High modulus and dispersion stability ink for 3D printing

Abstract

According to one aspect, inks for use in three-dimensional (3D) printing systems are described herein. In certain embodiments, the composite inks described herein include a carrier ink containing a curable material and a solid powder filler dispersed in the carrier ink. In some cases, the composite ink, in the uncured state, has a highly accelerated life test (HALT) score of at least 2 when tested at 65°C for at least 14 days. Furthermore, in some embodiments, the composite ink, in the uncured state, has an average loss factor tan δ of 3 or less, or 2 or less, over an angular frequency range of 0.5 to 5 rad / s.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority pursuant to 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63 / 431,474, filed December 9, 2022, which is incorporated herein by reference in its entirety. [Technical Field]

[0002] This application relates generally to inks for use in additive manufacturing or three-dimensional (3D) printing systems, and more particularly to composite inks that include a carrier ink and a filler dispersed in the carrier ink. [Background technology]

[0003] Some commercially available 3D printers or additive manufacturing systems, such as the ProJet® 3D printer manufactured by 3D Systems of Rock Hill, South Carolina, USA, use inks, also known as build materials, that are jetted as a liquid through a printhead to form various 3D objects, articles, or parts. Other 3D printing systems also use inks that are jetted through a printhead or otherwise dispensed onto a substrate. In some cases, the ink is solid at ambient temperature and changes to a liquid at elevated jetting temperatures. In other cases, the ink is liquid at ambient temperature. Additionally, in some cases, the ink can be cured after dispersing and / or depositing the ink on a substrate. Curing can be achieved using a laser or other electromagnetic radiation source.

[0004] Other 3D printers form 3D articles from reservoirs, vats, or containers of fluid or powdered ink or build material, and in some cases use a binder material or a laser or other light source to selectively solidify or solidify layers of the ink or build material in stages to provide the 3D article.

[0005] Some inks used in additive manufacturing generally require high modulus materials for some applications, such as wind tunnel modeling and low strain applications. Composite inks can provide some desirable properties for specific applications. However, as will be appreciated, some composite or other inks exhibit processing and handling limitations, including, in some cases, relatively poor dispersion stability. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, there is a need for improved inks for 3D printing that have mechanical properties in the cured state that are suitable for a particular application, and high dispersion stability in the uncured or liquid state, while having other properties that make them suitable for use in one or more 3D printing processes and systems, such as stereolithography (SLA) processes and systems and the Figure 4® process and system offered by 3D Systems, Inc. [Means for solving the problem]

[0007] In one aspect, inks for use in additive manufacturing or 3D printing systems are described herein, which, in some embodiments, may offer one or more advantages over conventional inks, particularly composite inks containing solid fillers. For example, in some cases, the inks described herein are well-dispersed, shelf-life stable inks that easily redisperse as needed. Furthermore, in some embodiments, the inks described herein are capable of fully free-radical polymerization and / or do not polymerize using a cationic polymerization pathway. Furthermore, it should be understood that the inks described herein may, in some cases, possess one or more structural or performance properties, either in the uncured or cured state, that provide advantages for the use of the ink in additive manufacturing or 3D printing. For example, in some cases, the inks described herein have a viscosity suitable for additive manufacturing and also provide printed 3D articles with a high modulus.

[0008] In some embodiments, an ink or composite ink for use in the 3D printing systems described herein comprises a carrier ink including a curable material and a solid powder filler dispersed in the carrier ink. Additionally, in some cases, the composite ink, in its uncured state, has a highly accelerated life test (HALT) score of at least 2 when tested at 65°C for at least 14 days, and / or the composite ink, in its uncured state, has an average loss factor tan δ of 3 or less, or 2 or less, over an angular frequency range of 0.5 to 5 rad / s. Additional ink components and characteristics are further described below.

[0009] In another aspect, methods for forming 3D articles by additive manufacturing are described herein. In some embodiments, such methods include selectively depositing a layer of the ink described herein in a fluid state onto a substrate to form a three-dimensional article. The method can further include photocuring the ink. Furthermore, in some embodiments of the methods described herein, the ink is selectively photocured according to preselected computer-aided design (CAD) or other parameters from a digital file representing or corresponding to the 3D article.

[0010] Alternatively, in other embodiments, a method for forming a 3D article by additive manufacturing includes holding an ink described herein in a fluid state in a container and selectively applying energy to the ink in the container to solidify at least a portion of a first fluid layer of the ink, thereby forming a first solidified layer that defines a first cross-section of the article. The method further includes raising or lowering the first solidified layer to provide a second fluid layer of the ink on a surface of the fluid ink in the container, and selectively applying energy to the ink in the container to solidify at least a portion of the second fluid layer of the ink, thereby forming a second solidified layer that defines a second cross-section of the article. The first cross-section and the second cross-section are joined together in the z-direction. As further described herein, the foregoing steps can be repeated any desired number of times necessary to complete the 3D article. Furthermore, in some preferred embodiments, selectively applying energy to the ink in the container includes photocuring the ink.

[0011] In yet another aspect, printed 3D articles are described herein. Such articles can be formed from any of the inks described herein using any of the methods.

[0012] These and other embodiments are described in greater detail in the detailed description that follows.

[0013] The following drawings, which are not necessarily drawn to scale, are provided for illustrative purposes and to aid in understanding the present disclosure. [Brief explanation of the drawings]

[0014] [Figure 1] Perspective view of the components of the HALT score test device [Figure 2] 2 is a perspective side view of the components of FIG. 1, perpendicular to the positions of the components shown in FIG. 1; [Figure 3] HALT Scoring Category Chart [Figure 4] 1. A perspective side view of a component similar to that shown in FIG. 2. [Figure 5] 1 is a plot of storage modulus (G') and loss modulus (G") as a function of angular frequency (rad / s) for a composite ink according to an embodiment described herein. DETAILED DESCRIPTION OF THE INVENTION

[0015] The embodiments described herein can be more readily understood by reference to the following detailed description, drawings, and examples. However, the elements, devices, and methods described herein are not limited to the specific embodiments presented in the detailed description, drawings, and examples. It should be recognized that these embodiments are merely illustrative of the principles of the present disclosure. Many modifications and adaptations will be readily apparent to those skilled in the art without departing from the spirit and scope of the present disclosure.

[0016] Furthermore, all ranges in the present disclosure should be understood to encompass any and all subranges subsumed therein. For example, a range stated as "1.0 to 10.0" should be considered to include any and all subranges beginning with a minimum value of 1.0 or greater and ending with a maximum value of 10.0 or less, such as 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9. Similarly, a range stated as "1 to 10" should be considered to include any and all subranges beginning with a minimum value of 1 or greater and ending with a maximum value of 10 or less, such as 1 to 5, or 4 to 10, or 3 to 7, or 5 to 8.

[0017] All ranges disclosed herein should also be considered to include the endpoints of the range, unless otherwise specified. For example, a range of "between 5 and 10," "from 5 to 10," or "5-10" should generally be considered to include the endpoints of 5 and 10.

[0018] Furthermore, when the phrase "up to" is used in conjunction with a quantity or amount, it should be understood that the amount is at least a detectable quantity or amount (i.e., the amount is non-zero). For example, a material present in an amount "up to" a specified amount may be present from a detectable (non-zero) amount up to and including the specified amount.

[0019] Furthermore, unless the context clearly requires otherwise, the use of the singular forms "a" or "an" should be understood to refer to "one or more" or "at least one."

[0020] The terms "3D printing system," "3D printer," "printing," and the like generally describe various solid freeform fabrication techniques for producing three-dimensional articles or objects by stereolithography (SLA), selective deposition, jetting, fused deposition modeling (FDM), multi-jet modeling (MJM), and other additive manufacturing techniques known or to become known in the art that use build materials or inks to create three-dimensional objects.

[0021] I. Ink for 3D printing In one aspect of the present disclosure, a composite ink for use in a 3D printing system or method is provided. In some embodiments, the composite ink described herein includes a carrier ink including a curable material and a solid powder filler dispersed in the carrier ink. In some cases, the composite ink may further include one or more additional components, such as one or more photoinitiators, polymerization inhibitors or stabilizers, colorants, dispersants, antifoaming or degassing agents (also known as dealators), or a combination of two or more of the above. Each component of the composite ink is further described below.

[0022] In particular, the composite inks of the present disclosure can have compositions that provide high stability and ease of use in 3D printing. For example, in some cases, the composite inks described herein have a highly accelerated life test (HALT) score of at least 2 when tested in the uncured state at 65°C for at least 14 days. In some examples, the composite inks have a HALT score of 3 when tested at 65°C for at least 14 days. HALT scores are further described in Example 1 below.

[0023] Additionally, in some embodiments, the composite inks described herein have, in the uncured state, an average loss factor, tan δ, of 3 or less, or 2 or less, over an angular frequency range of 0.5 to 5 rad / s. For reference purposes herein, "tan δ" refers to the tangent of δ and is equal to G" / G'. As will be understood by those skilled in the art, G' is the storage modulus (also known as the elastic modulus) and G" is the loss modulus (also known as the viscous modulus) of the composite ink as a function of angular frequency, as further described herein and calculated in ASTM D4440-15 (Standard Test Methods for Plastics: Dynamic Mechanical Properties - Melt Rheology). As will be understood by those skilled in the art, G" and G' are derived from the phase shift between oscillatory stress and strain. A strain is applied and stress is measured (e.g., using a torque sensor). The parameters tan δ, G", and G' are further described in AN004 ("Viscosity and Dynamic Mechanical Testing") by A. Franck, TA Instruments. According to some embodiments, the compositional parameters of the composite inks described herein are selected (as described herein) to provide a small or minimal loss factor tan δ, and as will be understood by those skilled in the art, the loss factor δ is considered a structural feature of the composite ink.

[0024] Both the HALT score and the loss factor tan δ are related to the dispersion stability of the composite inks described herein. In some embodiments, the composite inks described herein can have both a HALT score described herein and a loss factor tan δ described herein. Alternatively, in other cases, the composite ink can have only a HALT score described herein or only a loss factor tan δ described herein, with the other parameter (HALT score or loss factor tan δ) being outside the range described herein. Furthermore, in some embodiments, the composite inks described herein can include particles that, in the uncured state, have good dispersibility within the composite ink, can be storage stable, and the particles in the composite ink can be easily redispersed by agitation when redispersion is required.

[0025] Furthermore, as used throughout this disclosure, the term "uncured" composite ink includes inks containing curable materials or polymerizable components that are not cured, i.e., not polymerized and / or crosslinked, or that are cured (polymerized and / or crosslinked) to a minimal or negligible degree. For example, in some cases, the uncured ink is about 1% or less polymerized or crosslinked, or about 0.5% or less, or about 0.1% or less polymerized or crosslinked. The degree of polymerization or crosslinking can be determined using any protocol or method consistent with the technical objectives of this disclosure, for example, by measuring the percentage of monomer incorporated into the polymer network (e.g., based on the molecular weight of the polymer compared to the molecular weight of the monomer, or based on the total polymer mass compared to the theoretical maximum total polymer mass) or by measuring the amount of unincorporated monomer. When multiple methods are used to determine the degree of polymerization or crosslinking, the results of these methods can be averaged to arrive at the percentages described herein. It should be further understood that the degree of polymerization or crosslinking described herein is different from the "degree of polymerization," which is defined as the number of repeating units in a polymer molecule.

[0026] Additionally, the composite inks described herein, in some embodiments, have particular flow properties that provide one or more advantages for 3D printing. For example, in some cases, the composite inks described herein are not Bingham fluids (uncured) at 30°C. Furthermore, in some examples, the composite inks described herein (uncured) have a shear viscosity of 5000 cps or less at 30°C, based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3. In some cases, the composite inks described herein have a shear viscosity of 3000 cps or less or 2000 cps or less at 30°C, based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3. In some implementations, the composite inks described herein have a shear viscosity of 500-1500 cps at 30°C, based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3.

[0027] Thus, in some cases, the composite inks described herein, including their uncured states, can have one or more structural parameters that overcome certain use limitations of some other materials for 3D printing. For example, in some cases, composite inks or build materials according to the present disclosure can overcome limitations such as limited particle dispersion stability (which may limit shelf life), high viscosity (which may limit use in 3D printer pumping and leveling requirements), and / or uncontrollable curing behavior associated with cationic polymerization chemistry (which may limit print resolution).

[0028] Referring now in more detail to the specific components of the composite inks described herein, composite inks according to the present disclosure can include various components in varying amounts. It should be understood that the total amount of all components of the composite inks described herein generally amounts to 100% by weight of the composite ink in a given instance. Similarly, it should be understood that all components of the carrier inks described herein generally amount to 100% by weight of the carrier ink in a given instance.

[0029] As one component, the composite inks described herein include a carrier ink, which includes a curable material. The carrier ink may also be referred to as a base ink. Any curable material not inconsistent with the objectives of the present disclosure may be used in the carrier inks or base inks described herein. For example, in some embodiments, the curable material of the carrier ink includes one or more monomeric curable materials and / or one or more oligomeric curable materials. Furthermore, in some cases, the curable material of the carrier ink includes a combination of one or more monomeric curable materials and one or more oligomeric curable materials.

[0030] For purposes of reference herein, a curable material includes a chemical species that includes one or more curable or polymerizable moieties. For purposes of reference herein, a "polymerizable moiety" includes a moiety that can be polymerized or cured to provide a printed 3D article or object. Such polymerization or curing can be carried out in any manner consistent with the objectives of the present disclosure. In some embodiments, for example, polymerization or curing includes irradiating the polymerizable or curable material with electromagnetic radiation having sufficient energy to initiate a polymerization or crosslinking reaction. For example, ultraviolet (UV) radiation can be used in some cases. Thus, in some examples, the polymerizable moiety includes a photopolymerizable or photocurable moiety, such as a UV-polymerizable moiety. In some embodiments, the curable materials described herein are photopolymerizable or photocurable in the wavelength range of about 300 nm to about 400 nm or about 320 nm to about 380 nm. Alternatively, in other examples, the curable material is photopolymerizable in the visible wavelengths of the electromagnetic spectrum.

[0031] Additionally, the polymerization reaction may optionally include a free radical polymerization reaction, such as between unsaturated points, including ethylenically unsaturated points where a carbon-carbon double bond is present. Other polymerization reactions may also be used. As will be appreciated by those skilled in the art, the polymerization reaction used to polymerize or cure the curable materials described herein may include the reaction of multiple "monomers" or chemical species having one or more functional groups or moieties that can react with each other to form one or more covalent bonds.

[0032] One non-limiting example of a polymerizable moiety of the curable materials described herein is an ethylenically unsaturated moiety such as a vinyl moiety, an allyl moiety, or a (meth)acrylate moiety, where the term "(meth)acrylate" throughout this disclosure includes acrylate or methacrylate or mixtures or combinations thereof.

[0033] The "oligomeric" species included in the oligomeric curable materials described herein are themselves polymers or oligomers and have relatively high molecular weights or relatively high viscosities. These species can also undergo further polymerization, for example, through one or more unsaturated points as described herein. The population of oligomeric species in the oligomeric curable materials described herein can have a variety of molecular structures and / or chemical formulas throughout the population (e.g., as indicated by the specific mass of a urethane acrylate having a non-uniform molecular weight distribution, or the specific mass of an ethoxylated polyethylene glycol having a distribution of ethylene glycol units and / or a distribution of ethoxy units within the population). The weight-average molecular weight of the oligomeric curable materials described herein generally ranges from about 500 to 6,000. Furthermore, in some cases, the oligomeric curable materials of the inks described herein contain one or more ethylenically unsaturated species having a dynamic viscosity of 125,000 to 250,000 cP at 50°C, as measured according to ASTM D2983. In some preferred embodiments, the oligomeric curable material comprises one or more ethylenically unsaturated species having a dynamic viscosity of 150,000 to 200,000 cP at 50° C., as measured according to ASTM D2983. Without intending to be bound by theory, it is believed that this combination of molecular weight and viscosity, when an oligomeric curable material is used, contributes to the achievement of the inventive technical effects of the inks described herein.

[0034] In contrast to "oligomeric" species, the "monomer" species included in the monomer-curable materials described herein are not themselves polymers or oligomers and have relatively low molecular weights or relatively low viscosities. The "monomer" species included in the monomer-curable materials may have a consistent or well-defined molecular structure and / or chemical formula across a population (e.g., as may be represented by a specific mass of ethoxylated (4) bisphenol A diacrylate or a specific mass of the above-mentioned curable monomer). Furthermore, in some embodiments, the monomer-curable materials described herein have a viscosity of 500 centipoise (cP) or less at 25° C., as measured according to ASTM D2983, and / or a molecular weight of less than 500, less than 400, or less than 300.

[0035] Additionally, the oligomeric and / or monomeric curable materials described herein can include monofunctional, difunctional, trifunctional, tetrafunctional, pentafunctional, or higher functional curable species. For purposes of reference herein, a "monofunctional" curable species includes a species that contains one curable or polymerizable moiety. Similarly, a "difunctional" curable species includes a species that contains two curable or polymerizable moieties; a "trifunctional" curable species includes a species that contains three curable or polymerizable moieties; a "tetrafunctional" curable species includes a species that contains four curable or polymerizable moieties; and a "pentafunctional" curable species includes a species that contains five curable or polymerizable moieties. Thus, in some embodiments, the monofunctional curable material of the inks described herein comprises a mono(meth)acrylate, the difunctional curable material of the inks described herein comprises a di(meth)acrylate, the trifunctional curable material of the inks described herein comprises a tri(meth)acrylate, and the tetrafunctional curable material of the inks described herein comprises a tetra(meth)acrylate. The pentafunctional curable material of the inks described herein comprises a penta(meth)acrylate. Other monofunctional, difunctional, trifunctional, tetrafunctional, and pentafunctional curable materials can also be used.

[0036] Further, for the avoidance of doubt, the mono-, di-, tri-, tetra-, and penta-functional curable materials may, in some cases, include relatively low molecular weight species, i.e., monomeric species, or relatively high molecular weight species, i.e., oligomeric species.

[0037] Generally, any oligomeric curable material or combination of oligomeric curable materials not inconsistent with the objectives of the present disclosure can be used in the inks described herein. In some cases, the curable oligomeric material comprises a polyester (meth)acrylate oligomer, a urethane (meth)acrylate oligomer, or an epoxy (meth)acrylate oligomer. Furthermore, in some embodiments, the curable oligomeric material described herein comprises an aliphatic polyester urethane acrylate oligomer and / or an acrylate amine oligomer resin such as EBECRYL 7100. In some instances, the curable oligomeric material described herein comprises polypropylene glycol mono(meth)acrylate or polyethylene glycol mono(meth)acrylate. In some embodiments, the curable oligomeric material comprises a monofunctional aliphatic urethane (meth)acrylate. Furthermore, in some cases, the curable oligomeric material comprises a diacrylate and / or dimethacrylate ester of an aliphatic, cycloaliphatic, or aromatic diol, including polyethylene glycol, ethoxylated or propoxylated neopentyl glycol, ethoxylated or propoxylated bisphenol A, ethoxylated or propoxylated bisphenol F, ethoxylated or propoxylated bisphenol S, ethoxylated or propoxylated 1,1,1-trimethylolpropane tri(meth)acrylate, or ethoxylated or propoxylated glycerol tri(meth)acrylate. The oligomeric material may also comprise a cycloaliphatic epoxy.

[0038] Some non-limiting examples of commercially available curable oligomeric materials useful in some embodiments described herein include: an alkoxylated tetrahydrofurfuryl acrylate available from SARTOMER under the tradename SR611; a monofunctional urethane acrylate available from RAHN USA under the tradename GENOMER1122; an aliphatic urethane diacrylate available from ALLNEX under the tradename EBECRYL8402; a multifunctional acrylate oligomer available from DYMAX / BOMAR under the tradename BR-952; an aliphatic polyether urethane acrylate available from DYMAX / BOMAR under the tradename BR-371S; a low molecular weight difunctional aliphatic polyether urethane methacrylate available from BOMAR / DYMAX under the tradename BR-371MS; a low molecular weight difunctional aliphatic polyester urethane acrylate available from BOMAR / DYMAX under the tradename BR-741; and BR-541MB. difunctional aliphatic polyether urethane methacrylate commercially available from BOMAR / DYMAX under the trade name BR-771F; difunctional aliphatic polyester urethane acrylate commercially available from BOMAR / DYMAX under the trade name BR-970H; low viscosity difunctional aliphatic urethane acrylate commercially available from BOMAR / DYMAX under the trade name XR-741MS; and difunctional methacrylate oligomers commercially available from ESSTECH under the trade names EXOTHANE-4, EXOTHANE-8, and EXOTHANE-10. Other commercially available curable oligomeric materials may also be used.

[0039] Urethane (meth)acrylates suitable for use in the inks described herein can be prepared by known methods, typically by reacting a hydroxyl-terminated urethane with acrylic or methacrylic acid to obtain the corresponding urethane (meth)acrylate, or by reacting an isocyanate-terminated prepolymer with a hydroxyalkyl acrylate or methacrylate to obtain the urethane (meth)acrylate, as the case may be. Suitable processes are disclosed, inter alia, in EP-A 114 982 and EP-A 133 908. The weight-average molecular weight of such (meth)acrylate oligomers can, in some cases, be about 500 to 6,000. Urethane (meth)acrylates are also commercially available from SARTOMER under the product names CN980, CN981, CN975, and CN2901, or from BOMAR Specialties Co. under the product name BR-741.

[0040] Oligomeric curable materials, when used, can be present in the carrier inks described herein in any amount consistent with the objectives of the present disclosure. In some cases, the oligomeric curable materials are present in the carrier ink in an amount of 15 to 85 weight percent, in total, based on the total weight of the carrier ink.

[0041] Additionally, any monomer-curable material or combination of monomer-curable materials not inconsistent with the objectives of the present disclosure can be used as the monomer-curable material component of the carrier inks described herein. In some cases, the monomer-curable material of the carrier inks described herein includes one or more types of (meth)acrylates, such as one or more monofunctional, difunctional, trifunctional, tetrafunctional (meth)acrylates, and / or pentafunctional (meth)acrylates. In some embodiments, for example, the monomer-curable material includes methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2- or 3-hydroxypropyl (meth)acrylate, or the like. acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2- or 3-ethoxypropyl (meth)acrylate, tetrahydrofurfuryl methacrylate, isobornyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, cyclohexyl methacrylate, 2-phenoxyethyl acrylate, glycidyl acrylate, isodecyl acrylate, 2-phenoxyethyl (meth)acrylate, lauryl methacrylate, or combinations thereof. In some embodiments, the monomer-curable material comprises one or more of allyl acrylate, allyl methacrylate, triethylene glycol di(meth)acrylate, tricyclodecane dimethanol diacrylate, and cyclohexane dimethanol diacrylate.Additionally, in some cases, the curable material comprises a diacrylate and / or dimethacrylate ester of an aliphatic, alicyclic, or aromatic diol, including 1,3- or 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, tripropylene glycol, 1,4-dihydroxymethylcyclohexane, 2,2-bis(4-hydroxycyclohexyl)propane or bis(4-hydroxycyclohexyl)methane, hydroquinone, 4,4'-dihydroxybiphenyl, bisphenol A, bisphenol F, or bisphenol S. The monomer-curable material described herein can also include 1,1-trimethylolpropane tri(meth)acrylate, pentaerythritol monohydroxytri(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, and / or bis(trimethylolpropane)tetra(meth)acrylate. In some cases, the monomer-curable material comprises an epoxy.

[0042] Additional non-limiting examples of commercially available monomer-curable materials useful in some embodiments described herein include: isobornyl acrylate (IBOA), available from SARTOMER under the tradename SR 506; isobornyl methacrylate, available from SARTOMER under the tradename SR 423A; triethylene glycol diacrylate, available from SARTOMER under the tradename SR 272; triethylene glycol dimethacrylate, available from SARTOMER under the tradename SR 205; tricyclodecane dimethanol diacrylate, available from SARTOMER under the tradename SR 833S; tris(2-hydroxyethyl) isocyanurate triacrylate, available from SARTOMER under the tradename SR 368; 2-phenoxyethyl acrylate, available from SARTOMER under the tradename SR 339; ethoxylated (3 mole) bisphenol A diacrylate, available from SARTOMER under the tradename SR 349; cyclic monofunctional acrylate, available from RAHN USA Corp. under the trade name 1120; dipentaerythritol pentaacrylate, available from SARTOMER under the trade name SR 399LV; hydroxyethyl acrylamide; morpholine acrylamide; cyclic or polycyclic carbonate (meth)acrylate; triallyl isocyanurate, available from SARTOMER under the trade name SR 533; vinylmethyl oxazolidinone, available from BASF under the trade name VMOX; and acetoacetonate ethyl methacrylate. Other commercially available monomer-curable materials can also be used.

[0043] When used, the monomeric curable materials can be present in the carrier inks described herein in any amount consistent with the objectives of the present disclosure. In some cases, the monomeric curable material components are present in the carrier ink in an amount of 15 to 85 wt. %, collectively, based on the total weight of the carrier ink.

[0044] As described above, the curable material of the carrier ink described herein can include various monomeric and / or oligomeric curable materials. For example, in some preferred embodiments, the curable material of the carrier ink includes one or more acrylate, methacrylate, or vinyl species. In other cases, the curable material of the carrier ink includes one or more epoxy species. Furthermore, in some preferred embodiments, all or substantially all of the curable material of the carrier ink is curable by free radical polymerization. For example, in some implementations, at least 90%, at least 95%, or at least 99% by weight of the curable material of the carrier ink is curable by free radical polymerization. The use of free radical polymerization (as opposed to other types of polymerization) can, in some cases, provide one or more advantages for 3D printing.

[0045] The carrier ink of the composite ink described herein also includes, in some embodiments, a photoinitiator component. The photoinitiator component may be operable to initiate polymerization or curing (e.g., by free radical polymerization) of the curable material component of the carrier ink upon exposure to light of an appropriate wavelength. Any photoinitiator not inconsistent with the objectives of the present disclosure may be used in the carrier ink described herein. In some embodiments, the photoinitiator preferably includes an alpha-cleavage (unimolecular decomposition process) photoinitiator or a hydrogen abstraction photosensitizer-tertiary amine synergist operable to absorb light at about 250 nm to about 420 nm or about 300 nm to about 385 nm to generate free radicals.

[0046] Examples of alpha-cleavage photoinitiators are Irgacure 184 (CAS 947-19-3), Irgacure 369 (CAS 119313-12-1), and Irgacure 819 (CAS 162881-26-7) or Omnirad 819. An example of a photosensitizer-amine combination is Darocur BP (CAS 119-61-9) with diethylaminoethyl methacrylate.

[0047] Additionally, in some cases, suitable photoinitiators include benzoins, including benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether, benzoin isopropylphenyl ether, and benzoin acetate; acetophenones, including acetophenone, 2,2-dimethoxyacetophenone, and 1,1-dichloroacetophenone; benzil; benzil ketals, such as benzil dimethyl ketal and benzil diethyl ketal; anthraquinones, such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, and 2-amylanthraquinone; triphenylanthraquinone; benzoylphosphine oxides, for example, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (lucirin TPO); benzophenones such as benzophenone and 4,4'-bis(N,N'-dimethylamino)benzophenone; thioxanthones and xanthones; acridine derivatives, phenazine derivatives, quinoxaline derivatives or 1-phenyl-1,2-propanedione, 2-O-benzoyloxime, 1-aminophenyl ketones; or 1-hydroxyphenyl ketones such as 1-hydroxycyclohexyl phenyl ketone, phenyl 1-hydroxyisopropyl ketone, and 4-isopropylphenyl 1-hydroxyisopropyl ketone.

[0048] Suitable photoinitiators also include photoinitiators operable for use with HeCd laser radiation sources, including acetophenones, 2,2-dialkoxybenzophenones, and 1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone or 2-hydroxyisopropyl phenyl ketone (i.e., 2-hydroxy-2,2-dimethylacetophenone). Additionally, in some cases, suitable photoinitiators include photoinitiators operable for use with Ar laser radiation sources, including benzil ketals, such as benzil dimethyl ketal. In some embodiments, the photoinitiator includes α-hydroxyphenyl ketone, benzil dimethyl ketal, or 2,4,6-trimethylbenzoyldiphenylphosphine oxide, or mixtures thereof.

[0049] Another class of suitable photoinitiators includes, in some cases, ionic dye-counterion compounds that can absorb actinic radiation and generate free radicals for polymerization initiation. In some embodiments, carrier inks containing ionic dye-counterion compounds can polymerize upon exposure to visible light within a tunable wavelength range of about 400 nm to about 700 nm. Ionic dye-counterion compounds and their mode of operation are disclosed in European Patent Application Publication No. 0223587 and U.S. Pat. Nos. 4,751,102; 4,772,530; and 4,772,541.

[0050] The photoinitiator can be present in the carrier inks described herein in any amount consistent with the objectives of the present disclosure. In some embodiments, the photoinitiator is present in the carrier ink in an amount of up to about 5% by weight, up to about 4% by weight, or up to about 3% by weight, based on the total weight of the ink. In some cases, the photoinitiator is present in an amount of about 0.1-5%, 0.1-4%, 0.1-3.5%, 0.1-2%, 0.5-5%, 0.5-4%, 0.5-3.5%, 1-5%, 1-4%, 1-3.5%, 2-5%, or 2-4% by weight, based on the total weight of the carrier ink.

[0051] It should be further understood that the amounts (weight percent) set forth in the immediately preceding paragraph refer to photoinitiators that are non-oligomeric and non-polymeric. That is, the amounts above refer to "monomeric" or "molecular" photoinitiators, which may have, for example, a molecular weight of less than 400. However, it should also be understood that oligomeric or polymeric photoinitiators may be used in the inks and methods described herein. However, in such cases (when oligomeric or polymeric photoinitiators are used), the amounts (weight percent) above should be calculated without taking into account the weight of the oligomeric or polymeric portion or moiety of the oligomeric or polymeric photoinitiator. In other words, to determine the total amount (weight percent) of oligomeric or polymeric photoinitiator present in the ink, the calculation (specifically, the molecular weight) should be based only on the molecular weight of the photoactive portion of the photoinitiator, and not (for purposes of this disclosure) the molecular weight of the remaining portions or repeating units of the oligomeric or polymeric photoinitiator.

[0052] Turning to possible additional components of the carrier inks described herein, the carrier inks described herein can, in some cases, further include one or more photosensitizers. Generally, such sensitizers can be added to the carrier ink to enhance the effectiveness of one or more photoinitiators that may be present. In some cases, the sensitizer includes isopropylthioxanthone (ITX) or 2-chlorothioxanthone (CTX).

[0053] The sensitizer can be present in the carrier ink in any amount consistent with the objectives of the present disclosure. In some embodiments, the sensitizer is present in an amount ranging from about 0.1% to about 2% by weight, or from about 0.5% to about 1% by weight, based on the total weight of the carrier ink. In other cases, however, the carrier ink (or composite ink) described herein excludes such sensitizers.

[0054] Additionally, the carrier inks described herein, in some embodiments, further comprise one or more polymerization inhibitors and / or stabilizers. Polymerization inhibitors may be added to the ink to provide additional thermal stability to the composition. Any polymerization inhibitor not inconsistent with the objectives of the present disclosure may be used. Furthermore, polymerization inhibitors can slow or reduce the rate of polymerization and / or prevent polymerization from occurring for a period of time, or an "induction time," until the polymerization inhibitor is consumed. Furthermore, in some cases, the polymerization inhibitors described herein are "addition-type" inhibitors. The inhibitors described herein may also be "chain-transfer" inhibitors. In some cases, a suitable polymerization inhibitor includes methoxyhydroquinone (MEHQ). In some cases, the inhibitor is commercially available from BASF, Florham Park, New Jersey, under the trade name TINUVIN®.

[0055] The stabilizer, in some embodiments, comprises one or more antioxidants. The stabilizer may include any antioxidant not inconsistent with the objectives of the present disclosure. In some cases, suitable antioxidants include various aryl compounds, including butylated hydroxytoluene (BHT), which may also be used as a polymerization inhibitor in some embodiments described herein. More generally, a single species may serve as both a stabilizer and a polymerization inhibitor. In some cases, multiple inhibitors and / or stabilizers may be used, where different inhibitors and / or stabilizers provide different effects and / or act synergistically.

[0056] The polymerization inhibitor and / or stabilizer can be present in the carrier ink in any amount consistent with the objectives of the present disclosure. In some embodiments, the polymerization inhibitor is present in an amount ranging from about 0.01% to about 2% by weight, or from about 0.05% to about 1% by weight, based on the total weight of the carrier ink. Similarly, in some cases, the stabilizer is present in the carrier ink in an amount ranging from about 0.1% to about 5% by weight, from about 0.5% to about 4% by weight, or from about 1% to about 3% by weight, based on the total weight of the carrier ink. It should also be noted that in some cases, the stabilizers described herein can be added to the composite ink after the carrier or base ink is mixed with the solid powder filler component to form the composite ink.

[0057] Turning to another possible component of the carrier inks described herein, the carrier inks described herein can also include at least one colorant. The colorant of such carrier inks described herein can be a particulate colorant, such as a particulate pigment, or a molecular colorant, such as a molecular dye. Any such particulate or molecular colorant can be used consistent with the objectives of the present disclosure. In some cases, for example, the ink colorant includes an inorganic pigment, such as TiO2 and / or ZnO. In some embodiments, the colorant of the carrier ink can be any of RGB, sRGB, CMY, CMYK, L, and / or IL. * a * b *or colorants for use in Pantone® colorization schemes. Furthermore, in some cases, the particulate colorants described herein have an average particle size of less than about 5 μm or less than about 1 μm. In some cases, the particulate colorants described herein have an average particle size of less than about 500 nm, such as an average particle size of less than about 400 nm, less than about 300 nm, less than about 250 nm, less than about 200 nm, or less than about 150 nm. In some cases, the particulate colorants have an average particle size of about 50-5000 nm, about 50-1000 nm, or about 50-500 nm. The colorants described herein can also include organic species, such as organic small molecule dyes. Such dyes are, in some cases, violet, blue, green, yellow, orange, or red dyes. For example, coumarin, fluorescein, or curcumin may be used in some instances.

[0058] The colorant can be present in the carrier ink described herein in any amount consistent with the objectives of the present disclosure. In some cases, the colorant is present in the carrier ink in an amount of up to about 2% by weight, or in an amount of about 0.005-2%, 0.01-2%, 0.01-1.5%, 0.01-1%, 0.01-0.5%, 0.1-2%, 0.1-1%, 0.1-0.5%, or 0.5-1.5% by weight, based on the total weight of the carrier ink. It should also be noted that in some instances, the colorant is not considered part of the carrier ink, but can be added to the composite ink described herein after the carrier ink and solid powder filler are mixed to form the composite ink. The same is true for some other optional components of the carrier ink described herein.

[0059] In some embodiments, the carrier inks described herein may contain one or more viscosity modifiers. Non-limiting examples of viscosity modifiers include saturated fatty acids or combinations of saturated fatty acids, or oils such as vegetable oils. The carrier inks described herein may contain up to 5% by weight, up to 3% by weight, up to 1% by weight, up to 0.5% by weight, or up to 0.1% by weight of the viscosity modifier, based on the total weight of the carrier ink.

[0060] Additionally, in some embodiments, the carrier ink of the composite ink described herein has a shear viscosity at 30°C of 200 cps or less, 150 cps or less, 100 cps or less, or 50 cps or less, based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 2.

[0061] The carrier ink components of the composite inks described herein can be present in the composite ink in any amount consistent with the technical objectives of the present disclosure. In some cases, the carrier ink is present in an amount of 10 to 80 wt. %, based on the total weight of the composite ink. In some preferred embodiments, the carrier ink is present in an amount of 25 to 55 wt. % or 30 to 45 wt. %, based on the total weight of the composite ink.

[0062] The composite inks described herein also include a solid powder filler dispersed in the carrier ink of the composite ink. Any solid powder filler not inconsistent with the objectives of the present disclosure can be used. Such fillers may generally be non-curing, meaning that the filler does not chemically participate as a reactant in the polymerization reaction used to form the polymer network during additive manufacturing. Such fillers can also be used to impart one or more desirable properties (e.g., color, mechanical strength, or electrical conductivity) to the ink. Non-limiting examples of fillers include inorganic fillers such as ceramic, metal, or other particles, and organic fillers such as discrete organic polymer particles. In some cases, the solid powder filler includes or is formed from zirconia (ZrO), yttria (YO), magnesia (MgO), or another oxide.

[0063] In some preferred embodiments, the solid powder filler comprises or is formed from alumina (Al2O3) or silica (SiO2). In some particularly preferred embodiments, the solid powder filler comprises SiO2 powder. Any SiO2 powder not inconsistent with the technical objectives of the present disclosure can be used. In some cases, for example, the solid powder filler comprises amorphous SiO2. Furthermore, in some embodiments, the solid powder filler comprises or is formed from a combination of two or more oxides, including two or more of the specific oxides listed above. For example, in some instances, the solid powder filler comprises or is formed from: a combination of alumina and silica, such as an aluminosilicate; a combination of zirconia and yttria, such as yttria-stabilized zirconia (YSZ); or a combination of alumina, zirconia, and magnesia, such as alumina doped with zirconia and magnesia. Other combinations are also possible.

[0064] Additionally, the solid powder filler can have a variety of sizes and / or shapes. In some preferred embodiments, the solid powder filler of the composite ink described herein has an average or median particle size (D50) of 0.1 μm to 5 μm (or greater than 0.1 μm up to 5 μm). The average or median particle size (D50) can be measured by any method consistent with the objectives of the present disclosure. In particular, the particle size can be measured using laser diffraction, for example, using a HORIBA laser particle size analyzer. Dynamic image analysis can also be used in accordance with ISO 13322-2. More specifically, size analysis can be performed using a HORIBA LA-960 particle size analyzer, which can be equipped with an LY-9610 or LA-9610 dynamic imaging accessory. In some cases, the solid powder filler has an average or median particle size (D50) of 0.1 μm to 2 μm or 0.1 μm to 1 μm. In some particularly preferred embodiments, the solid powder filler has a mean or median particle size (D50) of 0.1 μm to 0.5 μm. Furthermore, in some cases, the solid powder filler component of the composite inks described herein is free of, or substantially free of, very small or nano-sized particles. For example, in some preferred embodiments, the composite ink is free of, or substantially free of, solid powder fillers having a particle size less than 100 nm (e.g., less than 1 wt. %, less than 0.5 wt. %, less than 0.1 wt. %, or less than 0.01 wt. % SiO2 having a particle size less than 100 nm, where the weight percentages are based on the total weight of the composite ink). In some examples, the solid powder filler of the composite inks described herein has a particle size distribution ranging from 0.1 μm to 10 μm or 0.1 μm to 5 μm, with at least 98 wt. %, at least 99 wt. %, or at least 99.9 wt. % of the solid powder filler particles having a size within this range. Furthermore, in some embodiments, the particle size distribution is unimodal and Gaussian, as opposed to bimodal or other multimodal or non-Gaussian. It should be understood that the above-mentioned sizes can refer to average sizes in three dimensions (e.g., corresponding to equivalent spherical diameters).

[0065] Further, in some cases, the solid powder filler has a uniform size and / or shape. The particles of the solid powder filler can also have a smooth surface texture. In some embodiments, for example, the solid powder filler has an average particle aspect ratio of 1 to 1.1. As will be understood by one of ordinary skill in the art, the aspect ratio of a population of particles (e.g., a population of solid powder filler particles described herein) can be measured by examination of an image of the particles, such as a scanning electron microscope (SEM), transmission electron microscope (TEM), or other microscopic image. Furthermore, in some examples, the solid powder filler is free of or substantially free of irregularly shaped particles (e.g., less than 1%, less than 0.5%, less than 0.1%, or less than 0.01% by weight of particles having an irregular shape or a shape different from that of the rest of the solid powder filler particles, where the weight percentage is based on the total weight of the composite ink). For purposes of reference herein, irregularly shaped particles can be non-spherical or non-spheroidal, or dendritic, or elongated, with an aspect ratio greater than 3.

[0066] Additionally, in some embodiments described herein, the solid powder fillers described herein have a relatively low total surface area, even when the powder's average or median particle size is smaller than other powders with higher total surface areas. Without intending to be bound by theory, it is believed that the exclusion or substantial exclusion of very small particles can provide one or more advantages to the composite powders described herein. In some cases, the solid powder filler component of the composite inks described herein exhibits a surface area of ​​30 mPa or less according to multi-point or single-point BET measurements based on the adsorption of dinitrogen (N2) gas. 2 / g or less, 20m 2 / g or less than 10m 2 In some examples, the solid powder filler component of the composite inks described herein has an average Brunauer-Emmett-Teller (BET) specific surface area of ​​less than 3-30 m / g. 2 / g, 3-20m 2 / g, or 3 to 15 m 2Further, in some particularly preferred embodiments, the solid powder filler has an average particle size of 0.1 μm to 1 μm or 0.1 to 5 μm, as measured as described herein, and an average BET specific surface area of ​​30 μm to 100 μm. 2 / g or less, 20m 2 / g or less than 10m 2 / g or less, or 3 to 30m 2 In some instances, the solid powder filler also has a mean or median particle size (D50) of about 0.3 μm to 0.7 μm and an average BET specific surface area of ​​about 3 μm. 2 / g~15m 2 / g。 Table 1 below shows some non-limiting exemplary combinations of average particle size and BET specific surface area of ​​some exemplary embodiments (e.g., amorphous silica particles) described herein. [Table 1]

[0067] Additionally, in some cases, the particles of the solid powder filler components described herein are functionalized. For example, in some instances, the solid powder filler has a functionalized outer surface. Various functionalizations can be included in the solid powder fillers described herein. Generally, the functionalizations described herein impart or provide chemical functional groups to the surface of the solid powder filler particles that are different from the "native" or functional groups naturally present on the surface of the particles based on their primary chemical composition (e.g., the "functionalization" provides functional groups that are different from the functional groups (such as -OH groups) that may be present on the surface of SiO or AlO particles). In some preferred embodiments, the outer surface of the solid powder filler is functionalized with (meth)acrylate moieties. In some cases, the outer surface of the solid powder filler is functionalized with phenyl, vinyl, or isocyanate moieties. Other functional groups may also be used.

[0068] Any amount or degree of surface functionalization consistent with the technical objectives of the present disclosure can be used. Furthermore, the amount or degree of surface functionalization can be described as a weight percent based on the total filler weight or as moles per unit area of ​​the filler. For example, in some cases, the solid powder fillers described herein can be functionalized with up to 5% by weight of surface functional group species, e.g., 1-2% by weight, based on the total weight of the filler. In some examples, by way of further example, 0.1-5%, 0.1-3%, 0.1-1%, 0.5-5%, 0.5-3%, 1-5%, 1-3%, or 1-2% by weight of silane (meth)acrylate is used to provide (meth)acrylate functionalization on the surface of the solid powder filler, where the weight percent of silane (meth)acrylate (the surface functional group species in this example) is based on the total weight of the filler as the denominator. That is, the weight percent is calculated based on the weight of the silane (meth)acrylate divided by the total weight of the filler and multiplied by 100% to obtain the weight percent. Further, in some embodiments, the amount of surface functional groups is 1 to 100, 1 to 50, 1 to 30, 1 to 20, 1 to 15, or 1 to 10 micromoles of functional groups per square meter of solid powder filler (µmol / m 2 ) i.e. (using (meth)acrylate surface functionalization as an example), the surface area of ​​a solid powder filler is 1 m 2 There may be 1 to 100, 1 to 50, 1 to 30, 1 to 20, 1 to 15, or 1 to 10 micromoles of (meth)acrylate functional groups per ... 2 is.

[0069] The solid powder filler component of the composite ink described herein can be present in the composite ink in any amount consistent with the technical objectives of the present disclosure. In some cases, the solid powder filler is present in an amount of 20 to 85 wt. %, based on the total weight of the composite ink. In some implementations, the solid powder filler is present in an amount of 45 to 70 wt. % or 55 to 65 wt. %, based on the total weight of the composite ink. Furthermore, in some embodiments, the solid powder filler is present in an amount of 10 to 75 volume percent (v. %), based on the total volume of the composite ink. In some implementations, the solid powder filler is present in an amount of 25 to 55 v. % or 38 to 48 v. % based on the total volume of the composite ink.

[0070] The composite inks described herein may optionally include one or more additional components in addition to the carrier ink (including the various components of the carrier ink as described herein) and in addition to the solid powder filler. In some embodiments, for example, the composite ink further includes a dispersant. The dispersant may be, in particular, a dispersant for solid powder filler particles and aid in the dispersion of the solid powder filler within the carrier ink. Any dispersant not inconsistent with the technical objectives of the present disclosure may be used. In some embodiments, the dispersants described herein include a first functional group that has an affinity for or bonds to the surface of the solid powder filler (e.g., silica particles) described herein, and a separate and independent second functional group that has an affinity for or bonds to species in the carrier ink or interacts with the carrier ink as a whole in a manner that promotes dispersion of the solid powder filler within the carrier ink, as opposed to agglomeration or precipitation of the solid powder filler particles. In some cases, the dispersant has one or more siloxane groups (first functional groups) and one or more hydrophobic "tails" (e.g., aromatic or aliphatic hydrocarbyl moieties having 4 to 4,000 carbon atoms). In other examples, the dispersant has one or more acidic moieties, such as one or more carboxylic acid (—COOH) moieties or other Bronsted-Lowry or Lewis acid functional groups (as the first functional group). Such dispersants may be particularly useful for use with solid filler powders having basic moieties or functional groups on their surface, such as hydroxyl (—OH) moieties, amine (—NH) moieties, or other Bronsted-Lowry or Lewis base functional groups. Similarly, in other cases, the dispersant may have one or more basic moieties or functional groups as the first functional group, which, in some embodiments, may be particularly useful for use with solid powder filler particles having acidic moieties or functional groups on their surface. More generally, in some cases, the dispersant in a particular example can be selected based on whether it contains chemical moieties or functional groups that react with, have affinity for, or otherwise bond to or associate with chemical moieties or functional groups on the surface of the solid powder filler particles of the composite ink.Non-limiting examples of dispersants include Lubrizol Solsperse X300, 39000, 41000, 71000, 79000, and 85000; and BYK Disperbyk 111 and Disperbyk 180. Other dispersants may also be used.

[0071] The dispersant of the composite ink, when present, can be present in any amount consistent with the technical objectives of the present disclosure. In some preferred embodiments, the dispersant, when present, is present in an amount of 0.2 to 5% by weight relative to the amount of solid powder filler.

[0072] The composite inks described herein may, in some cases, further include an antifoaming or degassing agent, and such species (if present) may be present in an amount of up to about 5% by weight, based on the total weight of the composite ink.

[0073] The composite inks described herein can also exhibit various desirable properties in the cured state, in addition to those described above. As used throughout this disclosure, ink in a "cured" state includes inks containing curable materials or polymerizable components that are at least partially cured, i.e., at least partially polymerized and / or crosslinked. For example, in some cases, the cured ink is at least about 70% polymerized or crosslinked, or at least about 80% polymerized or crosslinked. In some embodiments, the cured ink is at least about 85%, at least about 90%, at least about 95%, at least about 98%, or at least 99% polymerized or crosslinked. In some examples, the cured ink is about 80% to about 99% polymerized or crosslinked. As noted above, the degree of polymerization or crosslinking of the ink can be determined using any protocol or method consistent with the technical objectives of the present disclosure, for example, by measuring the percentage of monomer incorporated into the polymer network (e.g., based on the molecular weight of the polymer compared to the molecular weight of the monomer, or based on the total polymer mass compared to the theoretical maximum of the total polymer mass) or by measuring the amount of unincorporated monomer. When multiple methods are used to determine the degree of polymerization or crosslinking, the results of these methods can be averaged to arrive at the percentages described herein. It should be further understood that the degree of polymerization or crosslinking described herein is different from the "degree of polymerization," which is defined as the number of repeat units in a polymer molecule.

[0074] In some cases, the composite inks described herein (or 3D articles printed therefrom) in the cured state can have one or more advantages compared to some other inks or composite inks, particularly (meth)acrylate-containing inks. For example, in some examples, the composite inks described herein (or articles formed therefrom) in the cured state have a high flexural and / or elastic modulus, e.g., a flexural modulus of 8500 to 11,500 MPa as measured according to ASTM D790, and / or a modulus of 9000 to 12,000 MPa as measured according to ASTM D638 Type IV. Furthermore, in some embodiments, the composite inks described herein, when cured, have a high tensile strength and / or flexural strength, e.g., a tensile strength of 50 to 90 MPa or 70 to 90 MPa as measured according to ASTM D638 Type IV, and / or a flexural strength of 70 to 150 MPa or 90 to 150 MPa as measured according to ASTM D790. In some examples, the composite inks described herein, when cured, have an elongation at break of 0.7-2% or 0.7-1.8%, as measured according to ASTM D638 Type IV. Furthermore, in some cases, the composite inks described herein, when cured, may exhibit multiple properties described in this disclosure. For example, in some examples, the composite inks described herein, in the cured state, have at least two, at least three, or at least four of the following: (1) a flexural modulus within the ranges set forth above, (2) a modulus within the ranges set forth above, (3) a tensile strength within the ranges set forth above, (4) a flexural strength within the ranges set forth above, and (5) an elongation at break within the ranges set forth above.

[0075] The inks and composite inks described herein can be manufactured by any method consistent with the objectives of the present disclosure. In some embodiments, for example, methods for preparing the inks described herein include mixing the ink components, melting the mixture, and filtering the molten mixture. In some cases, the melting step is performed at a temperature of about 75°C or a temperature in the range of about 75°C to about 85°C. In some embodiments, the inks described herein are manufactured by placing all of the ink components into a reaction vessel and heating the resulting mixture to a temperature in the range of about 75°C to about 85°C while stirring. Heating and stirring are continued until the mixture reaches a substantially homogenized molten state. Generally, the molten mixture can be filtered while in a fluid state to remove any large, undesirable particles (it is understood that solid powder filler particles, if present, are not removed by the filtering step). The filtered mixture can then be cooled to ambient temperature and stored until ready for use in a 3D printing system. It is also possible to prepare an ink described herein (such as a carrier ink or a base ink) as described above, and then, after filtration, add solid powder filler particles to the carrier or base ink while stirring, mixing, rolling, or agitating to disperse the solid powder filler particles in the carrier or base ink without further filtration following this mixing step.

[0076] II. Methods of Forming 3D Articles In another aspect, methods of forming or "printing" 3D articles or objects by additive manufacturing are described herein. The methods of forming 3D articles or objects described herein can include forming a 3D article from multiple layers of the inks described herein in a layer-by-layer manner (e.g., MJP or SLA printing methods). For example, in some examples, an MJP method of printing a 3D article includes selectively depositing a layer of a composite ink described herein in a fluid state onto a substrate, such as a build pad of a 3D printing system. The method can further include curing (e.g., photocuring) the ink. Furthermore, the curing can include polymerizing one or more polymerizable moieties or functional groups of one or more components of the ink. In some cases, a deposited layer of ink is cured before depositing another or adjacent layer of ink. Furthermore, in some embodiments, curing one or more layers of deposited ink is performed by exposing the one or more layers to electromagnetic radiation, such as ultraviolet (UV) light, visible light, or infrared light, as described above. Additionally, in some embodiments, such methods further include supporting at least one of the layers of the ink with a support material, before or after curing. As further described below, any support material not inconsistent with the objectives of the present disclosure can be used.

[0077] Alternatively, a method of printing a 3D article includes: holding ink in a fluid state (e.g., the composite ink described above in Section I) in a container; selectively applying energy to the ink in the container to solidify at least a portion of a first fluid layer of the ink, thereby forming a first solidified layer that defines a first cross-section of the article; raising or lowering the first solidified layer to provide a second fluid layer of the ink on a surface of the fluid ink in the container; and selectively applying energy to the ink in the container to solidify at least a portion of the second fluid layer of the ink, thereby forming a second solidified layer that defines a second cross-section of the article, wherein the first cross-section and the second cross-section are joined to each other in the z-direction. Further, in some such embodiments, selectively applying energy to the ink in the container includes photocuring the ink. Additionally, such methods can, in some cases, be practiced using only or primarily photocuring and no thermal or cationic curing of the polymerizable moieties or curable materials described herein (e.g., using less than 10%, less than 5%, or less than 1% thermal or cationic curing, percentages based on the mole percent of the cured moieties as described above).

[0078] Additionally, in some embodiments of the methods described herein, one or more layers of the inks described herein have a thickness of about 10 μm to about 100 μm, about 10 μm to about 80 μm, about 10 μm to about 50 μm, about 20 μm to about 100 μm, about 20 μm to about 80 μm, or about 20 μm to about 40 μm. Other thicknesses are possible.

[0079] Methods of forming 3D articles by additive manufacturing can also include forming objects in ways other than a layer-by-layer manner.

[0080] Additionally, any of the inks described above in Section I may be used in the methods described herein. For example, in some cases, the ink used in the methods described herein comprises a composite ink comprising 30-45% by weight of a carrier ink and 45-70% by weight of a solid powder filler dispersed in the carrier ink, based on the total weight of the composite ink.

[0081] Further details regarding various methods, including "material deposition" methods (such as MJP) or "vat polymerization" methods (such as SLA), are provided below.

[0082] A. Material deposition method In material deposition methods, one or more layers of the inks described herein are selectively deposited on a substrate and cured. Curing of the ink can occur after selective deposition of one, each, multiple, or all layers of the ink.

[0083] In some examples, the inks described herein are selectively deposited in a fluid state onto a substrate, such as a build pad of a 3D printing system. Selective deposition may include, for example, depositing the ink according to preselected CAD parameters. For example, in some embodiments, a CAD file drawing corresponding to the desired 3D article to be printed is generated and sliced ​​into a sufficient number of horizontal slices. The ink is then selectively deposited layer-by-layer according to the horizontal slices of the CAD file drawing (or other digital representation of the desired 3D article) to print the desired 3D article. A "sufficient" number of horizontal slices is the number necessary for successful printing of the desired 3D article, for example, to accurately and precisely manufacture the desired 3D article.

[0084] Furthermore, in some embodiments, a preselected amount of the ink described herein is heated to an appropriate temperature and ejected through one or more printheads of a suitable inkjet printer to form a layer on a print pad in a print chamber. In some cases, each layer of ink is deposited according to preselected CAD parameters (or other digital parameters corresponding to the desired article). A printhead suitable for depositing the ink, in some embodiments, is a piezoelectric printhead. Additional printheads suitable for depositing the inks and support materials described herein are commercially available from various inkjet printing equipment manufacturers. For example, in some cases, printheads from Xerox, Hewlett Packard, or Ricoh can be used.

[0085] Additionally, in some embodiments, the inks described herein remain substantially fluid upon deposition. Alternatively, in other examples, the inks exhibit a phase change upon deposition and / or solidify upon deposition. Furthermore, in some cases, the temperature of the printing environment can be controlled so that jetted ink droplets solidify upon contact with the receiving surface. In other embodiments, the jetted ink droplets do not solidify upon contact with the receiving surface but remain substantially fluid. Furthermore, in some cases, after each layer is deposited and before the deposition of the next layer, the deposited material is planarized and cured with electromagnetic (e.g., UV, visible, or infrared) radiation. Optionally, multiple layers can be deposited before planarization and curing, or multiple layers can be deposited and cured, followed by deposition of one or more layers and then planarization without curing. Planarization compensates for the thickness of one or more layers before curing the material by flattening the jetted material to remove excess material and form a uniformly smooth, exposed, or flat, upward-facing surface on the printer's support platform. In some embodiments, the planarization is performed using a wiper device, such as a roller, which may counter-rotate in one or more printing directions but not in one or more other printing directions. In some cases, the wiper device comprises a roller and a wiper that removes excess material from the roller. Additionally, in some cases, the wiper device is heated. Note that in some embodiments, it is desirable that the viscosity of the jetted ink described herein before curing is sufficient to retain its shape and not experience excessive viscous drag from the planarization device.

[0086] Furthermore, if used, the support material can be deposited in a manner consistent with the methods described above for the ink. The support material can be deposited according to preselected CAD parameters (or other digital parameters), for example, so that the support material is adjacent to or continuous with one or more layers of ink. In some embodiments, jetted droplets of the support material solidify or freeze upon contact with the receiving surface. In some cases, the deposited support material is also subjected to planarization, curing, or planarization and curing. Any support material not inconsistent with the objectives of the present disclosure can be used.

[0087] The layer-by-layer deposition of ink and support material can be repeated until the 3D article is formed. In some embodiments, the method of printing a 3D article further comprises removing the support material from the ink.

[0088] Curing of the ink can occur after selectively depositing one layer of ink, each layer of ink, multiple layers of ink, or all layers of ink needed to print the desired 3D article. In some embodiments, partial curing of the deposited ink occurs after selectively depositing one layer of ink, each layer of ink, multiple layers of ink, or all layers of ink needed to print the desired 3D article. For reference purposes herein, a "partially cured" ink is one that can undergo further curing. For example, a partially cured ink is up to about 30% polymerized or crosslinked, or up to about 50% polymerized or crosslinked. In some embodiments, a partially cured ink is up to about 60%, up to about 70%, up to about 80%, up to about 90%, or up to about 95% polymerized or crosslinked.

[0089] Partial curing of the deposited ink can include irradiating the ink with an electromagnetic radiation source or photocuring the ink (including with the curing radiation described above). Any electromagnetic radiation source consistent with the objectives of the present disclosure can be used, for example, an electromagnetic radiation source that emits UV, visible, or infrared light. For example, in some embodiments, the electromagnetic radiation source can be one that emits light having a wavelength of about 300 nm to about 900 nm, such as a Xe arc lamp.

[0090] Further, in some embodiments, post-curing is performed after partial curing. For example, in some cases, post-curing is performed after selectively depositing all layers of ink necessary to form the desired 3D article, after partially curing all layers of ink, or after both of the aforementioned steps are performed. Further, in some embodiments, post-curing includes photocuring. Again, any electromagnetic radiation source consistent with the objectives of the present disclosure can be used for the post-curing step described herein. For example, in some embodiments, the electromagnetic radiation source can be a light source having higher energy, lower energy, or the same energy as the electromagnetic radiation source used for partial curing. If the electromagnetic radiation source used for post-curing has higher energy (i.e., shorter wavelength) than that used for partial curing, a Xe arc lamp can be used for partial curing and a Hg lamp can be used for post-curing.

[0091] Furthermore, after post-curing, in some cases, the deposited ink layer is at least about 80% polymerized or crosslinked, or at least about 85% polymerized or crosslinked. In some embodiments, the deposited ink layer is at least about 90%, at least about 95%, at least about 98%, or at least about 99% polymerized or crosslinked. In some examples, the deposited ink layer is about 80-100%, about 80-99%, about 80-95%, about 85-100%, about 85-99%, about 85-95%, about 90-100%, or about 90-99% polymerized or crosslinked.

[0092] B. Vat polymerization method It is also possible to form 3D articles from the inks described herein using vat polymerization methods, such as SLA. Thus, in some cases, a method for printing a 3D article described herein includes holding the ink described herein in a fluid state in a container and selectively applying energy (e.g., curing radiation) to the ink in the container to solidify at least a portion of the fluid layer of ink, thereby forming a solidified layer that defines a cross-section of the 3D article. Furthermore, the method described herein can further include raising or lowering the solidified layer of ink to provide a new or second fluid layer of unsolidified ink on the surface of the fluid ink in the container, and then selectively applying energy (e.g., curing radiation) to the ink in the container again to solidify at least a portion of the new or second fluid layer of ink, forming a second solidified layer that defines a second cross-section of the 3D article. Furthermore, the first and second cross-sections of the 3D article can be bonded or adhered to each other in the z-direction (or a build direction corresponding to the above-mentioned direction of raising or lowering) by applying energy to solidify the ink. Additionally, in some examples, the electromagnetic radiation has an average wavelength of 300 to 900 nm, and in other embodiments, the electromagnetic radiation has an average wavelength of less than 300 nm. In some cases, the curing radiation is provided by a computer-controlled laser beam. Furthermore, in some cases, raising or lowering the solidified layer of ink is accomplished using an elevator platform positioned within the reservoir of fluid ink. The methods described herein may also include a step of planarizing the new layer of fluid ink provided by raising or lowering the elevator platform. Such planarization may, in some cases, be accomplished by a wiper or roller.

[0093] It should be further understood that the foregoing process can be repeated as many times as desired to provide a 3D article. For example, in some cases, the process can be repeated "n" times, where n can be up to about 100,000, up to about 50,000, up to about 100,000, up to about 5000, up to about 1000, or up to about 500. Thus, in some embodiments, a method of printing a 3D article described herein can include selectively applying energy (e.g., curing radiation) to the ink in the container to solidify at least a portion of the nth fluid layer of ink, thereby forming an nth solidified layer that defines the nth cross-section of the 3D article; raising or lowering the nth solidified layer of ink to provide an (n+1)th layer of unsolidified ink on a surface of the fluid ink in the container; selectively applying energy to the (n+1)th layer of ink in the container to solidify at least a portion of the (n+1)th layer of ink to form an (n+1)th solidified layer that defines the (n+1)th cross-section of the 3D article; raising or lowering the (n+1)th solidified layer of ink to provide an (n+2)th layer of unsolidified ink on the surface of the fluid ink in the container; and continuing to repeat the foregoing steps to form the 3D article. It should further be understood that one or more steps of the methods described herein, such as selectively applying energy (e.g., curing radiation) to a layer of ink, can be performed according to an image of the 3D article in computer-readable or digital form. General methods of 3D printing using stereolithography are further described in, among other places, U.S. Patent Nos. 5,904,889 and 6,558,606.

[0094] By implementing the printing process described above, 3D articles printed from the inks described herein can be provided with high feature resolution. For reference purposes herein, the "feature resolution" of an article can refer to the smallest controllable physical feature size of the article. The feature resolution of an article can be expressed in terms of distance units, such as microns (μm), or in terms of dots per inch (dpi). As will be understood by those skilled in the art, higher feature resolution corresponds to higher dpi values ​​but lower distance values ​​in μm. In some cases, articles formed by depositing or solidifying the inks described herein can have a feature resolution of about 500 μm or less, about 200 μm or less, about 100 μm or less, or about 50 μm or less, including those at elevated temperatures. In some embodiments, the articles have a feature resolution of about 50 μm to about 500 μm, about 50 μm to about 200 μm, about 50 μm to about 100 μm, or about 100 μm to about 200 μm. Similarly, in some examples, the articles described herein have a feature resolution of at least about 100 dpi, at least about 200 dpi, at least about 250 dpi, at least about 400 dpi, or at least about 500 dpi. In some cases, the feature resolution of the articles is from about 100 dpi to about 600 dpi, from about 100 dpi to about 250 dpi, or from about 200 dpi to about 600 dpi.

[0095] In vat polymerization processes such as those described above, the ink may be partially cured as described in Section IIA above. For example, in some embodiments, selectively applying energy to the ink in the reservoir to solidify at least a portion of the fluid layer of the ink may include partially curing at least a portion of the fluid layer of the ink. In other embodiments, partially curing at least a portion of the fluid layer of the ink may occur after a first layer of ink is applied and solidified, before or after a second layer of ink is applied or solidified, or before or after one, more, or all subsequent layers of ink are applied or solidified.

[0096] Additionally, in some embodiments of the vat polymerization methods described herein, post-curing as described in Section IIA above may occur after partial curing or after the desired 3D article has been formed, which may be, for example, an article corresponding to a design in a CAD file.

[0097] III. Printed 3D Articles In another aspect, printed 3D articles are described herein. In some embodiments, the printed 3D articles are formed from the inks described herein. Any of the inks described above in Section I can be used. For example, in some cases, the ink comprises a composite ink including 30-45% by weight of a carrier ink and 45-70% by weight of a solid powder filler dispersed in the carrier ink, based on the total weight of the composite ink. Furthermore, in some cases, the printed 3D articles described herein are formed primarily from a poly(meth)acrylate polymer network that includes or encapsulates solid powder filler particles.

[0098] Some embodiments of inks for 3D printing are further described in the following non-limiting examples. [Example]

[0099] Example 1 HALT test method The HALT score of an ink is measured as follows. Generally, highly accelerated life testing (HALT) is a method for testing a liquid or slurry for changes in its physical properties over time and under different conditions. In this case, the conditions tested include time and temperature, and the property tested is sedimentation. To perform HALT, a known mass (15 g) of ink in its liquid (uncured) state is placed in a container or oven at room temperature (22°C). The oven is set to a specific temperature (e.g., 50°C or 65°C). The container is a 20 mL scintillation glass vial pre-loaded with 6.5 g ± 0.1 g stainless steel balls (3 mm diameter), enough balls to cover the bottom of the vial in one layer. The test vial (containing the test ink placed on the layer of stainless steel balls) is left in an upright position at a specific temperature (e.g., 22°C, 50°C, or 65°C). Sedimentation is measured at specific time points, and the total test period is typically 8 weeks or longer. At each time point, sedimentation is measured as follows: After completion of each sedimentation test, the test vial is returned to its original upright position.

[0100] At each time point where sedimentation is measured, the sedimentation of the stainless steel ball is scored by measuring the time it takes for the stainless steel ball (specific gravity 7.99-8.00 g / cc) to fall a predetermined distance within the vial after the vial is turned on its side (90 degrees from the upright position). Figure 1 shows a 20 mL vial in an upright position containing a stainless steel ball of fixed mass (6.5 ± 0.1 g) at the bottom. As shown in Figure 2, a stopwatch is started by a human operator when the vial is turned on its side and gravity begins to act on the stainless steel ball. The fall of the stainless steel ball within the vial is visually observed by the human operator. When the stainless steel ball falls a distance of one-third the diameter of the vial (8.5 mm), the human operator stops the timer and records the elapsed time to the nearest 1-second interval.

[0101] A HALT score is assigned based on the elapsed time. There are four possible scores: 3, 2, 1, and 0. The highest or best score is 3. A score of 3 means the ball fell the fastest within 5 seconds or less of the elapsed time, as shown in Table 2 below and Figure 3. [Table 2]

[0102] A HALT score of 2 is associated with a time between 6 and 15 seconds. A HALT score of 1 is assigned to an elapsed time between 16 and 30 seconds, and a HALT score of 0 is assigned to any elapsed time greater than 30 seconds. As seen in Figure 4, a test sample showing little or no movement of the stainless steel ball after 30 seconds is an indication of severe settlement and the end of the overall HALT rating for that sample (regardless of the specific measurement time point at which this observation is made).

[0103] A HALT score is assigned to each time point at which measurements are taken. As further described herein, a HALT score of at least 2 over a period of at least 14 days (or 2 weeks) is considered an acceptable result, with a HALT score of 3 being preferred in some embodiments.

[0104] Example 2 Carrier ink viscosity test method The viscosity of the carrier or base ink described herein (without solid powder fillers) is measured using a Brookfield Ametek DVE-LV viscometer, model DVEELVTJO, equipped with a Brookfield Ametek low-volume sample adapter. Environmental conditions for testing are controlled by the water jacket of the low-volume sample adapter, which is connected to a Brookfield TC-650 Refrigerated Circulating Bath. The temperature of the test sample is maintained at 30°C ± 0.5°C. The sample is maintained at approximately 21°C (laboratory conditions) for at least one day prior to viscosity testing. The Brookfield measurement tool is as follows: size SC4-13R chamber (diameter 19.05 mm) and size #21 spindle (spindle L, 31.24 mm; spindle D, 16.77 mm; spindle effective L, 35.15 mm). The test ink is poured into a 10 mL disposable syringe instead of being drawn into the syringe to prevent pre-shearing and bubble formation. After adjusting the sample volume to 7.2 mL, slowly dose the sample inside the chamber to minimize foam / bubble formation. Slowly insert the spindle into the resin, raise it 1-3 mm, and hold for 5-15 seconds, allowing the test ink to flow under the spindle. Attach the chamber and spindle to the viscometer and begin the test. The rotation speed (revolutions per minute, RPM) is set to its minimum value, and the start time of the experiment is recorded. If the % full scale range (FSR) of the torque measurement is less than 75%, the rotation speed (RPM) is slowly increased to reach at least 75% full scale range (FSR) and left for a steady-state measurement. The final viscosity value is reported at 15 minutes of measurement in centipoise (cP).

[0105] Example 3 Composite ink fluidity test method The flow properties of the composite liquids or inks described herein (containing solid powder fillers) were measured using an ARES-G2 rheometer from TA Instruments. The method was developed based on ASTM D4440-15 and adapted for slurry liquids. A parallel-plate (circular disk) geometry was utilized, with a 40 mm (diameter) stainless steel bottom plate and a top plate (circular disk). The gap size (sample thickness) was maintained at 1 ± 0.05 mm, and the test temperature was 30.0 ± 0.5 °C. Two primary test methods were utilized to evaluate the flow behavior of the samples: (1) steady torsional shear and (2) small amplitude oscillatory shear (SAOS) method. Steady torsional shear measurements were performed in a stress-growth test setup on the rheometer, where five different shear rate values ​​(0.01, 0.05, 0.1, 0.5, and 1 s-1) were applied to the sample sequentially over fixed time intervals. Steady-state viscosity values ​​for each shear rate were reported, and shear viscosity curves (shear viscosity vs. shear rate) for the samples were obtained. For the small amplitude oscillatory shear (SAOS) method, strain amplitude sweep and dynamic frequency sweep tests were applied. Strain amplitude sweep tests were applied to ensure that the dynamic frequency sweep tests were conducted under linear viscoelastic conditions. Strain values ​​were varied from 0.1% to 100% strain amplitude at a constant angular frequency value of 5 rad / s, and the onset of nonlinear strain amplitude values ​​was observed at strain amplitude values ​​of 1% to 2%. Dynamic frequency sweep tests were applied in the range of 0.1 to 100 rad / s at 1 or 2% strain amplitude values, depending on the onset of nonlinear conditions for the sample. The storage (elastic) modulus (G'), loss (viscous) modulus (G"), and tan delta value (G" / G') were calculated and reported. An exemplary plot of the storage modulus (G', bottom curve) and loss modulus (G", top curve) as a function of angular frequency (rad / s) for a composite ink according to one embodiment described herein is shown in FIG. 5 to aid in overall understanding. Specifically, FIG. 5 corresponds to Composite Ink 2 in Example 5 below.

[0106] Example 4 Carrier ink Inks according to some embodiments described herein were prepared as follows. Specifically, to prepare various carrier inks, the ink components were mixed in a reaction vessel to form a particular carrier or base ink (e.g., as shown for Carrier Inks 1-8 in Table 3). The amounts of various components in Table 3 refer to the mass % of each component of the identified ink, based on the total weight of the ink. For each ink, the appropriate mixture was heated to a predetermined temperature (e.g., 50-70°C) with stirring. Heating and stirring continued until the mixture reached a substantially homogeneous state. Next, in some cases, the mixture was allowed to cool to ambient temperature if a solid powder filler was to be added later. Alternatively, the solid powder filler may be added to the completed carrier ink before it is cooled. Furthermore, as described in Example 5 below, it is also possible to add a solid powder filler component to all of the carrier ink components, so that the heating, stirring, and / or blending process described above is performed in the presence of all components (including both filler and carrier ink components), and the result of the process is a composite ink described herein. In such cases, the composite ink can be cooled to a particular temperature, such as room temperature, if desired, after blending of the components is complete.

[0107] In Table 3, "Mono." refers to the monomeric curable material component; "Oligo." refers to the oligomeric curable material component; "PI" refers to the photoinitiator component; "Stab." refers to the stabilizer component; and "Color." refers to the colorant component. For Carrier Ink 1 in Table 3, the monomeric curable material component included a mixture of monofunctional (meth)acrylate (67.2% by weight) and trifunctional (meth)acrylate (11% by weight). The oligomeric curable material component of Carrier Ink 1 was a polymeric / oligomeric urethane acrylate. The photoinitiator was bisacylphosphine oxide (BAPO), the stabilizer was butylated hydroxytoluene (BHT), and the colorant was curcumin.

[0108] For Carrier Ink 2 in Table 3, the monomeric curable material component included a mixture of monofunctional (meth)acrylate (67.01 wt%) and trifunctional (meth)acrylate (11.04 wt%). The oligomeric curable material component of Carrier Ink 2 was an oligomeric urethane acrylate. The photoinitiator was Omnirad or Irgacure 819, and the stabilizer was BHT.

[0109] For Carrier Ink 3 in Table 3, the monomeric curable material component included a mixture of monofunctional (meth)acrylate (67.06 wt%) and trifunctional (meth)acrylate (11.04 wt%). The oligomeric curable material component of Carrier Ink 3 was an oligomeric urethane acrylate. The photoinitiator was Omnirad or Irgacure 819, and the stabilizer was BHT.

[0110] For Carrier Ink 4 in Table 3, the monomeric curable material component included a mixture of monofunctional (meth)acrylate (69.6 wt%) and trifunctional allylic (11.2 wt%). The oligomeric curable material component of Carrier Ink 4 was oligomeric urethane dimethacrylate. The photoinitiator was Omnirad or Irgacure 819.

[0111] For Carrier Ink 5 in Table 3, the monomeric curable material component included a mixture of monofunctional (meth)acrylate (58.8 wt%) and trifunctional (meth)acrylate (29.4 wt%). The oligomeric curable material component of Carrier Ink 5 was oligomeric urethane dimethacrylate. The photoinitiator was Omnirad or Irgacure 819.

[0112] For Carrier Ink 6 in Table 3, the monomeric curable material component included a mixture of monofunctional (meth)acrylate (39.2 wt%) and trifunctional (meth)acrylate (29.4 wt%). The oligomeric curable material component of Carrier Ink 6 was oligomeric urethane dimethacrylate. The photoinitiator was Omnirad or Irgacure 819.

[0113] For Carrier Ink 7 in Table 3, the monomeric curable material component included a mixture of monofunctional (meth)acrylate (69.6 wt%) and trifunctional (meth)acrylate (11.2 wt%). The oligomeric curable material component of Carrier Ink 7 was oligomeric urethane dimethacrylate. The photoinitiator was Omnirad or Irgacure 819.

[0114] For Carrier Ink 8 in Table 3, the monomeric curable material component included a mixture of monofunctional (meth)acrylate (68.9 wt%) and trifunctional (meth)acrylate (11.1 wt%). The oligomeric curable material component of Carrier Ink 8 was oligomeric urethane dimethacrylate. The photoinitiator was Omnirad or Irgacure 819. [Table 3]

[0115] Example 5 Composite ink Non-limiting examples of composite inks according to some embodiments described herein were prepared as follows. With reference to Table 4, the identified carrier inks were mixed with the identified solid powder fillers to obtain the composite inks. As noted above, this mixing can be performed sequentially or simultaneously. That is, in one option, the carrier ink may be prepared as described in Example 4 above, and then the solid powder filler (and optionally other ingredients) may be subsequently added to the carrier ink with mixing, blending, and / or heating. Furthermore, in such cases, the carrier ink may still be warm or heated when the solid powder filler component (and optionally other ingredients) is added. Alternatively, in another option, the solid powder filler component (and optionally other ingredients) may be mixed with the carrier ink components, and all ingredients may be stirred, blended, mixed, and / or heated together in essentially one step to provide the composite ink.

[0116] The amounts shown in Table 4 refer to mass percent based on the total weight of the composite ink. The "Carrier Ink" column refers to the numbered exemplary carrier ink from Example 4 (e.g., "1" in this column refers to Carrier Ink 1 from Example 4). The "Filler" column in Table 4 refers to the numbered exemplary filler from Table 5 (e.g., "1" in this column refers to Filler 1 from Table 5).

[0117] The remaining components of composite inks 2-6 were colorant (1.2 wt%), dispersant (0.3 wt%), and degassing agent (1%). The remaining components of composite inks 7-11 were colorant (0.2 wt%), dispersant (0.3 wt%), degassing agent (0.3%), and additional monomeric methacrylate (0.5 wt%). The remaining components of composite inks 12-15 were colorant (0.6 wt%), dispersant (1.3 wt%), degassing agent (1%), and stabilizer (0.5 wt%). The remaining components of composite inks 16-20 were defoamer / degassing agent (1 wt%) and stabilizer (0.5 wt%), with varying amounts of dispersant (0 wt%, 0.65 wt%, 1.3 wt%, 2.6 wt%, and 5.2 wt% for composite inks 16-20, respectively).

[0118] In Table 5, the "Material" column refers to the material from which the solid powder filler particles are formed; the "Surface Functional Group" column refers to the functional groups present on the outer surface of the particles due to the surface functionalization described herein; the "Particle Size" column refers to the D50 particle size in microns; and the "Particle Shape" column refers to the particle shape based on SEM analysis. [Table 4] [Table 5]

[0119] As stated above, it should be understood that the composite inks described and claimed herein are not limited to only the precise embodiments of this or any other specific example. Instead, other specific inks can be formulated by one skilled in the art based on the teachings of the present disclosure.

[0120] Example 6 Performance Data Various properties of several composite inks described herein were measured. As shown below, some composite inks exhibited specific structural characteristics that were preferable over those of other composite inks. The composite ink data presented in this example was based on cured articles printed from the inks using a Figure 4® Additive Manufacturing System from 3D Systems, Inc. In Table 6, HALT scores were measured at 22°C, 50°C, and 65°C for 14 days (or longer) as described in Example 1. The mechanical properties in Table 7 were measured according to ASTM D790 and / or D628 Type IV. In Tables 6 and 7, the "Composite Ink" column refers to the specific composite ink number from Example 5 and Table 4. "HALT" in Table 6 refers to the HALT scores at 22°C, 50°C, and 65°C (for composite inks 7, 9, 10, and 11), respectively, or at 22°C, 60°C, and 70°C (for composite inks 16-20), respectively. In Table 7, "FS" refers to flexural strength; "TS" refers to tensile strength; "EOB" refers to elongation at break; "FM" refers to flexural modulus; and "EM" refers to elastic modulus. [Table 6] [Table 7]

[0121] Some additional non-limiting exemplary embodiments are provided further below.

[0122] Embodiment 1. A composite ink for use in a three dimensional printing system, comprising: a carrier ink comprising a curable material; and a solid powder filler dispersed in said carrier ink; Including, the composite ink, in an uncured state, has a highly accelerated life test (HALT) score of at least 2 when tested at 65°C for at least 14 days; and / or The composite ink, in an uncured state, has an average loss factor tanδ of 2 or less over an angular frequency range of 0.5 to 5 rad / s. A composite ink characterized by:

[0123] Embodiment 2. The composite ink of embodiment 1, wherein the composite ink has a HALT score of 3 when tested at 65° C. for at least 14 days.

[0124] Embodiment 3. The composite ink of embodiment 1 or embodiment 2, wherein the composite ink has a shear viscosity of 5000 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3.

[0125] Embodiment 4. The composite ink of embodiment 1 or embodiment 2, wherein the composite ink has a shear viscosity of 3000 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3.

[0126] Embodiment 5. The composite ink of embodiment 1 or embodiment 2, wherein the composite ink has a shear viscosity of 2000 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3.

[0127] Embodiment 6. The composite ink of embodiment 1 or embodiment 2, wherein the composite ink has a shear viscosity of 500 to 1500 cps at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3.

[0128] Embodiment 7. The composite ink of any of the preceding embodiments, wherein the curable material of the carrier ink comprises one or more monomeric curable materials.

[0129]

[0020] Embodiment 8. The composite ink of embodiment 7, wherein the one or more monomeric curable materials are present in the carrier ink in an amount of 15% to 85% by weight, based on the total weight of the carrier ink.

[0130] Embodiment 9. The composite ink of any of the preceding embodiments, wherein the curable material of the carrier ink comprises one or more oligomeric curable materials.

[0131]

[0020] Embodiment 10. The composite ink of embodiment 9, wherein the one or more oligomeric curable materials are present in the carrier ink in an amount of 15% to 85% by weight, based on the total weight of the carrier ink.

[0132]

[0022] Embodiment 11. The composite ink of any of the preceding embodiments, wherein the curable material of the carrier ink comprises a combination of one or more monomeric curable materials and one or more oligomeric curable materials.

[0133] Embodiment 12. The composite ink of any of the preceding embodiments, wherein the curable material of the carrier ink comprises one or more acrylate, methacrylate, or vinyl species.

[0134] Embodiment 13. The composite ink of any of the previous embodiments, wherein the curable material of the carrier ink comprises one or more epoxy species.

[0135] Embodiment 14. The composite ink of any of the preceding embodiments, wherein all or substantially all of the curable materials of the carrier ink are curable by free radical polymerization.

[0136]

[0022] Embodiment 15. The composite ink of any of the preceding embodiments, wherein the carrier ink further comprises a photoinitiator component.

[0137]

[0030] Embodiment 16. The composite ink of embodiment 15, wherein the photoinitiator component is present in the carrier ink in an amount of 5% by weight or less.

[0138]

[0022] Embodiment 17. The composite ink of any of the preceding embodiments, wherein the carrier ink further comprises an inhibitor component.

[0139]

[0030] Embodiment 18. The composite ink of embodiment 17, wherein the inhibitor component is present in the carrier ink in an amount of 1% by weight or less.

[0140] Embodiment 19. The composite ink of any of the previous embodiments, wherein the carrier ink has a shear viscosity of 200 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 2.

[0141] Embodiment 20. The composite ink of any of the previous embodiments, wherein the carrier ink has a shear viscosity of 150 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 2.

[0142] Embodiment 21. The composite ink of any of the previous embodiments, wherein the carrier ink has a shear viscosity of 100 cps or less, or 50 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 2.

[0143] Embodiment 22. The composite ink of any of the preceding embodiments, wherein the solid powder filler comprises SiO powder.

[0144] Embodiment 23. The composite ink of embodiment 22, wherein the solid powder filler comprises amorphous SiO2.

[0145] Embodiment 24. The composite ink of any of the preceding embodiments, wherein the solid powder filler has an average particle size of 0.1 μm to 5 μm.

[0146] Embodiment 25. The composite ink of any of the preceding embodiments, wherein the solid powder filler has an average particle size of 0.1 μm to 2 μm.

[0147] Embodiment 26. The composite ink of any of the preceding embodiments, wherein the solid powder filler has an average particle size of 0.1 μm to 1 μm.

[0148] Embodiment 27. The composite ink of any of the preceding embodiments, wherein the solid powder filler has an average particle size of 0.1 μm to 0.5 μm.

[0149] Embodiment 28. The composite ink of any of the preceding embodiments, wherein the composite ink is free or substantially free of solid powder fillers having a particle size less than 100 nm.

[0150] Embodiment 29. The composite ink of any of the previous embodiments, wherein the solid powder filler has an average particle aspect ratio of 1 to 1.1.

[0151] Embodiment 30. The composite ink of any of the previous embodiments, wherein the solid powder filler is free or substantially free of irregularly shaped particles.

[0152] Embodiment 31. The solid powder filler comprises 30 ml 2 / g or less, 20m 2 / g or less than 10m 2 3. The composite ink of any of the previous embodiments, characterized in that it has an average BET specific surface area of ​​less than 1 / g.

[0153] Embodiment 32. The solid powder filler has an average particle size of 0.1 μm to 1 μm, 0.1 μm to 3 μm, or 0.1 μm to 5 μm; and The solid powder filler is 30 ml 2 / g or less, 20m 2 / g or less than 10m 2 / g 3. A composite ink according to any of the preceding embodiments.

[0154] Embodiment 33. The composite ink of any of the previous embodiments, wherein the solid powder filler has a functionalized outer surface.

[0155] Embodiment 34. The composite ink of embodiment 33, wherein the outer surface of the solid powder filler is functionalized with (meth)acrylate moieties.

[0156] Embodiment 35. The composite ink of any of the preceding embodiments, wherein the solid powder filler is present in an amount of 20 to 85% by weight, based on the total weight of the composite ink, or in an amount of 10 to 75% by volume, based on the total volume of the composite ink.

[0157] Embodiment 36. The composite ink of any of the preceding embodiments, wherein the solid powder filler is present in an amount of 45 to 70% by weight, based on the total weight of the composite ink, or in an amount of 25 to 55% by volume, based on the total volume of the composite ink.

[0158] Embodiment 37. The composite ink of any of the preceding embodiments, wherein the solid powder filler is present in an amount of 55 to 65% by weight, based on the total weight of the composite ink, or in an amount of 38 to 48% by volume, based on the total volume of the composite ink.

[0159] Embodiment 38. The composite ink of any of the preceding embodiments, wherein the carrier ink is present in an amount of 10 to 80% by weight, based on the total weight of the composite ink.

[0160] Embodiment 39. The composite ink of any of the preceding embodiments, wherein the carrier ink is present in an amount of 25 to 55% by weight, based on the total weight of the composite ink.

[0161] Embodiment 40. The composite ink of any of the preceding embodiments, wherein the carrier ink is present in an amount of 30 to 45% by weight, based on the total weight of the composite ink.

[0162]

[0032] Embodiment 41. The composite ink of any of the preceding embodiments, wherein the composite ink further comprises a dispersant.

[0163] Embodiment 42. The composite ink of embodiment 41, wherein the dispersant is present in an amount of 0.2 to 5% by weight relative to the amount of the solid powder filler.

[0164] Embodiment 43. The composite ink of any of the preceding embodiments, wherein the composite ink is not a Bingham fluid at 30° C.

[0165] Embodiment 44. A method of printing a three-dimensional article, comprising: Providing a composite ink according to any one of embodiments 1 to 43; and Selectively solidifying the layer of composite ink to form an article. A method comprising:

[0166] In accomplishing the various objectives of the present invention, various embodiments of the present invention have been described. It is to be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. 1. A composite ink for use in a three dimensional printing system, comprising: a carrier ink comprising a curable material; and a solid powder filler dispersed in said carrier ink; Including, the composite ink, in an uncured state, has a highly accelerated life test (HALT) score of at least 2 when tested at 65°C for at least 14 days; and / or The composite ink, in an uncured state, has an average loss factor tan δ of less than or equal to 2 over an angular frequency range of 0.5 to 5 rad / s. A composite ink characterized by:

2. 10. The composite ink of claim 1, wherein the composite ink has a HALT score of 3 when tested at 65°C for at least 14 days.

3. 10. The composite ink of claim 1, wherein the composite ink has a shear viscosity of 5000 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3.

4. 3. The composite ink of claim 2, wherein the composite ink has a shear viscosity of 3000 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3.

5. 10. The composite ink of claim 1, wherein the composite ink has a shear viscosity of 2000 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3.

6. 3. The composite ink of claim 2, wherein the composite ink has a shear viscosity of 500 to 1500 cps at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 3.

7. The composite ink of claim 1 , wherein the curable material of the carrier ink comprises one or more monomeric curable materials.

8. 8. The composite ink of claim 7, wherein the one or more monomeric curable materials are present in the carrier ink in an amount of 15% to 85% by weight, based on the total weight of the carrier ink.

9. The composite ink of claim 1 , wherein the curable material of the carrier ink comprises one or more oligomeric curable materials.

10. 10. The composite ink of claim 9, wherein the one or more oligomeric curable materials are present in the carrier ink in an amount of 15% to 85% by weight, based on the total weight of the carrier ink.

11. The composite ink of claim 1 , wherein the curable material of the carrier ink comprises a combination of one or more monomeric curable materials and one or more oligomeric curable materials.

12. The composite ink of claim 1 , wherein the curable material of the carrier ink comprises one or more acrylate, methacrylate, or vinyl species.

13. The composite ink of claim 1 , wherein the curable material of the carrier ink comprises one or more epoxy species.

14. The composite ink of claim 1 , wherein all or substantially all of the curable materials of the carrier ink are curable by free radical polymerization.

15. The composite ink of claim 1 , wherein the carrier ink further comprises a photoinitiator component.

16. 16. The composite ink of claim 15, wherein the photoinitiator component is present in the carrier ink in an amount of 5% by weight or less.

17. The composite ink of claim 1 , wherein the carrier ink further comprises an inhibitor component.

18. 18. The composite ink of claim 17, wherein the inhibitor component is present in the carrier ink in an amount of 1% by weight or less.

19. 10. The composite ink of claim 1, wherein the carrier ink has a shear viscosity of 200 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 2.

20. 3. The composite ink of claim 2, wherein the carrier ink has a shear viscosity of 100 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 2.

21. 10. The composite ink of claim 1, wherein the carrier ink has a shear viscosity of 50 cps or less at 30° C. based on a shear rate of 1.0 (1 / s), as measured according to the shear rate sweep procedure of Example 2.

22. The solid powder filler is SiO ２ The composite ink of claim 1 , characterized in that it comprises a powder.

23. The solid powder filler is amorphous SiO ２ 23. The composite ink of claim 22, comprising:

24. 2. The composite ink of claim 1, wherein the solid powder filler has an average particle size of 0.1 μm to 5 μm.

25. 2. The composite ink of claim 1, wherein the solid powder filler has an average particle size of 0.1 μm to 2 μm.

26. 2. The composite ink of claim 1, wherein the solid powder filler has an average particle size of 0.1 μm to 1 μm.

27. 2. The composite ink of claim 1, wherein the solid powder filler has an average particle size of 0.1 μm to 0.5 μm.

28. 10. The composite ink of claim 1, wherein the composite ink is free or substantially free of solid powder fillers having a particle size less than 100 nm.

29. 10. The composite ink of claim 1, wherein the solid powder filler has an average particle aspect ratio of 1 to 1.

1.

30. 10. The composite ink of claim 1, wherein the solid powder filler is free or substantially free of irregularly shaped particles.

31. The solid powder filler is 30 m ２ 10. The composite ink of claim 1, having an average BET specific surface area of ​​less than 1000 nm / g.

32. The solid powder filler has an average particle size of 0.1 μm to 1 μm; and The solid powder filler is 30 m ２ / g or less The composite ink according to claim 1 .

33. The composite ink of claim 1 , wherein the solid powder filler has a functionalized outer surface.

34. 34. The composite ink of claim 33, wherein the outer surface of the solid powder filler is functionalized with (meth)acrylate moieties.

35. 2. The composite ink of claim 1, wherein the solid powder filler is present in an amount of 20 to 85% by weight based on the total weight of the composite ink, or in an amount of 10 to 75% by volume based on the total volume of the composite ink.

36. 2. The composite ink of claim 1, wherein the solid powder filler is present in an amount of 45 to 70% by weight based on the total weight of the composite ink, or in an amount of 25 to 55% by volume based on the total volume of the composite ink.

37. 2. The composite ink of claim 1, wherein the solid powder filler is present in an amount of 55 to 65% by weight based on the total weight of the composite ink, or in an amount of 38 to 48% by volume based on the total volume of the composite ink.

38. 10. The composite ink of claim 1, wherein the carrier ink is present in an amount of 10 to 80% by weight based on the total weight of the composite ink.

39. 10. The composite ink of claim 1, wherein the carrier ink is present in an amount of 25 to 55% by weight based on the total weight of the composite ink.

40. 10. The composite ink of claim 1, wherein the carrier ink is present in an amount of 30 to 45% by weight based on the total weight of the composite ink.

41. The composite ink of claim 1 , further comprising a dispersant.

42. 42. A composite ink according to claim 41, characterized in that the dispersant is present in an amount of 0.2 to 5% by weight compared to the amount of the solid powder filler.

43. 10. The composite ink of claim 1, wherein the composite ink is not a Bingham fluid at 30[deg.]C.

44. 1. A method for printing a three-dimensional article, comprising: Providing a composite ink according to claim 1; and Selectively solidifying the layer of composite ink to form an article. A method comprising:

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