Fig. 1 . This example multi-fluid kit 10 includes: a fusing agent 12 including an electromagnetic energy absorber and a first liquid vehicle; a detailing agent 14 including a second liquid vehicle; and a flame-retardant cyclodextrin compound 15 that is included in the fusing agent 12, or in the detailing agent 14, or in both the fusing agent 12 and the detailing agent 14. Each of the components of the multi-fluid kit 10 will now be described. 86324975

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[001 ] Fusing Agent

[0015] The fusing agent 12 of the multi-fluid kit 10 generally includes an electromagnetic energy absorber (sometimes referred to herein as an “energy absorber” or “active material”) and a first liquid vehicle. In examples, the fusing agent 12 consists of the electromagnetic energy absorber and the first liquid vehicle. In other examples, the fusing agent 12 includes the electromagnetic energy absorber, the first liquid vehicle, and one or more additional components (e.g., additives), where the additional components may be incorporated into the first liquid vehicle during formation of the fusing agent 12. Each of the components of the fusing agent 12 will now be described.

[0016] Electromagnetic Energy Absorber(s)

[0017] The energy absorber of the fusing agent 12 is an electromagnetic radiation (EMR) absorbing material that converts absorbed EMR to thermal energy. [0018] The wavelengths of light that can be absorbed by the energy absorber will depend, in part, upon the type of electromagnetic energy absorber(s) that is/are included in the fusing agent 12.

[0019] Some examples of the fusing agent 12 include an energy absorber having substantial absorption (e.g., at least 80% absorption) at least in the visible light region (e.g., light wavelengths ranging from 400 nm to 780 nm). Fusing agents 12 that include these types of energy absorbers are referred to herein as a “core fusing agent 12.” Some examples of the core fusing agent 12 include an energy absorber that also has substantial absorption (e.g., at least 80% absorption) in the infrared region (e.g., 800 nm to 4000 nm), in addition to the near-infrared region. When exposed to electromagnetic radiation during 3D printing, the energy absorber in the core fusing agent 12 generates heat that is suitable for coalescing/fusing the build material composition in contact therewith, which leads to 3D objects (or 3D objects regions) having mechanical integrity and relatively uniform mechanical properties (e.g., strength, elongation at break, etc.).

[0020] As used herein and unless stated otherwise, the term “absorption” means that at least 80% of radiation having wavelengths within the specified range is absorbed by the material being described. Also used herein and unless stated 86324975

5 otherwise, “transparency” means that 25% or less of radiation having wavelengths within the specified range is absorbed by the material being described.

[0021 ] The energy absorber included in the core fusing agent 12 may be an infrared light absorbing colorant or a near-infrared light absorbing colorant. Any infrared or near-infrared colorants, e.g., those produced by Fabricolor Holdings LLC, Eastman Kodak, or BASF, Yamamoto, may be used in the core fusing agent. As one example, the core fusing agent may be a printing liquid formulation including carbon black as the energy absorber. Examples of this printing liquid formulation are commercially known as CM997A, 516458, C18928, C93848, C93808, or the like, all of which are available from HP Inc.

[0022] As another example, the core fusing agent 12 may be a printing liquid formulation including near-infrared absorbing dyes as the energy absorber. Examples of this printing liquid formulation are described in U.S. Patent No. 9,133,344, which is incorporated herein by reference in its entirety.

[0023] Some examples of the near-infrared absorbing dye are water-soluble nearinfrared absorbing dyes selected from the group consisting of:

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86324975 and a combination thereof. In the above formulations, M can be a divalent metal atom (e.g., copper, etc.) or can have OSChNa axial groups filling any unfilled valence shells if the metal is more than divalent (e.g., indium, etc.), R can be hydrogen or any Ci-Cs alkyl group (including substituted alkyl and unsubstituted alkyl), and Z can be a counterion such that the overall charge of the near-infrared absorbing dye is neutral. 86324975

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For example, the counterion can be a sodium ion (Na⁺), a lithium ion (Li⁺), a potassium ion (K⁺), ammonium (NH4⁺), etc.

[0024] Some other examples of the near-infrared absorbing dye that may be included in the core fusing agent are hydrophobic near-infrared absorbing dyes selected from the group consisting of: 86324975

86324975

12 and a combination thereof. For the hydrophobic near-infrared absorbing dyes, M can be a divalent metal atom (e.g., copper, etc.) or can include a metal that has Cl, Br, or OR’ (R’=H, CH₃, COCH3, COCH2COOCH3, COCH2COCH3) axial groups filling any unfilled valence shells if the metal is more than divalent, and R can be hydrogen or any Ci-Cs alkyl group (including substituted alkyl and unsubstituted alkyl).

[0025] Other near-infrared absorbing dyes or pigments may be used as the energy absorber in the core fusing agent 12. Some examples include anthraquinone dyes or pigments, metal dithiolene dyes or pigments, cyanine dyes or pigments, perylenediimide dyes or pigments, croconium dyes or pigments, pyrilium or 86324975

13 thiopyrilium dyes or pigments, boron-dipyrromethene dyes or pigments, or aza-boron- dipyrromethene dyes or pigments.

[0026] Anthraquinone dyes or pigments and metal (e.g., nickel) dithiolene dyes or pigments may have the following structures, respectively:

Anthraquinone dyes/pigments

Nickel dithiolene dyes/pigments 86324975

14 where R in the anthraquinone dyes or pigments may be hydrogen or any Ci-Cs alkyl group (including substituted alkyl and unsubstituted alkyl), and where R in the nickel dithiolene may be hydrogen, COOH, SO3, NH2, any Ci-Cs alkyl group (including substituted alkyl and unsubstituted alkyl), or the like.

[0027] Cyanine dyes or pigments and perylenediimide dyes or pigments may have the following structures, respectively:

Perylenediimide dyes/pigments where R in the perylenediimide dyes or pigments may be hydrogen or any Ci-Cs alkyl group (including substituted alkyl and unsubstituted alkyl). 86324975

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[0028] Croconium dyes or pigments and pyrilium or thiopyrilium dyes or pigments may have the following structures, respectively:

Pyrilium (X=O), thiopyrilium (X=S) dyes/pigments

[0029] Boron-dipyrromethene dyes or pigments and aza-boron-dipyrromethene dyes or pigments may have the following structures, respectively: 86324975

Boron-dipyrromethene dyes/pigments

Aza-boron-dipyrromethene dyes/pigments

[0030] Other suitable near-infrared absorbing dyes may include aminium dyes, tetraaryldiamine dyes, phthalocyanine dyes, and others.

[0031 ] Other near-infrared absorbing materials that may be used as the energy absorber in the core fusing agent 12 include conjugated polymers (i.e. , a polymer that has a backbone with alternating double and single bonds), such as poly(3,4- 86324975

17 ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), a polythiophene, poly(p-phenylene sulfide), a polyaniline, a poly(pyrrole), a poly(acetylene), poly(p- phenylene vinylene), polyparaphenylene, or combinations thereof.

[0032] The energy absorber of the core fusing agent 12 may, in some instances, be dispersed with a dispersant. When used, the dispersant uniformly distributes the energy absorber throughout the core fusing agent 12. Examples of suitable dispersants include polymer or small molecule dispersants, charged groups attached to the energy absorber surface, or other suitable dispersants. Some specific examples of suitable dispersants include a water-soluble acrylic acid polymer (e.g., CARBOSPERSE® K7028 available from Lubrizol), water-soluble styrene-acrylic acid copolymers/resins (e.g., JONCRYL® 296, JONCRYL® 671 , JONCRYL® 678, JONCRYL® 680, JONCRYL® 683, JONCRYL® 690, etc. available from BASF Corp.), a high molecular weight block copolymer with pigment affinic groups (e.g., DISPERBYK®-190 available BYK Additives and Instruments), or water-soluble styrene-maleic anhydride copolymers/resins.

[0033] Whether a single dispersant is used or a combination of dispersants is used in the core fusing agent, the total amount of dispersant(s) in the core fusing agent 12 may range from about 10 wt% active to about 200 wt% active based on a weight of the energy absorber in the core fusing agent 12.

[0034] Regardless of whether a dispersant is used, the total amount of the energy absorber/active material that is present in the core fusing agent 12 ranges from greater than 0 wt% active to about 40 wt% active, based on a total weight of the core fusing 12 agent. In other examples, the amount of the energy absorber/active material that is present in the core fusing agent 12 ranges from about 0.3 wt% active to about 30 wt% active, or from about 1 wt% active to about 20 wt% active, from about 1 .0 wt% active to about 10.0 wt% active, or from 4.0 wt% active to about 15.0 wt% active, based on the total weight of the core fusing agent. It is believed that these example energy absorber/active material loadings provide a balance between the core fusing agent 12 having jetting reliability (e.g., through an inkjet applicator) and heat and/or radiation absorbance efficiency. 86324975

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[0035] The energy absorber that is included in the core fusing agent 12 may have an average particle diameter (e.g., volume-weighted mean diameter) ranging from greater than 0 nm to less than 500 nm. In another example, the energy absorber in the core fusing agent 12 has an average particle diameter ranging from greater than 0 nm to 250 nm. In still another example, the energy absorber in the core fusing agent 12 has an average particle diameter ranging from about 10 nm to about 200 nm. [0036] Other examples of the fusing agent 12 include an energy absorber having absorption at wavelengths ranging from 800 nm to 4000 nm and having transparency at wavelengths ranging from 400 nm to 780 nm. This type of fusing agent 12 is referred to herein as a “primer fusing agent 12.” This combination of absorption (at wavelengths ranging from 800 nm to 4000 nm) and transparency (at wavelengths ranging from 400 nm to 780 nm) allows the primer fusing agent 12 to absorb enough radiation to coalesce/fuse build material particles in contact therewith, while allowing the 3D objects (or 3D objects regions) to be slightly colored or to retain a color used to form the 3D objects (e.g., white or off-white).

[0037] In some examples, the fusing agent 12 included in the multi-fluid kit 10 is the primer fusing agent 12, and the energy absorber included in the primer fusing agent 12 is a plasmonic resonance absorber having absorption at wavelengths ranging from 800 nm to 4000 nm and transparency at wavelengths ranging from 400 nm to 780 nm. As such, the absorption of this type of energy absorber is the result of plasmonic resonance effects. Electrons associated with the atoms of the energy absorber may be collectively excited by radiation, which results in collective oscillation of the electrons. The wavelengths that can excite and oscillate these electrons collectively are dependent on the number of electrons present in the energy absorber particles, which in turn is dependent on the size of the energy absorber particles. The amount of energy that can collectively oscillate the particle’s electrons is low enough that very small particles of the energy absorber (e.g., particles having a size ranging from 1 nm to 100 nm) may absorb radiation with wavelengths several times higher (e.g., from 8 to 800 or more times) the size of the particles of the energy absorber. The use of these particles allows the primer fusing agent 12 to be inkjet jettable as well as 86324975

19 electromagnetically selective (e.g., having absorption at wavelengths ranging from 800 nm to 4000 nm and transparency at wavelengths ranging from 400 nm to 780 nm). [0038] The energy absorber included in the primer fusing agent 12 may be an inorganic pigment. Examples of suitable inorganic pigments include lanthanum hexaboride (LaBe), tungsten bronzes (AxWC ), indium tin oxide (ln2O3:SnO2, ITO), antimony tin oxide (Sb2O3:SnO2, ATO), titanium nitride (TiN), cesium tungsten oxide (CS2WO4), aluminum zinc oxide (AZO), ruthenium oxide (RUO2), silver (Ag), gold (Au), platinum (Pt), iron pyroxenes (A_xFe_ySi2O6 wherein A is Ca or Mg, x = 1 .5-1 .9, and y = 0.1 -0.5), modified iron phosphates (AxFe_yPO4), modified copper phosphates (AxCu_yPOz), and modified copper pyrophosphates (AxCu_yP2O?). Tungsten bronzes may be alkali doped tungsten oxides. Examples of suitable alkali dopants (i.e., A in AxWOs) may be cesium, sodium, potassium, or rubidium. In an example, the alkali doped tungsten oxide may be doped in an amount ranging from greater than 0 mol% to about 0.33 mol% based on the total mol% of the alkali doped tungsten oxide.

Suitable modified iron phosphates (AxFe_yPO) may include copper iron phosphate (A = Cu, x = 0.1-0.5, and y = 0.5-0.9), magnesium iron phosphate (A = Mg, x = 0.1 -0.5, and y = 0.5-0.9), and zinc iron phosphate (A = Zn, x = 0.1 -0.5, and y = 0.5-0.9). For the modified iron phosphates, it is to be understood that the number of phosphates may change based on the charge balance with the cations. Suitable modified copper pyrophosphates (AxCu_yP2O?) include iron copper pyrophosphate (A = Fe, x = 0-2, and y = 0-2), magnesium copper pyrophosphate (A = Mg, x = 0-2, and y = 0-2), and zinc copper pyrophosphate (A = Zn, x = 0-2, and y = 0-2). Combinations of the inorganic pigments may also be used.

[0039] The energy absorber of the primer fusing agent 12 may, in some instances, be dispersed with a dispersant. As such, the dispersant helps to uniformly distribute the energy absorber throughout the primer fusing agent. Examples of suitable dispersants include polymer or small molecule dispersants, charged groups attached to the energy absorber surface, or other suitable dispersants. Some specific examples of suitable dispersants include a water-soluble acrylic acid polymer (e.g., CARBOSPERSE® K7028 available from Lubrizol), water-soluble styrene-acrylic acid copolymers/resins (e.g., JONCRYL® 296, JONCRYL® 671 , JONCRYL® 678, 86324975

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JONCRYL® 680, JONCRYL® 683, JONCRYL® 690, etc. available from BASF Corp.), a high molecular weight block copolymer with pigment affinic groups (e.g., DISPERBYK®-190 available BYK Additives and Instruments), or water-soluble styrene-maleic anhydride copolymers/resins.

[0040] Whether a single dispersant is used or a combination of dispersants is used in the primer fusing agent 12, the total amount of dispersant(s) in the primer fusing agent 12 may range from about 10 wt% active to about 200 wt% active based on a weight of the energy absorber in the primer fusing agent 12.

[0041 ] Regardless of whether a dispersant is used, the amount of the energy absorber that is present in the primer fusing agent 12 ranges from greater than 0 wt% active to about 40 wt% active, based on a total weight of the primer fusing agent 12. In other examples, the amount of the energy absorber that is present in the primer fusing agent 12 ranges from about 0.3 wt% active to 30 wt% active, or from about 1 wt% active to about 20 wt% active, from about 1 .0 wt% active to about 10.0 wt% active, or from about 4.0 wt% active to about 15.0 wt% active, based on the total weight of the primer fusing agent 12. It is believed that these example energy absorber loadings provide a balance between the primer fusing agent 12 having jetting reliability (e.g., through an inkjet applicator) and heat and/or radiation absorbance efficiency.

[0042] The energy absorber that is included in the primer fusing agent 12 may have an average particle diameter (e.g., volume-weighted mean diameter) ranging from greater than 0 nm to less than 220 nm. In another example, the energy absorber in the primer fusing agent has an average particle diameter ranging from greater than 0 nm to 120 nm.

[0043] A silane coupling agent may also be added to the primer fusing agent 12 to help bond the organic (e.g., dispersant) and inorganic (e.g., pigment) materials. Examples of suitable silane coupling agents include the SILQUEST® A series manufactured by Momentive.

[0044] Whether a single silane coupling agent is used or a combination of silane coupling agents is used, the total amount of silane coupling agent(s) in the primer fusing agent 12 may range from about 0.1 wt% active to about 50 wt% active, based 86324975

21 on the weight of the energy absorber in the primer fusing agent 12. In an example, the total amount of silane coupling agent(s) in the primer fusing agent 12 ranges from about 1 wt% to about 30 wt% based on the weight of the energy absorber in the primer fusing agent 12. In another example, the total amount of silane coupling agent(s) in the primer fusing agent 12 ranges from about 2.5 wt% active to about 25 wt% active, based on the weight of the energy absorber in the primer fusing agent 12.

[0045] Still other examples of the energy absorber that may be used in either the core fusing agent 12 or in the primer fusing agent 12 absorb at least some of the light wavelengths within the range of 400 nm to 4000 nm. Examples of this type of energy absorber include glass fibers, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, phosphate pigments, silicate pigments, and/or natural filler materials, such as nano-cellulose. These energy absorbers are often white or lightly colored.

Phosphates may have a variety of counterions, such as copper, zinc, iron, magnesium, calcium, strontium, the like, and combinations thereof. Examples of phosphates can include M2P2O7, M4P2O9, M5P2O10, M3(PO4)2, M(POs)2, M2P4O12, and combinations thereof, where M represents a counterion having an oxidation state of +2, such as those listed above or a combination thereof. For example, M2P2O?can include compounds such as CU2P2O7, Cu/MgP2O7, Cu/ZnP2O7, or any other suitable combination of counterions. Silicates can have the same or similar counterions as phosphates. Example silicates can include M2SiO4, M2Si20e, and other silicates where M is a counterion having an oxidation state of +2. For example, the silicate M2Si20e can include Mg2Si20e, Mg/CaSi2Oe, MgCuSi2Oe, Cu2Si20e, Cu/ZnSi2Oe, or other suitable combination of counterions. It is noted that the phosphates and silicates described herein are not limited to counterions having a +2 oxidation state, and that other counterions can also be used to prepare other suitable near-infrared pigments. [0046] In addition to the energy absorber, the fusing agent 12 in the multi-fluid kit 10 also includes the (first) liquid vehicle, which will now be described.

[0047] Fusing Agent Liquid Vehicle

[0048] Any example of the fusing agent 12 (i.e., the core fusing agent 12 or the primer fusing agent 12) includes a (first) liquid vehicle. The fusing agent vehicle, or “FA vehicle,” may refer to the liquid in which the energy absorber(s) is/are dispersed or 86324975

22 dissolved to form the fusing agent 12. A wide variety of FA vehicles, including aqueous and non-aqueous solvents and co-solvents, may be used in the fusing agent vehicles. In some examples, the FA vehicle may consist of water alone, an aqueous solvent alone, or a non-aqueous solvent alone and no other components. In other examples, the FA vehicle may further include additional components, depending, in part, upon the applicator that is to be used to dispense the fusing agent 12. As examples, the fusing agent 12 may further include: co-solvent(s), surfactant(s), antimicrobial agent(s), anti-kogation agent(s), chelating agent(s), humectant(s), and/or flame-retardant cyclodextrin compound(s) 15, any of which may be added to the liquid vehicle of the fusing agent 12.

[0049] The FA vehicle may include a water soluble or water miscible organic solvent and/or co-solvent. Classes of water soluble or water miscible organic cosolvents that may be used include aliphatic alcohols, aromatic alcohols, diols, glycol ethers, polyglycol ethers, lactams, formamides (substituted and unsubstituted), acetamides (substituted and unsubstituted), glycols, and long chain alcohols. Examples of these co-solvents include primary aliphatic alcohols, secondary aliphatic alcohols, 1 ,2-alcohols, 1 ,3-alcohols, 1 ,5-alcohols, 1 ,6-hexanediol or other diols (e.g., 1 ,2-propanediol, 1 ,5-pentanediol, 2-methyl-1 ,3-propanediol, etc.), ethylene glycol alkyl ethers, propylene glycol, propylene glycol alkyl ethers, higher homologs (C6-C12) of polyethylene glycol alkyl ethers, triethylene glycol, tetraethylene glycol, tripropylene glycol methyl ether, N-alkyl caprolactams, unsubstituted caprolactams, 2-pyrrolidone, 1-methyl-2-pyrrolidone, 1 -(2-hydroxyethyl)-2-pyrrolidone, and the like. Other examples of organic co-solvents include dimethyl sulfoxide (DMSO), isopropyl alcohol, ethanol, pentanol, acetone, or the like.

[0050] The co-solvent(s) may be present in the fusing agent 12 in a total amount ranging from greater than 0.01 wt% to about 20 wt%, based on the total weight of the fusing agent 12. In an example, the fusing agent 12 includes from about 2 wt% to about 15 wt%, or from about 7.5 wt% to about 12.5 wt% of the co-solvent(s), based on the total weight of the fusing agent 12. In a specific example, the co-solvent(s) is/are present in the fusing agent 12 in an amount of about 10.0 wt%, based on the total weight of the fusing agent 12. 86324975

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[0051 ] The fusing agent vehicle may further include a surfactant. Suitable surfactant(s) for the fusing agent 12 include non-ionic, anionic, or cationic surfactants. Some example surfactants include alkyl polyethylene oxides, alkyl phenyl polyethylene oxides, polyethylene oxide block copolymers, acetylenic polyethylene oxides, polyethylene oxide (di)esters, polyethylene oxide amines, protonated polyethylene oxide amines, protonated polyethylene oxide amides, dimethicone copolyols, substituted amine oxides, fluorosurfactants, and the like. Some specific examples include a self-emulsifiable, non-ionic wetting agent based on acetylenic diol chemistry (e.g., SURFYNOL® SEF from Evonik Degussa), a non-ionic fluorosurfactant (e.g., CAPSTONE® fluorosurfactants, such as CAPSTONE® FS-35, from Chemours), an ethoxylated low-foam wetting agent (e.g., SURFYNOL® 440 or SURFYNOL® CT-111 from Evonik Degussa), an ethoxylated wetting agent and molecular defoamer (e.g., SURFYNOL® 420 from Evonik Degussa), non-ionic wetting agents and molecular defoamers (e.g., SURFYNOL® 104E from Evonik Degussa), and/or water-soluble, non-ionic surfactants (e.g., TERGITOL™ TMN-6, TERGITOL™ 15-S-7, or TERGITOL™ 15-S-9 (a secondary alcohol ethoxylate) from The Dow Chemical Company or TEGO® Wet 510 (organic surfactant) available from Evonik Degussa). Yet another suitable (anionic) surfactant includes alkyldiphenyloxide disulfonate (e.g., the DOWFAX™ series, such a 2A1 , 3B2, 8390, C6L, C10L, and 30599, from The Dow Chemical Company).

[0052] Whether a single surfactant is used or a combination of surfactants is used, the total amount of surfactant(s) in the fusing agent 12 may range from about 0.01 wt% active to about 3 wt% active, based on the total weight of the fusing agent 12. In an example, the total amount of surfactant(s) in the fusing agent 12 is about 0.75 wt% active, based on the total weight of the fusing agent 12.

[0053] The fusing agent vehicle may further include an antimicrobial agent. Antimicrobial agents are also known as biocides and/or fungicides. Examples of suitable antimicrobial agents include the NUOSEPT® (Ashland Inc.), UCARCIDE™ or KORDEK™ or ROCIMA™ (The Dow Chemical Company), PROXEL® (Arch Chemicals) series, ACTICIDE® B20 and ACTICIDE® M20 and ACTICIDE® MBL (blends of 2-methyl-4-isothiazolin-3-one (MIT), 1 ,2-benzisothiazolin-3-one (BIT) and 86324975

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Bronopol) (Thor Chemicals), AXIDE™ (Planet Chemical), NIPACIDE™ (Clariant), blends of 5-chloro-2-methyl-4-isothiazolin-3-one (CIT or CMIT) and MIT under the tradename KATHON™ (The Dow Chemical Company), and combinations thereof. [0054] In an example, the total amount of antimicrobial agent(s) in the fusing agent 12 ranges from about 0.01 wt% active to about 0.05 wt% active, based on the total weight of the fusing agent 12.

[0055] The fusing agent vehicle may further include an anti-kogation agent that is to be jetted using thermal inkjet printing. “Kogation” refers to the deposit of dried printing liquid (e.g., fusing agent) on a heating element of a thermal inkjet printhead. Anti- kogation agent(s) is/are included to assist in preventing the buildup of kogation.

[0056] Examples of suitable anti-kogation agents include oleth-3-phosphate (commercially available as CRODAFOS™ O3A or CRODAFOS™ N-3A) or dextran 500k. Other suitable examples of the anti-kogation agents include CRODAFOS™ HCE (phosphate-ester from Croda Int.), CRODAFOS® 010A (oleth-10-phosphate from Croda Int.), or DISPERSOGEN® LFH (polymeric dispersing agent with aromatic anchoring groups, acid form, anionic, from Clariant), etc. It is to be understood that any combination of the anti-kogation agents listed may be included in the fusing agent 12.

[0057] The anti-kogation agent may be present in the fusing agent 12 in an amount ranging from about 0.01 wt% active to about 1 .5 wt% active, based on the total weight of the fusing agent 12.

[0058] The fusing agent vehicle may further include chelating agents, e.g., to eliminate the deleterious effects of heavy metal impurities. In an example, the chelating agent is selected from the group consisting of methylglycinediacetic acid, trisodium salt; 4,5-dihydroxy-1 ,3-benzenedisulfonic acid disodium salt monohydrate; ethylenediaminetetraacetic acid (EDTA); hexamethylenediamine tetra(methylene phosphonic acid), potassium salt; and a combination thereof. Methylglycinediacetic acid, trisodium salt (Na3MGDA) is commercially available as TRILON® M from BASF Corp. 4,5-dihydroxy-1 ,3-benzenedisulfonic acid disodium salt monohydrate is commercially available as TIRON™ monohydrate. Hexamethylenediamine 86324975

25 tetra(methylene phosphonic acid), potassium salt is commercially available as DEQUEST® 2054 from Italmatch Chemicals.

[0059] Whether a single chelating agent is used in the fusing agent 12 or a combination of chelating agents is used in the fusing agent 12, the total amount of chelating agent(s) in the fusing agent 12 may range from 0 wt% active to about 0.5 wt% active based on the total weight of the fusing agent 12. In an example, the chelating agent is present in the fusing agent 12 in an amount ranging from about 0.01 wt% active to about 0.2 wt% active, based on the total weight of fusing agent 12.

[0060] The fusing agent vehicle may further include humectant(s). An example of a suitable humectant is ethoxylated glycerin having the following formula: in which the total of a+b+c ranges from about 5 to about 60, or in other examples, from about 20 to about 30. An example of the ethoxylated glycerin is LIPONIC® EG-1 (LEG-1 , glycereth-26, a+b+c=26, available from Lipo Chemicals).

[0061 ] In an example, the total amount of the humectant(s) present in the fusing agent 12 ranges from 0.01 wt% active to about 10 wt% active, based on the total weight of the fusing agent 12.

[0062] It is to be understood that the first liquid vehicle of the fusing agent 12 may also include the flame-retardant cyclodextrin compound 15, as will be described hereinbelow.

[0063] When any of these additional components/additives are present in the fusing agent vehicle, the balance of the fusing agent vehicle is water (e.g., deionized water, 86324975

26 purified water, etc.), which as described herein, may vary depending upon the other components in the fusing agent 12.

[0064] Detailing Agent

[0065] The multi-fluid kit 10 shown in Fig. 1 also includes the detailing agent 14.

The detailing agent 14 includes the second liquid vehicle (e.g., “detailing agent vehicle”), which may be water (e.g., deionized water, distilled water, etc.), an aqueous solvent, or a non-aqueous solvent. In an example, the detailing agent 14 consists of water.

[0066] In some examples, the detailing agent 14 vehicle further includes a surfactant and a co-solvent. The detailing agent 14 may consist of the water, the surfactant, and the co-solvent, with no other components being present in the detailing agent 14.

[0067] The surfactant(s) that may be used in the detailing agent 14 vehicle include any of the surfactants listed herein in reference to the fusing agent 12, or any other suitable surfactant. The total amount of surfactant(s) in the detailing agent 14 may range from about 0.01 wt% active to about 5 wt% active, based on a total weight of the detailing agent 14.

[0068] The co-solvent(s) that may be used in the detailing agent 14 vehicle include any of the co-solvents listed herein in reference to the fusing agent 12, or any other suitable co-solvent. The total amount of co-solvent(s) in the detailing agent 14 may range from about 0.01 wt% to about 65 wt%, based on the total weight of the detailing agent 14.

[0069] In some examples, the detailing agent 14 vehicle does not include a colorant. In these examples, the detailing agent 14 may be colorless. As used herein, “colorless,” means that the detailing agent 14 is achromatic and does not include a colorant.

[0070] In some other examples, the detailing agent 14 vehicle does include a colorant. The detailing agent 14 may consist of the colorant, the surfactant, the cosolvent, and a balance of water, with no other components.

[0071 ] When the detailing agent 14 vehicle includes the colorant, the colorant may be a dye of any color having substantially no absorbance in a range of 650 nm to 2500 86324975

27 nm. By “substantially no absorbance,” it is meant that the dye absorbs no radiation having wavelengths in a range of 650 nm to 2500 nm, or that the dye absorbs less than 10% of radiation having wavelengths in a range of 650 nm to 2500 nm. The dye may also be capable of absorbing radiation with wavelengths of 650 nm or less. As such, the dye absorbs at least some wavelengths within the visible spectrum, but absorbs little or no wavelengths within the near-infrared spectrum. This is in contrast to the active material (i.e. , electromagnetic energy absorber) in the fusing agent 12, which absorbs wavelengths within the near-infrared spectrum in at least some examples. As such, the colorant in the detailing agent 14 will not substantially absorb the fusing radiation, and thus will not initiate melting and fusing (coalescence) of the build material composition in contact therewith when the build material layer is exposed to the energy during 3D object fabrication.

[0072] It may be desirable to add color to the detailing agent 14 when the detailing agent 14 is applied to the edge of a colored part. Color in the detailing agent 14 may be desirable when used at a part edge because some of the colorant may become embedded in the polymeric build material that fuses/coalesces at the edge. As such, in some examples, the dye in the detailing agent 14 may be selected so that its color matches the color of the active material in the fusing agent 12. As examples, the dye may be any azo dye having sodium or potassium counter ion(s) or any diazo (i.e., double azo) dye having sodium or potassium counter ion(s), where the color of azo or dye azo dye matches the color of the fusing agent 12.

[0073] In an example, the dye is a black dye. Some examples of the black dye include azo dyes having sodium or potassium counter ion(s) and diazo (i.e., double azo) dyes having sodium or potassium counter ion(s). Examples of azo and diazo dyes may include tetrasodium (6Z)-4-acetamido-5-oxo-6-[[7-sulfonato-4-(4- sulfonatophenyl)azo-1 -naphthyl]hydrazono]naphthalene-1 ,7-disulfonate with a 86324975

28

(commercially available as Food Black 1 ); tetrasodium 6-amino-4-hydroxy-3-[[7- sulfonato-4-[(4-sulfonatophenyl)azo]-1 -naphthyl]azo]naphthalene-2,7-disulfonate with a chemical structure of:

(commercially available as Food Black 2); tetrasodium (6E)-4-amino-5-oxo-3-[[4-(2- sulfonatooxyethylsulfonyl)phenyl]diazenyl]-6-[[4-(2- sulfonatooxyethylsulfonyl)phenyl]hydrazinylidene]naphthalene-2,7-disulfonate with a chemical structure of:

86324975

29

(commercially available as Reactive Black 31 ); tetrasodium (6E)-4-amino-5-oxo-3-[[4-(2- sulfonatooxyethylsulfonyl)phenyl]diazenyl]-6-[[4-(2- sulfonatooxyethylsulfonyl)phenyl]hydrazinylidene]naphthalene-2,7-disulfonate with a and combinations thereof. Some other commercially available examples of the dye used in the detailing agent 14 include multipurpose black azo-dye based liquids, such as PRO-JET® Fast Black 1 (made available by Fujifilm Holdings), and black azo-dye based liquids with enhanced water fastness, such as PRO-JET® Fast Black 2 (made available by Fujifilm Holdings).

[0074] In some instances, in addition to the black dye, the colorant in the detailing agent 14 may further include another dye. In an example, the other dye may be a cyan dye that is used in combination with any of the dyes disclosed herein. The other dye may also have substantially no absorbance above 650 nm. The other dye may be any colored dye that contributes to improving the hue and color uniformity of the final 3D part. 86324975

30

[0075] Some examples of the other dye include a salt, such as a sodium salt, an ammonium salt, or a potassium salt. Some specific examples include ethy l-[4-[[4- [ethyl-[(3-sulfophenyl) methyl] amino] phenyl]-(2-sulfophenyl) ethylidene]-1 -cyclohexa- 2,5-dienylidene]-[(3-sulfophenyl) methyl] azanium with a chemical structure of:

(commercially available as Acid Blue 9, where the counter ion may alternatively be sodium counter ions or potassium counter ions); sodium 4-[(E)-{4- [benzyl(ethyl)amino]phenyl}{(4E)-4-[benzyl(ethyl)iminio]cyclohexa-2,5-dien-1- ylidene}methyl]benzene-1 ,3-disulfonate with a chemical structure of: as Acid Blue 7); and a phthalocyanine with a chemical structure of: 86324975

31 (commercially available as

Direct Blue 199); and combinations thereof.

[0076] In an example of the detailing agent 14, the dye may be present in an amount ranging from about 1 wt% active to about 3 wt% active, based on the total weight of the detailing agent 14. In another example of the detailing agent 14 including a combination of dyes, one dye (e.g., the black dye) is present in an amount ranging from about 1.50 wt% active to about 1 .75 wt% active based on the total weight of the detailing agent, and the other dye (e.g., the cyan dye) is present in an amount ranging from about 0.25 wt% active to about 0.50 wt% active, based on the total weight of the detailing agent 14.

[0077] Regardless of whether a colorant is included in the detailing agent 14, the detailing agent 14 vehicle may further include additional components, such as anti- kogation agent(s), antimicrobial agent(s), chelating agent(s), humectant(s), and/or flame-retardant cyclodextrin compound(s) 15.

[0078] The anti-kogation agent(s) that may be used in the detailing agent 14 include any of the anti-kogation agents listed herein in reference to the fusing agent 12, or any other suitable anti-kogation agent. The total amount of anti-kogation agent(s) in the detailing agent 14 may range from about 0.01 wt% active to about 1.5 wt% active, based on the total weight of the detailing agent 14.

[0079] The antimicrobial agent(s) that may be used in the detailing agent 14 include any of the antimicrobial agents listed herein in reference to the fusing agent 12, or any 86324975

32 other suitable antimicrobial agent. The total amount of antimicrobial agent(s) in the detailing agent 14 may range from about 0.01 wt% active to about 0.05 wt% active, based on the total weight of the detailing agent 14.

[0080] The chelating agent(s) that may be used in the detailing agent 14 include any of the chelating agents listed herein in reference to the fusing agent 12, or any other suitable chelating agent. The total amount of chelating agent(s) in the detailing agent 14 may range from about 0.01 wt% active to about 0.2 wt% active, based on the total weight of the detailing agent 14.

[0081 ] The humectant(s) that may be used in the detailing agent 14 include any of the humectant(s) listed herein in reference to the fusing agent 12, or any other suitable humectant. The total amount of humectant(s) in the detailing agent 14 may range from about 0.01 wt% active to about 10 wt% humectant, based on the total weight of the detailing agent 14.

[0082] The detailing agent vehicle may further include a flame-retardant cyclodextrin compound 15, as will be described herein below.

[0083] The balance of the detailing agent 14 is water (e.g., when other components besides water are included in the detailing agent 14). As such, the amount of water present in the detailing agent 14 may vary depending upon the amounts of the other components that are included.

[0084] As such, the second liquid vehicle of the detailing agent 14 may include an aqueous or non-aqueous solvent, a co-solvent, a surfactant, an anti-kogation agent, a chelating agent, an antimicrobial agent, a humectant, and a flame-retardant cyclodextrin compound 15.

[0085] Flame-retardant Cvclodextrin Compound

[0086] The multi-fluid kit 10 shown in Fig. 1 also includes (a) flame-retardant cyclodextrin compound(s) 15, which is/are included in the fusing agent 12 and/or in the detailing agent 14. As described, the flame-retardant cyclodextrin compound 15 may be incorporated into the (first) liquid vehicle of the fusing agent 12, and/or the flameretardant cyclodextrin compound 15 may be incorporated into the (second) liquid vehicle of the detailing agent 14 during formation of the respective agents 12, 14. 86324975

33

[0087] Fused/coalesced polymeric material (e.g., at an outer surface of a three- dimensional part) that is in contact with or that is in proximity to the flame-retardant cyclodextrin compound 15 resists/slows burning and thus exhibits properties of “flame- retardancy.” In other words, the polymeric material at the outer surface of the 3D part may become charred when exposed to heat from a flame, due in part to the presence of the flame-retardant cyclodextrin compound 15. This charring forms a carbon layer at the outer surface of the polymeric material of the three-dimensional object and slows or prevents burning/spreading of flame throughout an entirety of the three- dimensional object. Further, because the flame-retardant cyclodextrin compound 15 is included in the fusing agent 12 or in the detailing agent 14 of the multi-fluid kit 10, each of which is selectively jettable, the flame-retardant cyclodextrin compound 15 can be selectively incorporated into a three-dimensional object layer at suitbable regions during formation of the layer (as will be described in reference to Figure 4 herein). [0088] The flame-retardant cyclodextrin compound 15 may be in the form of a crystalline solid (e.g., prior to its incorporation into the first or second liquid vehicle of the fusing agent 12 or the detailing agent 14, respectively). In an example, the flameretardant cyclodextrin compound 15 is selected from the group consisting of a- cyclodextrin, [3-cyclodextrin, y-cyclodextrin, hydroxypropyl-[3-cyclodextrin, hydroxyethyl-a-cyclodextrin, carboxymethyl-a-cyclodextrin, carboxy-methyl-[3- cyclodextrin, and a combination thereof. In a specific example, the flame-retardant cyclodextrin compound 15 in the fusing agent 12 or in the detailing agent 14 of the multi-fluid kit 10 is the hydroxypropyl-[3-cyclodextrin. These agents 12, 14 may be particularly suitable for thermal inkjet printing applications.

[0089] As described, the flame-retardant cyclodextrin compound 15 may be present in (the liquid vehicle of) the fusing agent 12 or in the detailing agent 14. In an example, the flame-retardant cyclodextrin compound 15 is included in the fusing agent 12 and is absent from the detailing agent 14. In this example, regions of the build material composition patterned with the fusing agent 12 will exhibit properties of flame- retardancy (e.g., after fusing/coalescing the build material composition).

[0090] As such, an example of the fusing agent 12 includes the electromagnetic energy absorber, the liquid vehicle, and the flame-retardant cyclodextrin compound 15. 86324975

34

In a specific example, the fusing agent 12 consists of the energy absorber, the (first) liquid vehicle, the flame-retardant cyclodextrin compound 15, and no other components. In other examples, the fusing agent 12 includes the energy absorber, the (first) liquid vehicle, the flame-retardant cyclodextrin compound 15, and any of the additives described herein (e.g., co-solvent(s), surfactant(s), anti-kogation agent(s), antimicrobial agent(s) chelating agent(s), and/or humectant(s)).

[0091 ] In another example, the flame-retardant cyclodextrin compound 15 is included in the detailing agent 14 and is absent from the fusing agent 12. In this example, regions of the build material composition patterned with the detailing agent 14 will exhibit properties of flame-retardancy (e.g., after fusing/coalescing the build material).

[0092] In a specific example, the detailing agent 14 consists of the second liquid vehicle, the flame-retardant cyclodextrin compound 15, and no other components. In other examples, the detailing agent 14 includes or consists of the (second) liquid vehicle, the flame-retardant cyclodextrin compound 15, and any of the additives described herein (e.g., co-solvent(s), surfactant(s), anti-kogation agent(s), antimicrobial agent(s), chelating agent(s), and/or humectant(s)).

[0093] In still another example, the flame-retardant cyclodextrin compound 15 is included in both the fusing agent 12 and the detailing agent 14. In this example, areas of the build material composition patterned with the fusing agent 12 or patterned with the detailing agent 14 will exhibit properties of flame-retardancy (e.g., before and/or after fusing/coalescing the build material).

[0094] In any example, the flame-retardant cyclodextrin compound 15 may be present in the fusing agent 12 or in the detailing agent 14 in an amount ranging from about 0.1 wt% to about 30 wt%, based on the total weight of the fusing agent 12 or of the detailing agent 14, respectively. In an example, the flame-retardant cyclodextrin compound 15 is present in the fusing agent 12 or in the detailing agent 14 in an amount ranging from about 15 wt% to about 25 wt%, based on the total weight of the fusing agent 12 or of the detailing agent 14, respectively. In one specific example, the flame-retardant cyclodextrin compound 15 is present in the fusing agent 12 in an amount of about 20.0 wt%, based on the total weight of the fusing agent 12. In this 86324975

35 example, the flame-retardant cyclodextrin compound 15 may be absent from the detailing agent 14. In another specific example, the flame-retardant cyclodextrin compound 15 is present in the detailing agent 14 in an amount of about 20.0 wt%, based on the total weight of the detailing agent 14. In this example, the flameretardant cyclodextrin compound 15 may be absent from the fusing agent 12.

[0095] Multi-fluid Kit 2

[0096] A second example of the multi-fluid kit for three-dimensional printing is shown in Fig. 2. This example multi-fluid kit 20 includes a fusing agent 12’ including an electromagnetic energy absorber and a first liquid vehicle; a detailing agent 14’ including a second liquid vehicle; and a flame-retardant agent 16 including a cyclodextrin compound and a third liquid vehicle. Each of the components of the multifluid kit 20 will now be described.

[0097] Fusing Agent 12’

[0098] The multi-fluid kit 20 includes the fusing agent 12’. The fusing agent 12’ that is included in the multi-fluid kit 20 may include any of the components (e.g., energy absorbers and/or liquid vehicle component(s)) of the fusing agent 12 that is included in the multi-fluid kit 10, and in the same respective amounts.

[0099] It is to be understood, however, that unlike some examples of the fusing agent 12 of the multi-fluid kit 10, the fusing agent 12’ that is included in the multi-fluid kit 20 does not include the flame-retardant cyclodextrin compound 15. This is because in the multi-fluid kit 20, the flame-retardant cyclodextrin compound 15 is included in the separate flame-retardant agent 16 (as will be described in more detail herein).

[0100] The energy absorbers of either the primer fusing agents or core fusing agents described herein in reference to the fusing agent 12 may also be used in the fusing agent 12’. As such, the fusing agent 12’ in the multi-fluid kit 20 generally includes an electromagnetic energy absorber (i.e., active material) and a first liquid vehicle.

[0101 ] In an example, the fusing agent 12’ of the multi-fluid kit 20 consists of the electromagnetic energy absorber and the first liquid vehicle. 86324975

36

[0102] In another example, the fusing agent 12’ includes the electromagnetic energy absorber, the first liquid vehicle, and one or more additional components (e.g., additives), such as any co-solvent(s), surfactant(s), anti-kogation agent(s), antimicrobial agent(s), chelating agent(s), or humectant(s) described herein in reference to the fusing agent 12 of the multi-fluid kit 10, and in the same respective amounts.

[0103] Detailing Agent 14’

[0104] The multi-fluid kit 20 further includes the detailing agent 14’. The detailing agent 14’ that is included in the multi-fluid kit 20 may include any of the components of the detailing agent 14 described herein in reference to the multi-fluid kit 10, and in the same respective amounts. As such, the detailing agent 14’ in the multi-fluid kit 20 generally includes a second liquid vehicle.

[0105] It is to be understood, however, that unlike some examples of the detailing agent 14 of the multi-fluid kit 10, the detailing agent 14’ that is included in the multifluid kit 20 does not include the flame-retardant cyclodextrin compound 15. This is because in the multi-fluid kit 20, the flame-retardant cyclodextrin compound 15 is included in the separate flame-retardant agent 16.

[0106] The second liquid vehicle of the detailing agent 14’ may be water. In an example, the detailing agent 14’ of the multi-fluid kit 20 consists of the second liquid vehicle. In another example, the detailing agent 14’ includes the second liquid vehicle and one or more additional components (e.g., additives), such as any co-solvent(s), surfactant(s), anti-kogation agent(s), antimicrobial agent(s), chelating agent(s), and/or humectant(s) described herein in reference to the detailing agent 14 of the multi-fluid kit 10.

[0107] Flame-retardant Agent 16

[0108] In addition to the fusing agent 12’ and the detailing agent 14’, the multi-fluid kit 20 shown in Fig. 2 also includes the flame-retardant agent 16.

[0109] The flame-retardant agent 16 generally includes a cyclodextrin compound and a third liquid vehicle. In an example, the flame-retardant agent 16 consists of the cyclodextrin compound and the third liquid vehicle, with no other components. In other examples, the flame-retardant agent 16 includes the cyclodextrin compound, the third 86324975

37 liquid vehicle, and one or more additional components (i.e. , additives), such as any of the co-solvent(s), surfactant(s), anti-kogation agent(s), antimicrobial agent(s), chelating agent(s), and/or humectant(s) described herein in reference to the fusing agents 12, 12’ and the detailing agents 14, 14’. Each of the components of the flameretardant agent 16 will now be described.

[0110] Cyclodextrin Compound

[0111 ] The cyclodextrin compound included in the flame-retardant agent 16 may be any example of the flame-retardant cyclodextrin compound 15 described herein in reference to the multi-fluid kit 10. As such, the cyclodextrin compound that is included in the flame-retardant agent 16 (of the multi-fluid kit 20) may be selected from the group consisting of o-cyclodextrin, [3-cyclodextrin, y-cyclodextrin, hydroxypropyl-[3- cyclodextrin, hydroxyethyl-a-cyclodextrin, carboxymethyl-a-cyclodextrin, carboxy- methyl-[3-cyclodextrin, and a combination thereof. In a specific example, the cyclodextrin compound is hydroxypropyl-[3-cyclodextrin.

[0112] The cyclodextrin compound may be present in the flame-retardant agent 16 in an amount ranging from about 0.1 wt% to about 30 wt%, based on the total weight of the flame-retardant agent 16. In an example, the cyclodextrin compound is present in the flame-retardant agent 16 an amount ranging from about 15 wt% to about 25 wt%, based on the total weight of the flame-retardant agent 16. In one specific example, the cyclodextrin compound is present in the flame-retardant agent 16 in an amount of about 20.0 wt%.

[0113] The cyclodextrin compound may be incorporated into the (third) liquid vehicle of the flame-retardant agent 16, e.g., during formation of the flame-retardant agent 16.

[0114] Flame-retardant Agent Liquid Vehicle(s)

[0115] The “third liquid vehicle” refers to the liquid in which the cyclodextrin compound(s) is/are dispersed or dissolved to form the flame-retardant agent 16. Any example of the various aqueous/non-aqueous solvents and co-solvents described herein in reference to the fusing agents 12, 12’ and to the detailing agents 14, 14’ may be used in the third liquid vehicle of the flame-retardant agent 16. In some examples, 86324975

38 the third liquid vehicle (of the flame-retardant agent 16) includes water alone, another aqueous solvent alone, or a non-aqueous solvent alone, with no other components. [0116] As described, in other examples, the third liquid vehicle includes additional components, depending, in part, upon the applicator that is to be used to dispense the flame-retardant agent 16. Examples of other suitable flame-retardant agent 16 components include any of the co-solvent(s), surfactant(s), antimicrobial agent(s), anti- kogation agent(s), chelating agent(s), and/or humectant(s) described herein in reference to the fusing agents 12, 12’ and the detailing agents 14, 14’. Further, any of these components may be incorporated into the third liquid vehicle of the flameretardant agent 16 in the amounts described herein in reference to the various agents 12, 12’, 14, 14’, with the understanding that the wt% of the components will be based on a total weight of the flame-retardant agent 16.

[0117] Either of the multi-fluid kit 10 or the multi-fluid kit 20 may be used in various three-dimensional printing methods to form 3D objects/object layers having flameretardant properties. These methods utilize a build material composition, which will now be described.

[0118] Build Material Composition

[0119] The build material composition that can be used with the multi-fluid kits 10, 20 disclosed herein includes a polymeric build material (and thus is sometimes referred to herein as a “polymeric build material composition.” Examples of suitable polymeric materials include a polyamide (PAs) (e.g., PA 11 / nylon 11 , PA 12 / nylon 12, PA 6 / nylon 6, PA 8 / nylon 8, PA 9 / nylon 9, PA 66 / nylon 66, PA 612 / nylon 612, PA 812 / nylon 812, PA 912 / nylon 912, etc.), a thermoplastic polyamide (TPA), a thermoplastic polyurethane (TPU), a styrenic block copolymer (TPS), a thermoplastic polyolefin elastomer (TPO), a thermoplastic vulcanizate (TPV), thermoplastic copolyester (TPC), a polyether block amide (PEBA), and a combination thereof.

[0120] In some examples, the polymeric build material may be in the form of a powder. In other examples, the polymeric build material may be in the form of a powder-like material, which includes, for example, short fibers having a length that is greater than its width. In some examples, the powder or powder-like material may be 86324975

39 formed from — or may include — short fibers that may, for example, have been cut into short lengths from long strands or threads of material.

[0121 ] The polymeric build material may be made up of similarly sized particles and/or differently sized particles. In an example, the average particle size of the polymeric build material ranges from about 2 pm to about 225 pm. In another example, the average particle size of the polymeric build material ranges from about 10 pm to about 130 pm. The term “average particle size”, as used herein, may refer to a number-weighted mean diameter or a volume-weighted mean diameter of a particle distribution of the material being referred to.

[0122] When the polymeric build material is a polyamide, the polymer may have a wide processing window of greater than 5°C, which can be defined by the temperature range between the melting point and the re-crystallization temperature. In an example, the polymer may have a melting point ranging from about 50°C to about 300°C. As other examples, the polymer may have a melting point ranging from about 155°C to about 225°C, from about 155°C to about 215°C, about 160°C to about 200°C, from about 170°C to about 190°C, or from about 182°C to about 189°C. As still another example, the polymer may be a polyamide having a melting point of about 180°C.

[0123] When the polymeric build material is a thermoplastic elastomer, the thermoplastic elastomer may have a melting range within the range of from about 130°C to about 250°C. In some examples (e.g., when the thermoplastic elastomer is a polyether block amide), the thermoplastic elastomer may have a melting range of from about 130°C to about 175°C. In some other examples (e.g., when the thermoplastic elastomer is a thermoplastic polyurethane), the thermoplastic elastomer may have a melting range of from about 130°C to about 180°C or a melting range of from about 175°C to about 210°C.

[0124] In some examples, the polymeric build material does not substantially absorb radiation having a wavelength within the range of 300 nm to 1 00 nm. The phrase “does not substantially absorb” means that the absorptivity of the polymeric build material at a particular wavelength is 25% or less (e.g., 20%, 10%, 5%, etc.) 86324975

40

[0125] In some examples, in addition to the polymeric build material, the build material composition may include an antioxidant, a whitener, an antistatic agent, a flow aid, or a combination thereof. While several examples of these additives are provided, it is to be understood that these additives are selected to be thermally stable (i.e. , will not decompose) at the 3D printing temperatures.

[0126] Antioxidant(s) may be added to the build material composition to prevent or slow molecular weight decreases of the polymeric build material and/or to prevent or slow discoloration (e.g., yellowing) of the polymeric build material by preventing or slowing oxidation of the polymeric build material. In some examples, the polymeric material may discolor upon reacting with oxygen, and this discoloration may contribute to the discoloration of the build material composition. The antioxidant may be selected to minimize discoloration. In some examples, the antioxidant may be a radical scavenger. In these examples, the antioxidant may include IRGANOX® 1098 (benzenepropanamide, N, N'-1 ,6-hexanediylbis(3,5-bis(1 ,1-dimethylethyl)-4-hydroxy)), IRGANOX® 254 (a mixture of 40% triethylene glycol bis(3-tert-butyl-4-hydroxy-5- methylphenyl), polyvinyl alcohol and deionized water), and/or other sterically hindered phenols. In other examples, the antioxidant may include a phosphite and/or an organic sulfide (e.g., a thioester). The antioxidant may be in the form of fine particles (e.g., having an average particle size of 5 pm or less) that are dry blended with the polymeric build material 16. In an example, the antioxidant may be included in the build material composition in an amount ranging from about 0.01 wt% to about 5 wt%, based on a total weight of the build material composition. In other examples, the antioxidant may be included in the build material composition in an amount ranging from about 0.01 wt% to about 2 wt% or from about 0.2 wt% to about 1 wt%, based on the total weight of the build material composition.

[0127] Whitener(s) may be added to the build material composition to improve visibility. Examples of suitable Whiteners include titanium dioxide (Tit ), zinc oxide (ZnO), calcium carbonate (CaCOs), zirconium dioxide (ZrC ), aluminum oxide (AI2O3), silicon dioxide (SiCte), boron nitride (BN), and combinations thereof. In some examples, a stilbene derivative may be used as the whitener and a brightener. In these examples, the temperature(s) of the 3D printing process may be selected so that 86324975

41 the stilbene derivative remains stable (i.e. , the 3D printing temperature does not thermally decompose the stilbene derivative). In an example, any example of the whitener may be included in the build material composition in an amount ranging from greater than 0 wt% to about 10 wt%, based on the total weight of the build material composition.

[0128] Antistatic agent(s) may be added to the build material composition to suppress tribo-charging. Examples of suitable antistatic agents include aliphatic amines (which may be ethoxylated), aliphatic amides, quaternary ammonium salts (e.g., behentrimonium chloride or cocamidopropyl betaine), esters of phosphoric acid, polyethylene glycolesters, or polyols. Some suitable commercially available antistatic agents include HOSTASTAT® FA 38 (natural based ethoxylated alkylamine), HOSTASTAT® FE2 (fatty acid ester), and HOSTASTAT® HS 1 (alkane sulfonate), each of which is available from Clariant Int. Ltd.). In an example, the antistatic agent is added in an amount ranging from greater than 0 wt% to less than 5 wt%, based on the total weight of the build material composition.

[0129] Flow aid(s) may be added to improve the coating flowability of the build material composition. Flow aids may be particularly beneficial when the build material composition has an average particle size less than 25 pm. The flow aid improves the flowability of the build material composition by reducing the friction, the lateral drag, and the tribocharge buildup (by increasing the particle conductivity). Examples of suitable flow aids include aluminum oxide (AI2O3), tricalcium phosphate (E341 ), powdered cellulose (E460(ii)), magnesium stearate (E470b), sodium bicarbonate (E500), sodium ferrocyanide (E535), potassium ferrocyanide (E536), calcium ferrocyanide (E538), bone phosphate (E542), sodium silicate (E550), silicon dioxide (E551), calcium silicate (E552), magnesium trisilicate (E553a), talcum powder (E553b), sodium aluminosilicate (E554), potassium aluminum silicate (E555), calcium aluminosilicate (E556), bentonite (E558), aluminum silicate (E559), stearic acid (E570), and polydimethylsiloxane (E900). In an example, the flow aid is added in an amount ranging from greater than 0 wt% to less than 5 wt%, based upon the total weight of the build material composition. 86324975

42

[0130] The build material composition may be used with either of the multi-fluid kit 10 or the multi-fluid kit 20 in various 3D printing methods. Examples of these 3D printing methods will now be described.

[0131 ] Methods of 3D Printing

[0132] A flow diagram of an example of a method of three-dimensional printing that utilizes the components of the multi-fluid kit 10 or the components of the multi-fluid kit 20 is shown in Fig. 3. As shown in the figure, the method 100 generally involves applying a build material composition to form a build material layer (shown at reference numeral 102); depositing a fusing agent 12, 12’ on at least a portion of the build material layer, the fusing agent 12, 12’ including an electromagnetic energy absorber and a first liquid vehicle (shown at reference numeral 104); depositing a flame-retardant cyclodextrin compound 15 on the at least the portion (shown at reference numeral 106); and exposing the build material layer to electromagnetic radiation, thereby coalescing the build material layer at the at least the portion to form a 3D object layer (shown at reference numeral 108).

[0133] The manner in which the method 100 is performed will vary based upon whether the multi-fluid kit 10 or the multi-fluid kit 20 is being utilized. This is because the multi-fluid kit 10 includes the fusing agent 12 and the detailing agent 14, either or both of which may include the flame-retardant cyclodextrin compound 15, whereas the multi-fluid kit 20 includes the fusing agent 12’, the detailing agent 14’, and the flameretardant agent 16. As described, in the multi-fluid kit 20, the flame-retardant agent 16 includes the cyclodextrin compound (i.e., flame-retardant cyclodextrin compound 15), whereas the cyclodextrin compound is absent from the fusing agent 12’ and from the detailing agent 14’.

[0134] An example of the method 100 that utilizes the multi-fluid kit 10 is schematically depicted in Fig. 4.

[0135] As shown in Fig. 4, a layer 26 of the build material composition 24 is applied on a build area platform 22. A printing system may be used to apply the build material composition 24. The printing system may include the build area platform 22, a build 86324975

43 material supply 28 containing the build material composition 24, and a build material distributor 30.

[0136] The build area platform 22 receives the build material composition 24 from the build material supply 28. The build area platform 22 may be moved in the directions as denoted by the arrows 32, 34, e.g., along the x-axis and the y-axis respectively, so that the build material composition 24 may be delivered to the build area platform 22 or to a previously formed build material layer 26. In an example, when the build material composition 24 is to be delivered, the build area platform 22 may be programmed to advance enough so that the build material distributor 30 can push the build material composition 24 onto the build area platform 22 to form a substantially uniform layer 26 of the build material composition 24 thereon. The build area platform 22 may also be returned to its original position, for example, when a new part is to be built.

[0137] The build material supply 28 may be a container, bed, or other surface that is to position the build material composition 24 between the build material distributor 30 and the build area platform 22. The build material supply 28 may include heaters so that the build material composition 24 is heated to a supply temperature ranging from about 25°C to about 150°C (heaters not shown in Fig. 4). In these examples, the supply temperature may depend, in part, on the build material composition 24 used and/or the 3D printer used. As such, the range provided is one example, and higher or lower temperatures may be used.

[0138] The build material distributor 30 may be moved in the directions as denoted by the arrow 32, e.g., along the x-axis, over the build material supply 28 and across the build area platform 22 to spread the build material composition 24 over the build area platform 22 and form the layer 26. The build material distributor 30 may also be returned to a position adjacent to the build material supply 28 following the spreading of the build material composition 24. The build material distributor 30 may be a blade (e.g., a doctor blade), a roller, a combination of a roller and a blade, and/or any other device capable of spreading the build material composition 24 over the build area platform 22. For instance, the build material distributor 30 may be a counter-rotating roller. In some examples, the build material supply 28 or a portion of the build material 86324975

44 supply 28 may translate along with the build material distributor 30 such that build material composition 24 is delivered continuously to the build area platform 22 rather than being supplied from a single location at the side of the printing system as depicted in Fig. 4.

[0139] The build material supply 28 may supply the build material composition 24 into a position so that it is ready to be spread onto the build area platform 22. The build material distributor 30 may spread the supplied build material composition 24 onto the build area platform 22. The controller (not shown) may process “control build material supply” data, and in response, control the build material supply 28 to appropriately position the particles of the build material composition 24, and may process “control spreader” data, and in response, control the build material distributor 30 to spread the build material composition 24 over the build area platform 22 to form the layer 26 of the build material composition 24 thereon. In Fig. 4, one build material layer 26 has been formed.

[0140] The layer 26 has a substantially uniform thickness across the build area platform 22. In an example, the build material layer 26 has a thickness ranging from about 50 pm to about 120 pm. In another example, the thickness of the build material layer 26 ranges from about 30 pm to about 300 pm. It is to be understood that thinner or thicker layers may also be used. For example, the thickness of the build material layer 26 may range from about 20 pm to about 500 pm. The layer thickness may be about 2x (i.e. , 2 times) the average diameter of the build material composition particles at a minimum for finer part definition. In some examples, the layer thickness may be about 1.2x the average diameter of the build material composition particles.

[0141 ] After the build material composition 24 has been applied, and prior to further processing, the build material layer 26 may be exposed to heating. In an example, the heating temperature may be below the melting point or melting range of the polymeric material of the build material composition 24. As examples, the pre-heating temperature may range from about 5°C to about 50°C below the melting point or the lowest temperature of the melting range of the polymeric material. In an example, the pre-heating temperature ranges from about 50°C to about 205°C. In still another example, the pre-heating temperature ranges from about 100°C to about 190°C. It is 86324975

45 to be understood that the pre-heating temperature may depend, in part, on the build material composition 24 used. As such, the ranges provided are some examples, and higher or lower temperatures may be used.

[0142] Pre-heating the layer 26 may be accomplished by using any suitable heat source that exposes all the build material composition 24 in the layer 26 to the heat. Examples of the heat source include a thermal heat source (e.g., a heater (not shown) integrated into the build area platform 22 (which may include sidewalls)) or a radiation source 30.

[0143] As shown in Fig. 4, after the layer 26 is formed, and in some instances is pre-heated, the fusing agent 12 is selectively applied on at least some of the build material composition 24 in the layer 26 using an applicator 40 to form (a) patterned portion(s) 18.

[0144] The applicator 40 may be a thermal inkjet printhead, a piezoelectric printhead, a continuous inkjet printhead, or any other suitable device that can be used to selectively deposit the fusing agent 12 onto the build material layer 26 at the portion(s) 18.

[0145] When it is desirable to form a white, colored, or slightly tinted object layer 38, the primer fusing agent may be used to pattern the build material composition 24 at the portion(s) 18 (rather than the core fusing agent). The primer fusing agent is clear or slightly tinted, and thus the resulting 3D object layer 38 may appear white or the color of the build material composition 24. When it is desirable to form a darker color or black object layer 38, the core fusing agent may be used. The core fusing agent is dark or black, and thus the resulting 3D object layer 38 may appear grey, black or another dark color. In other instances, both the primer and core fusing agents may be applied to the layer 26 in respective sections of the portion(s) 18. For example, the core fusing agent may be applied to a central or innermost section of the portion 18 and the primer fusing agent mat be applied to the outermost sections of the portion 18. The core fusing agent may provide additional mechanical strength to the resulting 3D object layer, while the primer fusing agent can mask the dark color of the core fusing agent. 86324975

46

[01 6] The amount of the fusing agent 12 that is applied per unit of the build material composition 24 in the patterned portion(s) 18 may be sufficient to absorb and convert enough electromagnetic radiation so that the build material composition 24 in the patterned portion(s) 18 will coalesce/fuse. The amount of the fusing agent 12 that is applied per unit of the build material composition 24 may depend, at least in part, on the energy absorber used, the energy absorber loading in the fusing agent 12, and the build material composition 24 used. In particular, the concentration of the energy absorber in the fusing agent 12 can be considered. This concentration can be used to determine how much fusing agent 12 to apply to achieve a weight ratio of fusing agent 12 to build material composition 24 for acceptable layer-by-layer fusing. Thus, if applying the fusing agent 12 (10 wt%) to the build material composition 24 (90 wt%) at about a 1 :9 weight ratio, then the energy absorber to build material composition 24 weight ratio (as applied) can be from about 1 :9000 to about 1 :30. If more (up to 20 wt%) or less (down to 5 wt%) of the fusing agent 12 is applied to the build material composition 24, then these ratios can be adjusted accordingly. That stated, the weight ratio of the energy absorber to the build material composition 24 (as applied) in some more specific examples can be from about 1 : 1000 to about 1 :80, from about 1 :800 to about 1 :100, or from about 1 :500 to about 1 :150, as examples.

[0147] As described herein, the fusing agent 12 may include the flame-retardant cyclodextrin compound 15. As such, in some examples, the flame-retardant cyclodextrin compound 15 is included within the fusing agent 12, and the depositing of the fusing agent 12 and the depositing of the flame-retardant cyclodextrin compound 15 is performed simultaneously. When included in the fusing agent 12, the flameretardant cyclodextrin compound 15 imparts properties of flame-retardancy to the build material composition 24 within the portion(s) 18 (e.g., after the fusing agent 12 is applied thereto).

[0148] As shown in Fig. 4, portion(s) 36 of the build material composition 24 are patterned with the detailing agent 14 (using an applicator 40’) and are not patterned with the fusing agent 12. Thus, these portion(s) 36 are not to become part of the final 3D object layer 38. Thermal energy generated during radiation exposure may propagate into the surrounding portion(s) 36 that do not have the fusing agent 12 86324975

47 applied thereto. The detailing agent 14 aids in inhibiting the propagation of thermal energy into the portion(s) 36 during radiation exposure, and thus helps to prevent the coalescence of the build material composition 24 within the portion(s) 36. In examples, the portion(s) 36 of the build material composition 24 that are patterned with the detailing agent 14 form an edge region of a 3D object layer 38 that will be formed. [0149] The detailing agent 14 may also be applied in the portion(s) 18 when it is desirable to tailor (reduce) the extent of fusing. This may be desirable when a more pliable 3D object is to be formed.

[0150] The applicator 40’ may be any suitable example of the applicator described herein, such a thermal inkjet printhead, a piezoelectric printhead, or a continuous inkjet printhead.

[0151 ] As described, the flame-retardant cyclodextrin compound 15 may be included in the detailing agent 14. In some examples, the detailing agent 14 may be applied with the fusing agent 12 in the portion(s) 18 in order to impart the flameretardant properties to the build material composition 24 within the portion(s) 18 (e.g., after coalescence). In this example, the detailing agent 14 may also be applied within the portion(s) 36 to prevent coalescence. This will introduce some of the flameretardant cyclodextrin compound 15 to the portion(s) 36, at least some of which may remain in the build material composition 24 if the portion(s) 36 are recycled. As such, in an example, depositing the flame-retardant cyclodextrin compound 15 involves depositing a detailing agent 14 that includes the flame-retardant cyclodextrin compound 15 therein.

[0152] In some instances, the flame-retardant cyclodextrin compound 15 is included in both the fusing agent 12 and in the detailing agent 14. In these examples, flame-retardant cyclodextrin compound 15 imparts properties of flame-retardancy to the build material composition 24 within the portion(s) 18 of the layer 26 and within the portion(s) 36 of the layer 26.

[0153] After the fusing agent 12 and the detailing agent 14 are selectively applied in the specific portion(s) 18, 36 of the layer 26, the entire layer 26 of the build material composition 24 is exposed to electromagnetic radiation (shown as EMR in Fig. 4). 86324975

48

[0154] The electromagnetic radiation is emitted from the radiation source 40. The length of time the electromagnetic radiation is applied for, or energy exposure time, may be dependent, for example, on one or more of: characteristics of the radiation source 40, characteristics of the build material composition 24, and/or characteristics of the fusing agent 12 or the detailing agent 14. In an example, a single point of the build material layer 26 is exposed to electromagnetic radiation for a period of time ranging from 0.01 second to 1 second.

[0155] It is to be understood that the electromagnetic radiation exposure may be accomplished in a single radiation event or in multiple radiation events. In an example, the exposing of the build material composition 24 is accomplished in multiple radiation events. In a specific example, the number of radiation events ranges from 3 to 8. In still another specific example, the exposure of the build material composition 24 to electromagnetic radiation may be accomplished in 3 radiation events. It may be desirable to expose the build material composition 24 to electromagnetic radiation in multiple radiation events to sufficiently elevate the temperature of the build material composition 24 in the patterned portion(s) 18, without overheating the build material composition 24 in the portion(s) 36.

[0156] The fusing agent 12 enhances the absorption of the radiation in the portion(s) 18, converts the absorbed radiation to thermal energy, and promotes the transfer of the thermal heat to the build material composition 24 in contact therewith. In an example, the fusing agent 12 sufficiently elevates the temperature of the build material composition 24 in the portion(s) 18 to a temperature above the melting point or within the melting range of the polymeric material in the build material composition 24, and thus coalescing/fusing (e.g., thermal merging, melting, binding, etc.) of the build material composition 24 takes place during EMR (electromagnetic radiation) exposure. The application of the electromagnetic radiation forms the 3D object layer 38. When the flame-retardant cyclodextrin compound 15 is included in the fusing agent 12 (and thus becomes a part of the 3D object layer 38 being formed), the 3D object layer 38 exhibits properties of flame-retardancy. When the flame-retardant agent 15 is included in the detailing agent 14, flame retardancy can be introduced to a 86324975

49 part of the 3D object layer 38 and/or an edge region of the 3D object layer 38 being formed, depending upon where the detailing agent 14 is applied.

[0157] In some examples, the electromagnetic radiation has a wavelength ranging from 800 nm to 4000 nm, or from 800 nm to 1400 nm, or from 800 nm to 1200 nm. Radiation having wavelengths within the provided ranges may be absorbed (e.g., 80% or more of the applied radiation is absorbed) by the fusing agent 12, 26’ and may heat the build material composition 24 in contact therewith, and may not be substantially absorbed (e.g., 25% or less of the applied radiation is absorbed) by the build material composition 24 in portion(s) 36.

[0158] After the 3D object layer 38 is formed, additional 3D object layer(s) 38 may be formed thereon to create an example of the 3D object. To form the next layer, additional build material composition 24 may be applied on the already-formed 3D object layer 38. The fusing agent 12 is then selectively applied on at least a portion of the additional build material composition 24, according to the 3D object model (e.g., portion(s) 18). The detailing agent 14 is also selectively applied in any area of the additional build material composition 24 where coalescence is not desirable, such as additional portion(s) 36, which may form edge regions of the 3D object being formed. As described herein, the detailing agent 14 may also or alternatively be applied to the portion(s) 18. The flame-retardant cyclodextrin compound 15 may be present in the fusing agent 12 and/or the detailing agent 14. After the agents 12, 14 are applied, the entire layer 26 of the additional build material composition 24 is exposed to electromagnetic radiation in the manner described herein. The application of additional build material composition 24 and the selective application of the agents 12, 14, the electromagnetic radiation exposure may be iteratively repeated for a predetermined number of cycles to form the final 3D object, in accordance with a 3D object model. All, or some of, the final 3D object will exhibit properties of flame- retardancy.

[0159] An example of the method 100 that utilizes the multi-fluid kit 20 is schematically depicted in Fig. 5. In this example, the fusing agent 12’, the detailing agent 14’, and/or the flame-retardant agent 16 of the multi-fluid kit 20 may be utilized. 86324975

50

[0160] This example method may be performed in accordance with the method described herein that utilizes the components of the multi-fluid kit 10 (i.e. , the method depicted in Fig. 4). However, in this example, the flame-retardant cyclodextrin compound 15 is not included in the fusing agent 12’ or in the detailing agent 14’ (as described herein). Rather, the separate flame-retardant agent 16 includes the flameretardant cyclodextrin compound 15. As such, in this example of the method 100, the depositing of the flame-retardant cyclodextrin compound 15 involves depositing a flame-retardant agent 16 that includes the flame-retardant cyclodextrin compound therein.

[0161 ] The flame-retardant agent 16 may be applied to the portion(s) 18 of the build material layer 26 where the fusing agent 12’, alone or in combination with the detailing agent 14’, is/are to be applied. The flame-retardant agent 16 may additionally or alternatively be applied to the portion(s) 36 of the build material layer 26 where the detailing agent 14’ is to be applied. The flame-retardant agent 16 imparts properties of flame-retardancy to the build material composition 24 (and thus the resulting 3D object layer 38 after EMR exposure) within the portion(s) 18 and/or 36.

[0162] The flame-retardant agent 16 may be applied to the build material composition 24 within the portion(s) 18, 36 using the applicator 40”, which may be any suitable applicator described herein (e.g., a thermal inkjet printhead, a piezoelectric printhead, a continuous inkjet printhead, etc.).

[0163] The amount of the flame-retardant agent 16 that is deposited at the portion(s) 18, 36 will depend, in part, upon the amount of the flame-retardant cyclodextrin compound 15 included therein and/or upon the amount of the fusing agent 12’, the detailing agent 14’, or both agents 12’, 14’ that is/are used in the method. In an example, the amount of the flame-retardant agent 16 that is applied at the portion(s) 18, 36 ranges from about 1 drop/pixel to about 10 drops/pixel, where each drop includes from about 5 ng to about 15 ng of flame-retardant agent 16.

[0164] It is to be understood that in this example, the resultant 3D object layer(s) 38 will have flame-retardant properties at portion(s) 18 where the flame-retardant agent 16 has been applied. 86324975

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[0165] To further illustrate the present disclosure, examples are given herein. It is to be understood that these examples are provided for illustrative purposes and are not to be construed as limiting the scope of the present disclosure.

NON-LIMITING WORKING EXAMPLE

[0166] Two example objects were formed to demonstrate the effectiveness of the flame-retardant cyclodextrin compound, i.e. , when the compound is incorporated into a material that will be used to form 3D printed parts. A comparative object was also formed that did not include a flame-retardant cyclodextrin compound.

[0167] A flame-retardant thermoplastic composition was prepared by dry blending polyamide-12 powder with hydroxypropyl-[3-cyclodextrin (an example of the flameretardant cyclodextrin compound disclosed herein), such that thermoplastic composition included 5 wt% of the hydroxypropyl-p-cyclodextrin. The composition was melted in a silicone mold in an oven by heating at 185°C for three minutes. The temperature was then increased over a period of about 20-30 minutes until reaching a temperature of 220°C. The objects were then held at 220°C in the oven for 5 minutes, before being fast cooled to 165°C. The objects were then removed from the oven.

[0168] The comparative object was formed using a similar process, except that the polyamide-12 of the comparative object was not mixed with the flame-retardant cyclodextrin compound.

[0169] The objects were then burned in a UL94 vertical test rig. The samples were inserted into the frame of the rig and burned for 10 seconds. The objects that included the flame-retardant cyclodextrin compound notably self-extinguished with no flaming drips. These observations were distinguishable from those obtained for the comparative object (i.e., the comparative object did not self-extinguish). A photograph of the objects that included the flame-retardant cyclodextrin compound, after burning, was taken, and a reproduction of this photograph (in black-and-white) is shown in Fig.

6. The photograph demonstrates that the 3D objects resisted burning in the test rig via the formation of a carbon layer at the surface of the objects.

[0170] The flame-retardant cyclodextrin compound was also incorporated into a flame-retardant agent to demonstrate the compound’s ability to be incorporated into a 86324975

52 jettable fluid. The components of this example flame-retardant agent are shown in

Table 1 below:

TABLE 1

[0171 ] The example flame-retardant agent was successfully jetted via a thermal inkjet printhead onto a paper substrate and onto a polymeric powder, which demonstrated the selective jettability of the flame-retardant agent.

[0172] By incorporating the flame-retardant cyclodextrin compound into an inkjettable fluid (e.g., fusing agent, detailing agent, and/or flame-retardant agent), the flame-retardant cyclodextrin compound can be selectively applied to build material where it is desirable to impart flame-retardant properties to the final 3D object and/or to the build material during the 3D printing process.

[0173] It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, from about 0.01 wt% to about 5 wt% should be interpreted to include not only the explicitly recited limits of from about 0.01 wt% to about 5 wt%, but also to include individual values, such as about 0.25 wt%, about 0.55 wt%, about 1 .74 wt%, about 2.03 wt%, about 3.2 wt%, about 4.5 wt%, etc., and sub-ranges, such as from about 0.2 wt% to about 4.8 wt%, from about 1 wt% to about 4 wt%, from about 0.5 wt% to about 3.5 wt%, etc. Furthermore, when “about” is utilized to describe a value, this is meant to encompass minor variations (up to +/- 10%) from the stated value.

[0174] Reference throughout the specification to “one example”, “another example”, “an example”, and so forth, means that a particular element (e.g., feature, structure, 86324975

53 and/or characteristic) described in connection with the example is included in at least one example described herein, and may or may not be present in other examples. In addition, it is to be understood that the described elements for any example may be combined in any suitable manner in the various examples unless the context clearly dictates otherwise.

[0175] In describing and claiming the examples disclosed herein, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0176] While several examples have been described in detail, it is to be understood that the disclosed examples may be modified. Therefore, the foregoing description is to be considered non-limiting.

Claims

86324975 54 What is claimed is:

1 . A multi-fluid kit for three-dimensional printing, comprising: a fusing agent including: an electromagnetic energy absorber; and a first liquid vehicle; a detailing agent including a second liquid vehicle; and a flame-retardant cyclodextrin compound that is included in the fusing agent, or in the detailing agent, or in both the fusing agent and the detailing agent.

2. The multi-fluid kit as defined in claim 1 , wherein the flame-retardant cyclodextrin compound is selected from the group consisting of a-cyclodextrin, [3- cyclodextrin, y-cyclodextrin, hydroxypropyl-[3-cyclodextrin, hydroxyethyl-a-cyclodextrin, carboxymethyl-a-cyclodextrin, carboxy-methyl-p-cyclodextrin, and a combination thereof.

3. The multi-fluid kit as defined in claim 1 , wherein the flame-retardant cyclodextrin compound is included in the fusing agent and is absent from the detailing agent.

4. The multi-fluid kit as defined in claim 1 , wherein the flame-retardant cyclodextrin compound is included in the detailing agent and is absent from the fusing agent.

5. The multi-fluid kit as defined in claim 1 , wherein the flame-retardant cyclodextrin compound is present in the fusing agent or in the detailing agent in an amount ranging from about 0.1 wt% to about 30 wt%, based on a total weight of the fusing agent or of the detailing agent, respectively.

6. A multi-fluid kit for three-dimensional printing, comprising: a fusing agent including: an electromagnetic energy absorber; and 86324975

55 a first liquid vehicle; a detailing agent including a second liquid vehicle; and a flame-retardant agent including: a cyclodextrin compound; and a third liquid vehicle.

7. The multi-fluid kit as defined in claim 6, wherein the cyclodextrin compound is selected from the group consisting of a-cyclodextrin, [3-cyclodextrin, y-cyclodextrin, hydroxypropyl-[3-cyclodextrin, hydroxyethyl-a-cyclodextrin, carboxymethyl-a- cyclodextrin, carboxy-methyl-p-cyclodextrin, and a combination thereof.

8. The multi-fluid kit as defined in claim 6, wherein the cyclodextrin compound is present in the flame-retardant agent in an amount ranging from about 0.1 wt% to about 30 wt%, based on a total weight of the flame-retardant agent.

9. A fusing agent, comprising: an electromagnetic energy absorber; a liquid vehicle; and a flame-retardant cyclodextrin compound.

10. The fusing agent as defined in claim 9, wherein the flame-retardant cyclodextrin compound is selected from the group consisting of a-cyclodextrin, [3- cyclodextrin, y-cyclodextrin, hydroxypropyl-p-cyclodextrin, hydroxyethyl-a-cyclodextrin, carboxymethyl-a-cyclodextrin, carboxy-methyl-|3-cyclodextrin, and a combination thereof.

11 . The fusing agent as defined in claim 9, wherein the flame-retardant cyclodextrin compound is present in fusing agent in an amount ranging from about 0.1 wt% to about 30 wt%, based on a total weight of the fusing agent. 86324975

56

12. A method of three-dimensional printing, comprising: applying a build material composition to form a build material layer; depositing a fusing agent on at least a portion of the build material layer, the fusing agent including an electromagnetic energy absorber and a first liquid vehicle; depositing a flame-retardant cyclodextrin compound on the at least the portion; and exposing the build material layer to electromagnetic radiation, thereby coalescing the build material layer at the at least the portion to form a 3D object layer.

13. The method as defined in claim 12, wherein the flame-retardant cyclodextrin compound is included within the fusing agent, and wherein the depositing of the fusing agent and the depositing of the flame-retardant cyclodextrin compound is performed simultaneously.

14. The method as defined in claim 12, wherein depositing of the flameretardant cyclodextrin compound involves depositing a detailing agent that includes the flame-retardant cyclodextrin compound therein.

15. The method as defined in claim 12, wherein depositing of the flameretardant cyclodextrin compound involves depositing a flame-retardant agent that includes the flame-retardant cyclodextrin compound therein.