Additives for build materials and related printed 3D articles

Abstract

Described herein are additives for three-dimensional build materials or inks that, in some embodiments, can impart one or more structural reinforcements to articles printed with the build materials. In one aspect, a polymerizable liquid includes at least one additive including a plurality of cyclizable polymerizable functional groups separated by an aliphatic linker or an alkylene oxide linker.

Description

[0001] TECHNICAL FIELD The present invention relates to additives for three-dimensional build materials, and in particular to additives that can impart structural enhancements to articles printed from the build materials.

[0002] BACKGROUND 3D printers employ build materials, also referred to as inks, to form various 3D objects, articles, or parts according to computer-generated files. In some cases, the build material is a solid at ambient temperature and is converted to a liquid at an elevated jetting temperature. In other cases, the build material is a liquid at ambient temperature.

[0003] The build materials can include a wide variety of chemical species. The chemical species to be included in the build material can be selected according to a variety of considerations, including but not limited to the desired chemical and / or mechanical properties of the printed article and the operating parameters of the 3D printing device. For example, ultraviolet (UV) curable acrylate formulations can generally print parts at high resolution on DLP systems. However, in many cases, the resulting parts lack desirable mechanical properties and can be easily broken or undergo other degradation pathways. Such degradation pathways impair article performance, leading to premature failure.

[0004] SUMMARY In view of the foregoing, described herein are additives for three-dimensional build materials or inks that, in some embodiments, can impart one or more structural enhancements to articles printed from the build materials. In one aspect, a polymerizable liquid includes at least one additive that includes a plurality of cyclizable polymeric functional groups separated by aliphatic linkers or oxyalkylene linkers, the cyclizable polymeric functional groups having the following formula: In some embodiments, when present, the oxyalkylene linkers are oligomeric or polymeric.

[0005] In some embodiments, the polymerizable liquid further includes an oligomeric curable material, a monomeric curable material, or a mixture thereof. In some embodiments, the polymerizable liquid can include a photoinitiator component for initiating polymerization via one or more radical mechanisms.

[0006] In another aspect, described herein are methods of printing three-dimensional articles. In some embodiments, the methods include providing a polymerizable liquid that includes an oligomeric curable material, a monomeric curable material, or a mixture thereof, and at least one additive that includes a plurality of cyclizable polymeric functional groups separated by aliphatic linkers or oxyalkylene linkers, the cyclizable polymeric functional groups having the following formula: The polymerizable liquid is printed and cured to form an article. In some embodiments, the article is formed via a layer-by-layer method, in which layer formation is effected via deposition and curing of layers of the polymerizable liquid. As further described herein, the polymerizable liquid can further include a photoinitiator component, and curing of the liquid can occur by irradiating the polymerizable liquid with light of an appropriate wavelength to initiate free radical polymerization.

[0007] These and other embodiments are described further in the detailed description below.

[0008] DETAILED DESCRIPTION The embodiments described herein can be more readily understood by reference to the following detailed description and examples. However, the elements, devices, and methods described herein are not limited to the specific embodiments presented in the detailed description and examples. It is recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and alterations to the described embodiments will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention.

[0009] Further, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of "1.0 to 10.0" should be considered to include any and all subranges between (and inclusive of) the minimum value of 1.0 and the maximum value of 10.0, e.g., 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9.

[0010] Unless otherwise expressly stated, all ranges disclosed herein are to be understood as encompassing the end points of the ranges. For example, a range of "between 5 and 10" is to be understood as including the end points 5 and 10.

[0011] Further, when the phrase "at most" is used in association with a quantity or amount, it is to be understood that the quantity is at least a detectable amount or quantity. For example, a material present in an amount of "at most" a specified amount can be present in a detectable amount up to and including the specified amount.

[0012] The terms "three-dimensional printing system," "three-dimensional printer," "printing," and the like generally describe various solid freeform fabrication techniques for making three-dimensional articles or objects by selective deposition, jetting, fused deposition modeling, multi-jet modeling, and other additive manufacturing techniques for making three-dimensional objects using a build material or ink that are presently known or that can become known in the future.

[0013] In one aspect, the polymerizable liquid includes at least one additive that includes a plurality of cyclizable polymeric functional groups separated by aliphatic or oxyalkylene linkers, the cyclizable polymeric functional groups having the formula: , wherein is a point of attachment of the cyclizable polymerization functional group to the linker. In some embodiments, the additive has the following formula: where L is an aliphatic linker or an oxyalkylene linker. In some embodiments, when present, the oxyalkylene linker can be oligomeric or polymeric. In such embodiments, the additive can have the following formula: where R 1 is hydrogen or an alkyl group (e.g., a C1-C10 alkyl group, where "Cn" alkyl is understood to expressly include "n" carbon atoms), and m is an integer from 1 to 20. In some embodiments, the additive comprises three or more cyclizable polymerization functional groups.

[0014] The additive can be present in the polymerizable liquid in any amount consistent with the technical objectives of improving or enhancing the mechanical properties of a three-dimensional article printed from the polymerizable liquid. In some embodiments, the amount of additive is selected in accordance with various considerations, including but not limited to the desired mechanical property set of the article printed from the polymerizable liquid, the printing conditions, and / or the chemical properties of other species in the polymerizable liquid. In some embodiments, one or more additives having a formula described herein are present in the polymerizable liquid in a total amount of 5 to 40 weight percent (wt.%), 5 to 30 wt.%, 7 to 30 wt.%, 10 to 30 wt.%, or 10 to 20 wt.%, based on the total weight of the polymerizable liquid. It is of course further understood that the total weight of the polymerizable liquid is 100 wt.%.

[0015] The polymerizable liquid can further comprise an oligomeric curable material, a monomeric curable material, or a mixture thereof. For reference purposes herein, a curable material comprises a chemical species that includes one or more curable moieties or polymerizable moieties. For reference purposes herein, a "polymerizable moiety" comprises a moiety that can be polymerized or cured to provide a printed 3D article or object. Such polymerization or curing can be performed in any manner consistent with the purposes of the present disclosure. For example, in some embodiments, polymerization or curing comprises irradiating the polymerizable or curable material with electromagnetic radiation having sufficient energy to initiate a polymerization or crosslinking reaction. For example, in some cases, ultraviolet (UV) radiation can be used. Thus, in some cases, the polymerizable moiety comprises a photopolymerizable moiety or a photocurable moiety, such as a UV polymerizable moiety. In some embodiments, the curable materials described herein are photopolymerizable or photocurable at wavelengths ranging from about 300 nm to about 400 nm, or from about 320 nm to about 380 nm. Alternatively, in other cases, the curable material is photopolymerizable at visible wavelengths of the electromagnetic spectrum.

[0016] Further, in some cases, the polymerization reaction includes a free radical polymerization reaction, such as a free radical polymerization reaction between unsaturation points, including ethylenic unsaturation points. Other polymerization reactions can also be used. As understood by one of ordinary skill in the art, the polymerization reaction used to polymerize the curable materials described herein can include the reaction of a variety of “monomers” or chemical species having one or more functional groups or moieties that can react with one another to form one or more covalent bonds.

[0017] One non-limiting example of a polymerizable portion of the curable materials described herein is an ethylenic unsaturation portion, such as a vinyl portion, an allyl portion, or a (meth)acrylate portion, where the term “(meth)acrylate” throughout the present disclosure includes an acrylate or a methacrylate, or a mixture or combination thereof.

[0018] Further, the oligomeric curable materials and / or monomeric curable materials described herein can include a monofunctional curable species, a difunctional curable species, a trifunctional curable species, a tetrafunctional curable species, a pentafunctional curable species, or a higher functional curable species. In the present context for reference purposes, a “monofunctional” curable species includes a chemical species that includes one curable portion or polymerizable portion. Similarly, a “difunctional” curable species includes a chemical species that includes two curable portions or polymerizable portions; a “trifunctional” curable species includes a chemical species that includes three curable portions or polymerizable portions; a “tetrafunctional” curable species includes a chemical species that includes four curable portions or polymerizable portions; and a “pentafunctional” curable species includes a chemical species that includes five curable portions or polymerizable portions. Thus, in some embodiments, a monofunctional curable material of the polymerizable liquid described herein includes a mono(meth)acrylate, a difunctional curable material of the polymerizable liquid described herein includes a di(meth)acrylate, a trifunctional curable material of the polymerizable liquid described herein includes a tri(meth)acrylate, a tetrafunctional curable material of the polymerizable liquid described herein includes a tetra(meth)acrylate, and a pentafunctional curable material of the polymerizable liquid described herein includes a penta(meth)acrylate. Other monofunctional curable materials, difunctional curable materials, trifunctional curable materials, tetrafunctional curable materials, and pentafunctional curable materials can also be used.

[0019] Further, in some cases, the mono-functional, di-functional, tri-functional, tetra- functional, and penta-functional curable materials can comprise relatively low molecular weight species, i.e., monomeric species (e.g., species having a molecular weight of less than 300, less than 200, or less than 100); or relatively high molecular weight species, i.e., oligomeric species (e.g., species having a molecular weight (e.g., weight average molecular weight in the case of species having a molecular weight distribution) of greater than 300, greater than 400, greater than 500, or greater than 600 and optionally less than 10,000).

[0020] In general, any oligomeric curable material or combination of oligomeric curable materials that are consistent with the purposes of the present disclosure can be used in the polymerizable liquids described herein. In some cases, the oligomeric curable material comprises a polyester acrylate oligomer, a polyester (meth)acrylate oligomer, a urethane acrylate oligomer, a urethane (meth)acrylate oligomer, a polyether urethane oligomer, or an epoxy (meth)acrylate oligomer. Further, in some embodiments, the oligomeric curable materials described herein comprise an aliphatic polyester urethane acrylate oligomer and / or an acrylate amine oligomeric resin, such as EBECRYL 7100.

[0021] Some non-limiting examples of commercially available oligomeric curable materials useful in some embodiments described herein include the following: an alkoxylated tetrahydrofurfuryl acrylate commercially available under the trade designation SR 611 from SARTOMER; a mono-functional urethane acrylate commercially available under the trade designation GENOMER 1122 from RAHN USA; an aliphatic urethane diacrylate commercially available under the trade designation EBECRYL 8402 from ALLNEX; a multi-functional acrylate oligomer commercially available under the trade designation BR-952 from DYMAX Corporation; an aliphatic polyether urethane acrylate commercially available under the trade designation BR-371S from DYMAX Corporation; and a polyether urethane methacrylate commercially available under the trade designation BR-541 MD from DYMAX Corporation. Other commercially available oligomeric curable materials can also be used.

[0022] In some cases, urethane (meth)acrylates suitable for use in the polymerizable liquids described herein can be prepared in known manner, 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. Suitable methods are disclosed, inter alia, in EP-A 114 982 and EP-A 133 908. In some cases, the weight average molecular weight of such (meth)acrylate oligomers can be about 500 to 6,000. Urethane (meth)acrylates are also commercially available from SARTOMER under the product names CN980, CN981, CN975, and CN2901. In some embodiments, urethane acrylate oligomers are used in the polymerizable liquids described herein. Suitable urethane acrylates can include the difunctional aliphatic urethane acrylates available from DYMAX Corporation under the trade names BR-741 and BR-970. In some embodiments, the oligomeric curable material comprises an aliphatic polyester urethane acrylate or an aliphatic polyether urethane acrylate. Commercial examples of these oligomer classes are available from DYMAX Corporation under the trade names BR-7432 and BR-543, respectively.

[0023] The oligomeric curable material can be present in the polymerizable liquids described herein in any desired amount. In some embodiments, the total amount of oligomeric curable material present is 5-50 wt%, 5-40 wt%, 5-35 wt%, 5-30 wt%, 10-50 wt%, 10-40 wt%, 10-35 wt%, 10-30 wt%, 15-50 wt%, 15-40 wt%, 15-35 wt%, 15-30 wt%, 20-50 wt%, 20-40 wt%, 20-35 wt%, or 20-30 wt%, based on the total weight of the polymerizable liquid.

[0024] In some embodiments, the polymerizable liquids described herein can include a monomeric curable material. In some cases, the monomeric curable material of the polymerizable liquids described herein comprises one or more (meth)acrylate species, such as one or more mono-functional (meth)acrylates, di-functional (meth)acrylates, tri-functional (meth)acrylates, tetra-functional (meth)acrylates, and / or penta-functional (meth)acrylates. For example, in some embodiments, the monomeric curable material comprises 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-hydroxypropyl (meth)acrylate, or 3-hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-ethoxypropyl (meth)acrylate, or 3-ethoxypropyl (meth)acrylate, tetrahydrofurfuryl methacrylate, isobornyl (meth)acrylate, dicyclopentyl methacrylate, 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 monomeric curable material comprises one or more of allyl acrylate, allyl methacrylate, triethylene glycol di(meth)acrylate, tricyclodecane dimethanol diacrylate, and cyclohexane dimethanol diacrylate. Further, in some cases, the monomeric curable material comprises a diacrylate and / or dimethacrylate of an aliphatic diol, a cycloaliphatic diol, or an aromatic diol, including 1,3-butanediol 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'-dihydroxydiphenyl, bisphenol A, bisphenol F, or bisphenol S. The monomeric curable materials described herein can also comprise 1,1-trimethylolpropane tri(meth)acrylate, pentaerythritol monohydroxy tri(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate, bis(trimethylolpropane) tetra(meth)acrylate, and / or acryloyl morpholine.

[0025] Non-limiting examples of commercially available monomer curable materials useful in some embodiments described herein include the following: isobornyl acrylate (IBOA) commercially available under the trade designation SR 506 from SARTOMER; isobornyl methacrylate commercially available under the trade designation SR 423A from SARTOMER; monofunctional acrylate monomer commercially available under the trade designation SR 420 from SARTOMER; cyclic trimethylolpropane formal acrylate monomer commercially available under the trade designation SR 531 from SARTOMER; triethylene glycol diacrylate commercially available under the trade designation SR 272 from SARTOMER; triethylene glycol dimethacrylate commercially available under the trade designation SR 205 from SARTOMER; tricyclodecane dimethanol diacrylate commercially available under the trade designation SR 833S from SARTOMER; tris(2-hydroxyethyl)isocyanurate triacrylate commercially available under the trade designation SR 368 from SARTOMER; 2-phenoxyethyl acrylate commercially available under the trade designation SR 339 from SARTOMER; ethoxylated (3 moles) bisphenol A diacrylate commercially available under the trade designation SR 349 from SARTOMER; cyclic monofunctional acrylate commercially available under the trade designation GENOMER 1120 from RAHN USA Corp.; dipentaerythritol pentaacrylate commercially available under the trade designation SR 399 LV from SARTOMER; and dicyclopentyl acrylate and / or dicyclopentyl methacrylate commercially available under the trade designation FA-513 M from Showa Denko Materials. Other commercially available monomer curable materials can also be used.

[0026] In some embodiments, the isocyanurate polyacrylate has the following formula: wherein R 1 -R 3 is independently selected from the group consisting of hydrogen and alkyl (e.g., C1-C10 alkyl), and m, n, and p are independently integers ranging from 1 to 10.

[0027] In some embodiments, the monomer curable material includes a heterocycle including two or more unsaturated substituents. The substituted heterocycle may, for example, include three unsaturated substituents. In some embodiments, the heterocycle can be polyallylated. When polyallylated, the heterocycle includes two or more allyl substituents. For example, the polyallylated heterocycle can include a polyallyl isocyanurate. Alternatively, the heterocycle including two or more unsaturated substituents can have the following formula: wherein R 4 -R 6independently selected from the group consisting of hydrogen and alkyl (e.g., C1-C10 alkyl), and m, n, and p are independently integers ranging from 1 to 10.

[0028] In some embodiments, the monomer-curable material comprises a cyclic carbonate (meth)acrylate monomer. For example, the monomer-curable material can comprise a cyclic carbonate (meth)acrylate monomer having the following formula: wherein R1is a linear or branched C1-C6 alkylene moiety; and wherein R2is H or CH3.

[0029] The monomer-curable material can be present in the polymerizable liquid described herein in any desired amount. In some embodiments, the monomer-curable material is present in an amount of 5-80 wt%, 5-75 wt%, 5-70 wt%, 5-60 wt%, 10-80 wt%, 10-75 wt%, 10-70 wt%, 10-60 wt%, 15-80 wt%, 15-75 wt%, 15-70 wt%, 15-60 wt%, 20-80 wt%, 20-75 wt%, 20-70 wt%, 20-60 wt%, 25-80 wt%, 25-75 wt%, 25-70 wt%, 25-60 wt%, 30-80 wt%, 30-75 wt%, 30-70 wt%, 30-60 wt%, 35-80 wt%, 35-75 wt%, 35-70 wt%, or 35-60 wt%, based on the total weight of the polymerizable liquid. The monomer-curable material can comprise one monomer species or a mixture of any monomer species described above.

[0030] In some embodiments, the polymerizable liquid comprises polymer particles dispersed in a curable carrier. The polymer particles can have any composition and / or structure consistent with achieving the technical purposes described herein. The polymer particles can comprise an elastomer, a thermoplastic, a thermoset, or any combination thereof. The particular compositional properties of the polymer particles can be selected according to the desired mechanical properties of the printed article. In some embodiments, the polymer particles exhibit a core-shell structure. For example, the polymer particles can comprise an elastomer core and a thermoplastic shell or a thermoset shell. In some embodiments, the composite resin comprising core-shell particles in the curable resin is available under the trade name Kane Ace® from Kaneka Texas Corporation. ® MX is commercially available from Kaneka Texas Corporation. The polymer particles can have any desired size. In some embodiments, the polymer particles have a size of less than 1 μm. For example, the polymer particles can have an average size of 50 nm to 500 nm. In other embodiments, the polymer particles can have an average size of greater than 1 μm (e.g., 5 μm to 50 μm).

[0031] The polymer particles can be present in the curable carrier in any desired amount. In some embodiments, the polymer particles are present in an amount of 20-70 wt% or 30-60 wt%, based on the total weight of the composite resin. Further, the composite resin can be present in the polymerizable liquid in any amount consistent with the technical purposes described herein. For example, the composite resin can be present in an amount of at least 20 wt% or at least 30 wt%, based on the total weight of the polymerizable liquid. In some embodiments, the composite resin is present in an amount of 5-30 wt%, based on the total weight of the polymerizable liquid.

[0032] The polymerizable liquids described herein can further comprise a photoinitiator component for initiating polymerization of one or more components of the liquid upon exposure to light of an appropriate wavelength. In some embodiments, the photoinitiator component can initiate polymerization of the additives described herein, which comprise one or more unsaturated points that can polymerize via a free radical mechanism. Similarly, a photoinitiator can be employed to polymerize the (meth)acrylate component. In some embodiments, the additives described herein can copolymerize with the (meth)acrylate component. In other embodiments, the additives and the (meth)acrylate component independently polymerize.

[0033] Any photoinitiator consistent with the purposes of the present disclosure can be used. In some embodiments, the photoinitiator comprises an a-cleavage type (monomolecular decomposition process) photoinitiator or a hydrogen abstraction photoinitiator-tertiary amine synergist, which is operable to absorb light, preferably between about 250 nm and about 420 nm or between about 300 nm and about 385 nm, to generate free radicals.

[0034] Examples of a-cleavage photoinitiators are Irgacure 184 (CAS 947-19-3), Irgacure 369 (CAS 119313-12-1), and Irgacure 819 (CAS 162881-26-7). An example of a photoinitiator-amine combination is Darocur BP (CAS 119-61-9) with diethylaminoethyl methacrylate.

[0035] In some cases, suitable photoinitiators include benzoin; benzoin ethers, such as benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether, benzoin phenyl 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, including 2-methylanthraquinone, 2- ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, and 2- pentylanthraquinone; triphenylphosphine; benzoylphosphine oxides, such as 2,4,6- trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO); benzophenones, such as benzophenone and 4,4'-bis(N,N'-dimethylamino)benzophenone; thioxanthone and xanthone; acridine derivatives; phenazine derivatives; quinoxaline derivatives; or 1-phenyl-1,2-propanedione; 2-O-benzoyl oxime; 1-aminophenyl ketones; or 1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone, phenyl 1-hydroxyisopropyl ketone, and 4-isopropylphenyl 1- hydroxyisopropyl ketone.

[0036] Suitable photoinitiators can also include those 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 (= 2-hydroxy-2,2-dimethylacetophenone). In some cases, suitable photoinitiators include those operable for use with Ar laser radiation sources, including benzil ketals, such as benzil dimethyl ketal. In some embodiments, the photoinitiator includes an a-hydroxyphenyl ketone, benzil dimethyl ketal, or 2,4,6- trimethylbenzoyldiphenylphosphine oxide, or mixtures thereof.

[0037] In some cases, another class of suitable photoinitiators includes ionic dye-counterion compounds capable of absorbing actinic radiation and generating free radicals for polymerization initiation. In some embodiments, the polymerizable liquid containing the ionic dye-counterion compound can be polymerized upon exposure to visible light in a tunable wavelength range of about 400 nm to about 700 nm. Ionic dye-counterion compounds and their mode of operation are disclosed in EP-A-0 223 587 and U.S. Pat. Nos. 4,751,102; 4,772,530; and 4,772,541.

[0038] The photoinitiator can be present in the polymerizable liquids described herein in any amount consistent with the purposes of the present disclosure. In some embodiments, the photoinitiator is present in an amount of up to about 5% by weight, based on the total weight of the polymerizable liquid. In some cases, the photoinitiator is present in an amount ranging from about 0.1% to about 5% by weight.

[0039] Furthermore, in some embodiments, the polymerizable liquid described herein may further comprise one or more sensitizers. Sensitizers may be added to enhance the effectiveness of one or more photoinitiators that may also be present. Any sensitizer consistent with the purposes of this disclosure may be used. In some cases, the sensitizer includes isopropylthioxanthone (ITX) or 2-chlorothioxanthone (CTX).

[0040] The sensitizer may be present in the polymerizable liquid in any amount consistent with the purposes of this disclosure. In some embodiments, the sensitizer is present in an amount of about 0.1% to about 2% by weight or about 0.5% to about 1% by weight, based on the total weight of the polymerizable liquid.

[0041] In some embodiments, one or more UV absorbers and / or light stabilizers may be present in the polymerizable liquid. For example, in some embodiments, one or more UV absorbers and / or light stabilizers may be present in an amount of 0.1-2% by weight based on the total weight of the polymerizable liquid. In some embodiments, the UV absorber and / or light stabilizer is marketed under the trade name TINUVIN. ® Purchased from BASF in Florham Park, New Jersey.

[0042] Furthermore, this document describes a method for printing three-dimensional articles. In some embodiments, the method includes providing a polymerizable liquid comprising an oligomeric curable material, a monomeric curable material, or a mixture thereof, and at least one additive, the additive comprising a plurality of cyclizable polymerizable functional groups separated by aliphatic or olefinic joints, the cyclizable polymerizable functional groups having the following formula: . The polymerizable liquid is printed and cured to form an article. In some embodiments, the article is formed via a layer-by-layer method, wherein layer formation is performed via the deposition and curing of polymerizable liquid layers. As further described herein, the polymerizable liquid may further comprise a photoinitiator component, and curing of the liquid can occur by irradiating the polymerizable liquid with light of an appropriate wavelength to initiate free radical polymerization.

[0043] In some embodiments, during formation of a three-dimensional article, layers of polymerizable liquid can be deposited according to an image of the 3D article in a computer readable format. The polymerizable liquid can be deposited according to pre-selected computer-aided design (CAD) parameters. Further, in some cases, one or more of the polymerizable liquid layers described herein have a thickness of about 10 μιη to about 100 μιη, about 10 μιη to about 80 μιη, about 10 μιη to about 50 μιη, about 20 μιη to about 100 μιη, about 20 μιη to about 80 μιη, or about 20 μιη to about 40 μιη. Other thicknesses are also possible.

[0044] Further, it should be appreciated that the methods of printing a 3D article described herein can include so-called "multi-jet" or "stereolithographic" 3D printing methods. For example, in some cases, a multi-jet method of printing a 3D article includes selectively depositing a layer of a polymerizable liquid described herein onto a substrate, such as a build pad of a 3D printing system. Further, in some embodiments, the methods described herein further include supporting at least one of the layers of polymerizable liquid with a support material. Any support material consistent with the purposes of the present disclosure can be used.

[0045] It is also possible to form a 3D article from a polymerizable liquid described herein using stereolithography. For example, in some cases, a method of printing a 3D article includes holding a polymerizable liquid in a container and selectively applying energy to the polymerizable liquid in the container to solidify at least a portion of the polymerizable liquid, thereby forming a solidified layer defining a cross-section of the 3D article. Further, the methods described herein can further include raising or lowering the solidified layer to provide a new layer of polymerizable liquid or a second layer of polymerizable liquid, and then again selectively applying energy to the polymerizable liquid in the container to solidify at least a portion of the new polymerizable liquid or the second polymerizable liquid defining a second cross-section of the 3D article. Further, the first cross-section and the second cross-section of the 3D article can be bonded or adhered to one another in the z-direction (or a build direction corresponding to the direction of raising or lowering noted above) by the application of energy to solidify the polymerizable liquid. Further, selectively applying energy to the polymerizable liquid in the container can include applying electromagnetic radiation, such as UV radiation and / or visible light radiation, having an energy sufficient to initiate polymerization of the polymerizable material as described herein. Further, in some cases, the raising or lowering of the solidified layer of polymerizable liquid is performed using a lift platform disposed in the container of fluid build material. The methods described herein can also include planarizing the new layer of polymerizable liquid provided by raising or lowering the lift platform. In some cases, such planarization can be performed by a squeegee or roller.

[0046] Articles printed according to the methods described herein can exhibit one or more desirable mechanical properties due to the composition and microstructure of the printed article. 3D articles printed from the polymerizable liquids described herein can also exhibit a tensile modulus of 1900-2700 MPa. In some embodiments, the 3D printed articles can exhibit a tensile strength of greater than 40 MPa, such as a tensile strength of 40-70 MPa or 50-65 MPa. The values of tensile strength and tensile modulus provided herein can be determined according to ASTM D638.

[0047] In addition, 3D articles printed from the polymerizable liquids described herein can exhibit an elongation at break of at least 3%, at least 5%, or at least 10% (e.g., when determined according to ASTM D638). In some embodiments, the printed 3D articles have an elongation at break of greater than 10% when determined by ASTM D638, such as an elongation at break of 10-20%. 3D articles printed from the polymerizable liquids described herein can also exhibit a heat deflection temperature (HDT) of at least 90°C (e.g., 100-260°C). In some embodiments, 3D articles printed from the polymerizable liquids described herein can have an HDT of greater than 300°C. The HDT is measured using DMA according to ASTM D648 at 0.455 MPa.

[0048] In addition, in some cases, 3D articles printed from the polymerizable liquids described herein (and the polymerizable liquids themselves when polymerized) can have other desirable composition parameters or characteristics. For example, in some embodiments, the 3D articles or polymerizable liquids described herein have a relatively high stress relaxation value or residual stress (e.g., measured according to ASTM E837 or ASTM D638 Type IV). In addition, in some embodiments, the 3D articles or polymerizable liquids described herein have a relatively high stress relaxation / residual stress value in water at 37°C. For example, in some preferred embodiments, the 3D articles or polymerizable liquids described herein have a stress relaxation / residual stress value or stress relaxation residual load (5% strain) of greater than 1 Newton (N) in water at 37°C when measured according to ASTM D638 Type IV, such as a value of 1-5 N, 1-3 N, 1-2 N, or 1-1.5 N.

[0049] Furthermore, 3D articles printed from the polymerizable liquids described herein (and, upon polymerization, the polymerizable liquids themselves) can resist hydrolysis or degradation due to water exposure. For example, in some cases, the polymerizable liquids described herein (or 3D articles printed from them) can have hydrolysis resistance with respect to maintaining certain mechanical properties (e.g., flexural strength, flexural modulus, and / or elongation at break) after exposure to water. Thus, the 3D articles or polymerizable liquids described herein can exhibit one, two, or all three of the following hydrolysis resistance metrics (due to their composition / microstructure): at least 80%, at least 85%, at least 90%, or at least 95% hydrolysis resistance of flexural strength (FS); at least 80%, at least 85%, at least 90%, or at least 95% hydrolysis resistance of flexural modulus (FM); and at least 80%, at least 85%, at least 90%, or at least 95% hydrolysis resistance of elongation at break (EOB).

[0050] The above metrics are based on "water exposure" of a 3D article (or polymerized liquid) as follows. After printing a 3D article, the relevant properties (i.e., flexural strength, flexural modulus, or elongation at break) of a test sample (e.g., a 3D article formed from a polymerizable liquid) are measured (e.g., within 12 hours). The test sample is then submerged in water at 37 °C for 24 hours. After this submersion period, the test sample is dried, and the relevant properties (i.e., flexural strength, flexural modulus, or elongation at break) are again measured in the same manner as previously (e.g., using ASTM D638, and providing output in MPa). The post-submersion measurement (result) is then compared to the pre-submersion measurement (result). For example, if a given test sample has a flexural strength of 100 MPa prior to water submersion, and a flexural strength of 95 MPa after 24 hours of water submersion, the flexural strength hydrolysis resistance would be 95% (from the comparison of 95 MPa to 100 MPa).

[0051] Furthermore, in some embodiments, water submersion can even improve certain properties, such as elongation at break. For example, in some cases, the 3D articles described herein have an EOB hydrolysis resistance of 80-130%, 80-125%, 90-125%, or 90-120%. In some cases, the flexural strength hydrolysis resistance and / or flexural modulus hydrolysis resistance can also be as high as 110% or 105%, although it will be understood that 100% is a typical maximum.

[0052] Furthermore, in some preferred embodiments, 3D articles printed from the polymerizable liquids described herein (and, upon polymerization, the polymerizable liquids themselves) have one, two, three, four, five, six, or all seven of the following composition parameters: (1) a stress relaxation / residual stress value (or stress relaxation residual load, 5% strain) in water at 37 °C greater than 1 N (e.g., 1-5 N, 1-3 N, 1-2 N, or 1-1.5 N) when measured according to ASTM D638 Type IV; (2) a stress relaxation initial load (5% strain) in water at 37 °C less than 35 N or less than 30 N (e.g., 15-35 N or 20-35 N) when measured according to ASTM D638 Type IV; (3) a tensile strength greater than 40 MPa (e.g., 40-70 MPa or 50-65 MPa) when measured according to ASTM D638 Type IV; (4) a flexural strength greater than 35 MPa or greater than 40 MPa (e.g., 35-50 MPa or 40-50 MPa) when measured according to ISO 20795-2; (5) a flexural modulus greater than 1000 MPa (e.g., 1000-2000 MPa or 1000-1500 MPa) when measured according to ISO 20795-2; (6) a Charpy impact 1 J value greater than 5 kJ / m 3 , greater than 8 kJ / m 3 , or greater than 10 kJ / m 3 (e.g., 5-25 kJ / m 3 , 5-20 kJ / m 3 , 8-25 kJ / m 3 , 8-20 kJ / m 3 , 10-25 kJ / m 3 , 10-20 kJ / m 3 , or 15-25 kJ / m 3 ) when measured according to ISO 179; and (7) an elongation at break greater than 8% or greater than 10% (e.g., 10-20%) when measured according to ISO 527 or ASTM D638 Type IV.

[0053] These and other embodiments are further illustrated in the following non-limiting examples. Examples

[0054] Table 1 provides formulations of polymerizable liquids according to some embodiments described herein. The amounts listed in Table 1 (and other composition / formulation tables below) are weight percentages based on the total weight of the polymerizable liquid. A dash (-) in the context of a composition / formulation table indicates that the component is not present, or in the context of a measured property table indicates that no measurement was made.

[0055] Table 2 provides physical properties of 3D articles printed using Formulations 1-5.

[0056] Table 3 provides formulations of polymerizable liquids according to some embodiments described herein.

[0057] Table 4 provides physical properties of 3D articles printed using Formulations 6-10.

[0058] Table 5 provides formulations of polymerizable liquids according to some embodiments described herein.

[0059] Table 6 provides physical properties of 3D articles printed using Formulations 11 and 12, including hydrolytic resistance properties when tested as described above.

[0060] Table 7 provides formulations of polymerizable liquids according to some embodiments described herein. In Table 7, the cyclomatable polymerization additive has the (structural) formula of Embodiment 6 below. Examples 14-16 are particularly preferred embodiments and can be compared to the non-preferred embodiment Example 13.

[0061] Table 8 provides physical properties of 3D articles printed using Formulations 13-16. In Table 8, stress relaxation values were measured according to ASTM D638 Type IV using dog bone samples (length x width x height = 50 mm x 21 mm x 0.76 mm) with a support span of 16 mm and a strain rate of 32 mm / min. The values were measured after the samples were soaked at 37 °C for at least 12 hours. The flexural strain was measured as 6*D*H / L 2 where L is the support span, H is the height or depth of the beam / sample under test, and D is the maximum deflection of the center of the beam / sample under test.

[0062] Table 9 provides formulations of polymerizable liquids according to some preferred embodiments described herein. In Table 9, the cyclomatable polymerization additive has the (structural) formula of Embodiment 6 below. Examples 17 and 18 are particularly preferred embodiments and can be compared to the non-preferred embodiment Example 19.

[0063] Table 10 provides physical properties of 3D articles printed using Formulations 17-19. In Table 10, stress relaxation values were measured as described above for Table 8.

[0064] Table 11 provides formulations of polymerizable liquids according to some additional preferred embodiments described herein.

[0065] Table 12 provides physical properties of 3D articles printed using Formulations 20-22. In Table 12, stress relaxation values were measured as described above for Table 8.

[0066] Some additional non-limiting example embodiments are further described below.

[0067] Embodiment 1. A polymerizable liquid comprising: at least one additive comprising a plurality of cyclizable polymeric functional groups separated by aliphatic linkers or oxyalkylene linkers, the cyclizable polymeric functional groups having the formula: .

[0068] Embodiment 2. The polymerizable liquid of Embodiment 1, wherein the additive is present in an amount of 5-40 weight percent based on the total weight of the polymerizable liquid.

[0069] Embodiment 3. The polymerizable liquid of Embodiment 1, wherein the additive is present in an amount of 5-30 weight percent, 7-30 weight percent, or 10-30 weight percent, or 10-20 weight percent based on the total weight of the polymerizable liquid.

[0070] Embodiment 4. The polymerizable liquid of any of the preceding embodiments, wherein the oxyalkylene linkers are oligomeric or polymeric.

[0071] Embodiment 5. The polymerizable liquid of any of the preceding embodiments, wherein the additive has the formula: wherein L is an aliphatic linker or an oxyalkylene linker.

[0072] Embodiment 6. The polymerizable liquid of any of the preceding embodiments, wherein the additive has the formula: wherein R 1 is hydrogen or an alkyl group, and m is an integer from 1 to 20.

[0073] Embodiment 7. The polymerizable liquid of any of the preceding embodiments, further comprising an oligomeric curable material, a monomeric curable material, or a mixture thereof.

[0074] Embodiment 8. The polymerizable liquid of Embodiment 7, comprising the oligomeric curable material in an amount of 5 to 50 weight percent, based on the total weight of the polymerizable liquid.

[0075] Embodiment 9. The polymerizable liquid of Embodiment 7, comprising the monomeric curable material in an amount of 10 to 70 weight percent, based on the total weight of the polymerizable liquid.

[0076] Embodiment 10. The polymerizable liquid of Embodiment 7, comprising the oligomeric curable material in an amount of 5 to 50 weight percent, based on the total weight of the polymerizable liquid, and the monomeric curable material in an amount of 10 to 70 weight percent, based on the total weight of the polymerizable liquid.

[0077] Embodiment 11. The polymerizable liquid of any of Embodiments 7-10, wherein the oligomeric curable material comprises an acrylate oligomer, a methacrylate oligomer, or a mixture thereof.

[0078] Embodiment 12. The polymerizable liquid of any of Embodiments 7-11, wherein the monomeric curable material comprises an acrylate monomer, a methacrylate monomer, or a mixture thereof.

[0079] Embodiment 13. The polymerizable liquid of Embodiment 12, wherein the acrylate monomer comprises a cyclic carbonate (meth)acrylate monomer.

[0080] Embodiment 14. The polymerizable liquid of Embodiment 13, wherein the cyclic carbonate (meth)acrylate monomer has the formula: wherein R1is a linear or branched C1-C6alkylene moiety; and wherein R2is H or CH3.

[0081] Embodiment 15. A method of printing a three-dimensional article, comprising: providing a polymerizable liquid according to any of Embodiments 1-14; and printing and photocuring the polymerizable liquid to form an article.

[0082] Embodiment 16. A polymerizable liquid, comprising: 15 to 35 weight percent of an oligomeric curable material; 35 to 75 weight percent of a monomeric curable material; and 10 to 20 weight percent of an additive comprising a plurality of cyclizable polymeric functional groups separated by aliphatic linkers or oxyalkylene linkers, wherein the cyclizable polymeric functional groups have the formula: , wherein is a point of attachment of the cyclizable polymeric functional group to the linker, and wherein the polymerizable liquid, when cured, has a stress relaxation / residual stress value in water at 37°C of greater than 1 N when measured in accordance with ASTM D638 Type IV, and optionally, wherein the polymerizable liquid, when cured, exhibits 1, 2, 3, 4, 5, or 6 additional structural features of the numbered list (1)-(7) described above immediately preceding the Examples section.

[0083] Embodiment 17. The polymerizable liquid of Embodiment 16, wherein the oligomeric curable material comprises one or more urethane (meth)acrylate oligomers.

[0084] Embodiment 18. The polymerizable liquid of Embodiment 16 or Embodiment 17, wherein the monomeric curable material comprises one or more (meth)acrylate species.

[0085] Embodiment 19. The polymerizable liquid of Embodiment 16 or Embodiment 17, wherein the monomeric curable material comprises at least one monofunctional (meth)acrylate and at least one multifunctional (meth)acrylate.

[0086] Embodiment 20. The polymerizable liquid of Embodiment 19, wherein the monomeric curable material comprises a monofunctional acrylate and a monofunctional methacrylate.

[0087] Embodiment 21. The polymerizable liquid of Embodiment 20, wherein: the monofunctional acrylate is present in the polymerizable liquid in an amount of 10-20 wt% or 20-30 wt%, based on the total weight of the polymerizable liquid; and the monofunctional methacrylate is present in the polymerizable liquid in an amount of 10-20 wt%.

[0088] Embodiment 22. The polymerizable liquid of Embodiment 19, wherein: the multifunctional (meth)acrylate comprises a di(meth)acrylate; and the di(meth)acrylate is present in the polymerizable liquid in an amount of 5-25 wt%, based on the total weight of the polymerizable liquid.

[0089] Embodiment 23. The polymerizable liquid of any one of Embodiments 16-22, wherein: the oligomeric curable material comprises one or more urethane (meth)acrylate oligomers; The monomeric curable material comprises monofunctional acrylates, monofunctional methacrylates and di(meth)acrylates, and optionally urethane acrylates; The monofunctional acrylates are present in the polymerizable liquid in an amount of 10-20 wt% or 20-30 wt%, based on the total weight of the polymerizable liquid; The monofunctional methacrylates are present in the polymerizable liquid in an amount of 10-20 wt%; and The di(meth)acrylates are present in the polymerizable liquid in an amount of 5-25 wt%, based on the total weight of the polymerizable liquid.

[0090] Embodiment 24. The polymerizable liquid of embodiment 23, wherein the additive has the following formula: wherein L is an aliphatic linker or an oxyalkylene linker.

[0091] Embodiment 25. The polymerizable liquid of embodiment 24, wherein the additive has the following formula: wherein R 1 is hydrogen or an alkyl group, and m is an integer from 1 to 20.

[0092] Embodiment 26. A method of printing a three-dimensional article, comprising: providing a polymerizable liquid according to any one of embodiments 16-25; and printing and photocuring the polymerizable liquid to form an article, wherein the polymerizable liquid, when cured, has a stress relaxation / residual stress value in water at 37°C of greater than 1 N when measured in accordance with ASTM D638 Type IV.

[0093] All patent documents mentioned herein are incorporated by reference in their entirety. In order to achieve various objects of the present application, various embodiments of the present application have been described. It should be appreciated that these embodiments are merely examples of the principles of the present application. Numerous improvements and modifications to the present application will be apparent to those skilled in the art without departing from the spirit and scope of the present application.

Claims

1. A method of printing a three-dimensional article, comprising: providing a polymerizable liquid comprising: 15-35 weight percent oligomeric curable material; 35-75 weight percent monomeric curable material; and 10-20 weight percent additive comprising a plurality of cyclizable polymeric functional groups separated by an aliphatic or oxyalkylene linker, wherein the cyclizable polymeric functional groups have the formula: ； and printing and photocuring the polymerizable liquid to form the article, wherein the polymerizable liquid, when cured, has a stress relaxation / residual stress value in water at 37°C greater than 1 N when measured in accordance with ASTM D638 Type IV.

2. The method of claim 1, wherein the oligomeric curable material comprises one or more urethane (meth)acrylate oligomers.

3. The method of claim 1, wherein the monomeric curable material comprises one or more (meth)acrylate species.

4. The method of claim 1, wherein the monomeric curable material comprises at least one monofunctional (meth)acrylate and at least one multifunctional (meth)acrylate.

5. The method of claim 4, wherein the monomeric curable material comprises a monofunctional acrylate and a monofunctional methacrylate.

6. The method of claim 5, wherein: the monofunctional acrylate is present in the polymerizable liquid in an amount of 20-30 weight percent, based on the total weight of the polymerizable liquid; and the monofunctional methacrylate is present in the polymerizable liquid in an amount of 10-20 weight percent.

7. The method of claim 4, wherein: the multifunctional (meth)acrylate comprises a di(meth)acrylate; and the di(meth)acrylate is present in the polymerizable liquid in an amount of 5-25 weight percent, based on the total weight of the polymerizable liquid.

8. The method of claim 1, wherein: the oligomeric curable material comprises one or more urethane (meth)acrylate oligomers; the monomeric curable material comprises a monofunctional acrylate, a monofunctional methacrylate, and a di(meth)acrylate; the monofunctional acrylate is present in the polymerizable liquid in an amount of 20-30 weight percent, based on the total weight of the polymerizable liquid; the monofunctional methacrylate is present in the polymerizable liquid in an amount of 10-20 weight percent; and the di(meth)acrylate is present in the polymerizable liquid in an amount of 5-25 weight percent, based on the total weight of the polymerizable liquid.

9. The method of claim 8, wherein the additive has the formula: wherein L is the aliphatic or oxyalkylene linker.

10. The method of claim 9, wherein the additive has the formula: wherein R 1 is hydrogen or alkyl, and m is an integer from 1 to 20.

11. A polymerizable liquid comprising: 15-35 weight percent oligomeric curable material; 35-75 weight percent monomeric curable material; and 10-20 weight percent additive comprising a plurality of cyclizable polymeric functional groups separated by an aliphatic or oxyalkylene linker, wherein the cyclizable polymeric functional groups have the formula: ， wherein is the point of attachment of the cyclizable polymerization functional group to the linker, and wherein the polymerizable liquid, when cured, has a stress relaxation / residual stress value in water at 37°C of greater than 1 N when measured according to ASTM D638 Type IV.

12. The polymerizable liquid of claim 11, wherein the oligomeric curable material comprises one or more urethane (meth)acrylate oligomers.

13. The polymerizable liquid of claim 11, wherein the monomeric curable material comprises one or more (meth)acrylate species.

14. The polymerizable liquid of claim 11, wherein the monomeric curable material comprises at least one monofunctional (meth)acrylate and at least one multifunctional (meth)acrylate.

15. The polymerizable liquid of claim 14, wherein the monomeric curable material comprises a monofunctional acrylate and a monofunctional methacrylate.

16. The polymerizable liquid of claim 15, wherein: the monofunctional acrylate is present in the polymerizable liquid in an amount of 20 to 30 percent by weight based on the total weight of the polymerizable liquid; and the monofunctional methacrylate is present in the polymerizable liquid in an amount of 10 to 20 percent by weight.

17. The polymerizable liquid of claim 14, wherein: the multifunctional (meth)acrylate comprises a di(meth)acrylate; and the di(meth)acrylate is present in the polymerizable liquid in an amount of 5 to 25 percent by weight based on the total weight of the polymerizable liquid.

18. The polymerizable liquid of claim 11, wherein: the oligomeric curable material comprises one or more urethane (meth)acrylate oligomers; the monomeric curable material comprises a monofunctional acrylate, a monofunctional methacrylate, and a di(meth)acrylate; the monofunctional acrylate is present in the polymerizable liquid in an amount of 20 to 30 percent by weight based on the total weight of the polymerizable liquid; the monofunctional methacrylate is present in the polymerizable liquid in an amount of 10 to 20 percent by weight; and the di(meth)acrylate is present in the polymerizable liquid in an amount of 5 to 25 percent by weight based on the total weight of the polymerizable liquid.

19. The polymerizable liquid of claim 18, wherein the additive has the following formula: wherein L is the aliphatic linker or oxyalkylene linker.

20. The polymerizable liquid of claim 19, wherein the additive has the following formula: wherein L is the aliphatic linker or oxyalkylene linker. wherein R 1 is hydrogen or alkyl, and m is an integer from 1 to 20.

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