CROSS REFERENCE TO RELATED APPLICATIONS [0001 ] This application claims priority pursuant to B5 U.S.C. § 1 1 9 to U.S. Provisional Patent Application No. 63/ 1 59,225, filed March 10, 2021 , which is hereby incorporated by reference in its entirety.

FIELD

[0002] The present invention relates to three-dimensional build materials and, in particular, to polymerizable liquids imparting flame resistant or flame retardant properties to articles printed from the polymerizable liquids.

BACKGROUND

[0003] 3D printers employ build materials, which are also known as inks, to form various 3D objects, articles, or parts in accordance with computer generated files. In some instances, the build material is solid at ambient temperatures and converts to liquid at elevated jetting temperatures. In other instances, the build material is liquid at ambient temperatures.

[0004] Build materials can comprise a variety of chemical species. Selection of chemical species to include in a build material can be selected according to various considerations including, but not limited to, desired chemical and/or mechanical properties of the printed article and operating parameters of the 3D printing apparatus. For example, ultra-violet (UV) curable acrylate formulations generally can print parts with high resolution on DLP systems. However, in many cases, the resulting parts lack desirable mechanical properties and can be prone to fracture or other degradative pathways. Such degradative pathways compromise article performance, leading to premature failure.

[0005] Additionally, some build materials and resultant articles printed from the build materials can be unsuitable for high temperature applications and/or other applications necessitating combustion resistance. As a result, BD printing technology may find limited application in fields requiring flame resistant or flame retardant materials and articles.

SUMMARY

[0006] In view of the foregoing, polymerizable liquids for BD printing applications are described herein which, in some embodiments, impart flame resistant and/or flame retardant properties to articles printed from the liquids. The polymerizable liquids may also impart desirable mechanical properties to the articles. In some embodiments, a polymerizable liquid comprises a curable isocyanurate component in an amount of at least 5 wt.%, based on total weight of the polymerizable liquid, and a brominated acrylate ester component. The brominated acrylate ester component can comprise one or more acrylate or methacrylate esters having bromine atoms bonded to aliphatic carbons.

[0007] In some embodiments, the polymerizable liquid further comprises an organophosphate component comprising one or more organophosphate compounds. In some embodiments, the polymerizable liquid further comprises an acrylate component. The acrylate component can comprise acrylate monomer, acrylate oligomer, or mixtures thereof.

[0008] Moreover, in some embodiments, the polymerizable liquid further comprises an additive of Formula I: wherein L and Z are ring substituents comprising at least one polymerizable point of unsaturation, and wherein R ¹ and R ² are independently selected from the group consisting of alkylene and alkenylene, and R ³ -R ⁶ each represent one to four optional ring substituents, each one of the one to four ring substituents independently selected from the group consisting of alkyl, heteroalkyl, haloalkyl, halo, hydroxyl, alkoxy, amine, amide, and ether, and wherein n is an integer from 1 to 7 or from 1 to 5. It is understood that hydrogen occupies positions on the aryl rings of Formula I in the absence of optional substituents R3-R6.

[0009] Additionally, methods of printing three-dimensional articles are described herein. A method, in some embodiments, comprises providing a polymerizable liquid comprising a curable isocyanurate component in an amount of at least 5 wt.% percent, based on total weight of the polymerizable liquid, and a brominated acrylate ester component. As detailed herein, the brominated acrylate ester component can comprise one or more acrylate or methacrylate esters having bromine atoms bonded to aliphatic carbons. The polymerizable liquid, in some embodiments, may also contain one or more of the organophosphate component, acrylate component, and/or additive of Formula I described herein.

[0010] The polymerizable liquid is printed and cured to form the article. In some embodiments, the article is formed via a layer-by-layer process, wherein layer formation is administered via deposition and curing of a layer of the polymerizable liquid.

[001 1] As described further herein, the polymerizable liquid may further comprise a photoinitiator component, and curing of the polymerizable liquid may occur by irradiation of the liquid with light of the appropriate wavelength to initial free radical polymerization.

[0012] These and other embodiments are further described in the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 illustrates additives of Formula I, according to some embodiments. DETAILED DESCRIPTION

[0014] Embodiments described herein can be understood more readily by reference to the following detailed description and examples. Elements, apparatus and methods described herein, however, are not limited to the specific embodiments presented in the detailed description and examples. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.

[001 5] In addition, 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 1 0.0” should be considered to include any and all subranges beginning with a minimum value of 1 .0 or more and ending with a maximum value of 1 0.0 or less, e.g., 1 .0 to 5.B, or 4.7 to 10.0, or B.6 to 7.9.

[0016] All ranges disclosed herein are also to be considered to include the end points of the range, unless expressly stated otherwise. For example, a range of “between 5 and 1 0” should generally be considered to include the end points 5 and 10.

[001 7] Further, when the phrase “up to” is used in connection with an amount or quantity, it is to be understood that the amount is at least a detectable amount or quantity. For example, a material present in an amount “up to” a specified amount can be present from a detectable amount and up to and including the specified amount.

[0018] 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, multijet modeling, and other additive manufacturing techniques now known in the art or that may be known in the future that use a build material or ink to fabricate three- dimensional objects.

[0019] Definitions:

The term “alkyl” as used herein, alone or in combination, refers to a straight or branched saturated hydrocarbon group optionally substituted with one or more substituents. For example, an alkyl can be Ci - CBO or Ci - Cis.

The term “alkenyl” as used herein, alone or in combination, refers to a straight or branched chain hydrocarbon group having at least one carbon- carbon double bond and optionally substituted with one or more substituents.

The term “alkynyl” as used herein, alone or in combination, refers to a straight or branched chain hydrocarbon group having at least one carbon- carbon triple bond and optionally substituted with one or more substituents.

The term “aryl” as used herein, alone or in combination, refers to an aromatic monocyclic or multicyclic ring system optionally substituted with one or more ring substituents. The term “heteroaryl” as used herein, alone or in combination, refers to an aromatic monocyclic or multicyclic ring system in which one or more of the ring atoms is an element other than carbon, such as nitrogen, boron, oxygen and/or sulfur.

The term “heterocycle” as used herein, alone or in combination, refers to a mono- or multicyclic ring system in which one or more atoms of the ring system is an element other than carbon, such as boron, nitrogen, oxygen, and/or sulfur or phosphorus and wherein the ring system is optionally substituted with one or more ring substituents. The heterocyclic ring system may include aromatic and/or non-aromatic rings, including rings with one or more points of unsaturation.

The term “heteroalkyl” as used herein, alone or in combination, refers to an alkyl moiety as defined above, having one or more carbon atoms, for example one, two or three carbon atoms, replaced with one or more heteroatoms, which may be the same or different.

The term “heteroalkenyl” as used herein, alone or in combination, refers to an alkyl moiety as defined above, having one or more carbon atoms, for example one, two or three carbon atoms, replaced with one or more heteroatoms, which may be the same or different.

The term “cycloalkyl” as used herein, alone or in combination, refers to a non-aromatic, mono- or multicyclic ring system optionally substituted with one or more ring substituents. [0020] In one aspect, polymerizable liquids for use in BD printing applications are described herein. The polymerizable liquids, for example, can be employed in DLP, SLA, and MJP printing applications, in some embodiments. A polymerizable liquid, in some embodiments, comprises a curable isocyanurate component in an amount of at least 5 wt.% based on total weight of the polymerizable liquid, and a brominated acrylate ester component.

[0021] Turning now to specific components, the curable isocyanurate component can comprise any curable isocyanurate not inconsistent with the technical objectives described herein. In some embodiments, the curable isocyanurate comprises one or a mixture of isocyanurate species.

[0022] Curable isocyanurates comprises at least one moiety or functionality operable to participate in the polymerization process. In some embodiments, the isocyanurate can comprise a plurality of polymerizable moieties or functionalities. A “polymerizable moiety,” for reference purposes herein, comprises a moiety that can be polymerized or cured to provide a printed BD article or object. Such polymerizing or curing can be carried out in any manner not inconsistent with the objectives of the present disclosure. Polymerizable moieties or functionalities can comprise those operable to undergo non- radiative induced polymerization mechanisms, including polycondensation or reaction between isocyanate and hydroxyl, for example. In some embodiments, the curable isocyanurate can comprise one or more reactive functionalities including, but not limited to, epoxy, amine, and thiol. Alternatively, one or more polymerizable functionalities can comprise one or more points of unsaturation suitable for free radical polymerization. The isocyanurate, in some embodiments, is an isocyanurate acrylate or isocyanurate polyacrylate. In some embodiments, an isocyanurate polyacrylate is of Formula II:

[0023] wherein R ^] -R ³ are independently selected from the group consisting of hydrogen and alkyl and m, n, and p are integers independently ranging from 1 to 10.

[0024] In some embodiments, the isocyanurate is an ally I isocyanurate, such as a polyallyl isocyanurate. A polyallyl isocyanurate, in some embodiments, is of Formula III:

wherein m, n, and p are integers independently ranging from 1 to 10.

[0025] In some embodiments, the curable isocyanurate is present in an amount of 30-80 wt.% or 35-70 wt.%, based on total weight of the polymerizable liquid.

[0026] In addition to the curable isocyanurate component, the polymerizable liquid comprises brominated acrylate ester component. The brominated acrylate ester component can comprise one or more acrylate or methacrylate esters having bromine atoms bonded to aliphatic carbons. In some embodiments, the brominated acrylate ester component comprises one or more compounds of the formula: wherein R ¹ is selected from the group consisting of hydrogen and methyl, and wherein R ² is selected from the groups consisting of brominated alkyl and brominated alkenyl. Brominated alkyl and brominated alkenyl groups are alkyl and alkenyl groups comprising one or more bromine substituents. In some embodiments, for example, the brominated acrylate ester component comprises trinol acrylate:

[0027] The brominated acrylate ester component can be present in the polymerizable liquid in any amount consistent with the technical objectives described herein of imparting flame resistance and/or flame retardant properties to articles printed from the polymerizable liquids in a BD printing apparatus. The amount of brominated acrylate ester can be selected according to several considerations including, but not limited to, the desired flame resistant and mechanical properties of articles printed from the polymerizable liquid, and other species present in the polymerizable liquid, such as other flame retardant species. In some embodiments, brominated acrylate ester is present in an amount of 5-50 wt.%, 10-40 wt.%, or 15-B5 wt.%, based on total weight of the polymerizable liquid.

[0028] In some embodiments, polymerizable liquids further comprise organophosphate component in addition to the curable isocyanurate component and brominated acrylate ester component, the organophosphate component comprising one or more organophosphate compounds. Any organophosphate consistent with imparting flame resistant or flame retardant properties to polymerizable liquids and articles printed from the polymerizable liquids can be employed.

[0029] In some embodiments, the one or more organophosphate compounds fall under the formula: wherein R ^] -R ³ are independently selected from the group consisting of hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heteroalkyl, heteroalkenyl, heterocyclyl, aryl, and heteroaryl. In some embodiments, for example, the one or more organophosphate compounds comprise aryl phosphate or heteroaryl phosphate. Aryl phosphates, in some embodiments, can include triphenyl phosphate. Moreover, in some embodiments, the one or more phosphates comprise bis(organophospates). Bis(organophosphates) can include resorcinol bi s(d i phenyl phosphate), bisphenol A bis(d i phenyl phosphate) or mixtures thereof, in some embodiments.

[0030] Organophospate compounds of the polymerizable liquid, in some embodiments, are not halogenated. The organophosphate compounds, for example, are not halogenated with fluorine, chlorine, or bromine. Alternatively, the organophosphosphate compounds are halogenated with fluorine, chlorine, bromine, or combinations thereof. In some embodiments, for example, one or more of R ^] -R ³ in the organophosphate formula are halogenated, such as brominated.

[0031 ] The organophosphate component can be present in the polymerizable liquid in any desired amount. In some embodiments, the organophosphate component is present in an amount of 5-40 wt.% or 10-30 wt.% based on total weight of the polymerizable liquid.

[0032] As described herein, the polymerizable liquid can further comprise an acrylate component in addition to the curable isocyanurate and brominated acrylate ester component. The acrylate component can comprise one or a mixture of light polymerizable acrylate species. In some embodiments, for example, the acrylate component can comprise acrylate monomer, acrylate oligomer, or mixtures thereof. As known to the skilled artisan, a monomer is a single structural unit of a polymer or copolymer and is not an oligomer or polymer. In contrast, an oligomer comprises a plurality of chemically linked monomers. In some embodiments, the acrylate component can comprise monofunctional acrylates, difunctional acrylates, or mixtures thereof. In some embodiments, for instance, the acrylate component 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- or 3 -hydroxy propyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate,

2- or B-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 mixtures thereof. In some embodiments, the acrylate component comprises a monofunctional or difunctional aliphatic urethane (meth)acrylate, or a monofunctional or difunctional polyether urethane (meth)acrylate.

[00BB] The acrylate component, in some embodiments, can comprise one or more of allyl acrylate, allyl methacrylate, triethylene glycol di(meth)acrylate, tricyclodecane dimethanol diacrylate, and cyclohexane dimethanol diacrylate. Additionally, in some embodiments, the acrylate component comprises diacrylate and/or dimethacrylate esters of aliphatic, cycloaliphatic or aromatic diols, including 1 ,3- or 1 ,4-butanediol, neopentyl glycol, 1 ,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, tripropylene glycol, ethoxylated or propoxylated neopentyl glycol, 1 ,4- dihydroxymethylcyclohexane, 2,2-bis(4-hydroxycyclohexyl)propane or bis(4- hydroxycyclohexyl)methane, hydroquinone, 4,4'-dihydroxybiphenyl, bisphenol A, bisphenol F, bisphenol S, ethoxylated or propoxylated bisphenol A, ethoxylated or propoxylated bisphenol F or ethoxylated or propoxylated bisphenol S. [00B4] Additional non-limiting examples of species suitable for inclusion in the acrylate component comprise the following: isobornyl acrylate (IBOA), commercially available from SARTOMER under the trade name SR 506A; difunctional acrylate commercially available from SARTOMER under the SR 8BBS trade designation; trifunctional acrylate monomer commercially available from SARTOMER under the SR 533 trade designation; isobornyl methacrylate, commercially available from SARTOMER under the trade name SR 423A; alkoxylated tetrahydrofurfuryl acrylate, commercially available from SARTOMER under the trade name SR 61 1 ; monofunctional urethane acrylate, commercially available from RAHN USA under the trade name GENOMER 1 122; aliphatic urethane diacrylate, commercially available from ALLNEX under the trade name EBECRYL 8402; difunctional aliphatic urethane (meth)acrylate, commercially available from DYMAX under the BR-952 trade designation; triethylene glycol diacrylate, commercially available from SARTOMER under the trade name SR 272; and triethylene glycol dimethacrylate, commercially available from SARTOMER under the trade name SR 205. Other commercially available curable components may also be used. In addition, in some cases, a monofunctional or difunctional acrylate comprises an aliphatic polyester urethane acrylate oligomer, a urethane (meth)acrylate resin, and/or an acrylate amine oligomeric resin, such as EBECRYL 7100. In some embodiments, the acrylate component comprises one or more acrylate derivatives such as acryloylmorpholine. [00B5] In addition to the monofunctional and difunctional acrylate species components described above, it is also possible, in some cases, to include trifunctional or higher functional acrylate species in a polymerizable liquid described herein. For example, in some instances, one or more tri(meth)acrylates may be used. However, it is to be understood that the functionality (i.e., mono-, d i- , tri- , or higher functionality) and the molecular weight of the acrylate species described herein can be selected to provide a build material having a viscosity suitable for use in a desired BD printing system. Non-limiting examples of trifunctional or higher (meth)acrylates that may be suitable for use in some embodiments described herein include 1 ,1 - trimethylolpropane tri(meth)acrylate, ethoxylated or propoxylated 1 ,1 ,1 — trimethylolpropanetri(meth)acrylate, ethoxylated or propoxylated glycerol tri(meth)acrylate, pentaerythritol monohydroxy tri(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate, bis(trimethylolpropane) and tetra(meth)acrylate.

[0036] The acrylate component can be present in the polymerizable liquid in any amount consistent with the objectives described herein. In some embodiments, the acrylate component is present in an amount in an amount up to about 80 wt. %. For example, the acrylate component can be present in an amount of 30-70 wt.%, or 40-60 wt.% based on total weight of the polymerizable liquid. [00B7] As described herein, the polymerizable liquid can further comprise an additive of Formula I: wherein L and Z are ring substituents comprising at least one polymerizable point of unsaturation, and wherein R ¹ and R ² are independently selected from the group consisting of alkylene and alkenylene, and R ³ -R ⁶ each represent one to four optional ring substituents, each one of the one to four ring substituents independently selected from the group consisting of alkyl, heteroalkyl, haloalkyl, halo, hydroxyl, alkoxy, amine, amide, and ether, and wherein n is an integer from 1 to 7 or from 1 to 5. It is understood that hydrogen occupies positions on the aryl rings of Formula I in the absence of optional substituents R3-R6.

[0038] In certain implementations, one or both of the alkylene or alkenylene moieties R ¹ and/or R ² can have a carbon chain length of 1 -8 carbon atoms, such as 1 -5 carbon atoms, 1 -3 carbon atoms, or 4-5 carbon atoms. In some embodiments, R ¹ and/or R ² comprises a Cl -Cl 0, Cl -C8, or Cl -C5 alkylene or alkenylene, where a “Cn” species (e.g., alkylene or alkenylene) includes exactly “n” carbon atoms in the species (e.g., a “C5” species contains exactly 5 carbon atoms). [00B9] As used herein, an alkylene moiety is a linear or branched saturated hydrocarbon moiety, such as an “ethylene” (-CH2CH2-) moiety. An alkenylene moiety is a linear or branched hydrocarbon moiety that includes one unsaturated carbon-carbon bond, such as a “propenylene” (-CH2CF CH-) moiety.

[0040] In some embodiments, L and Z comprise one or more moieties or functional groups independently selected from the group consisting of vinyl, vinyl ether, allyl, acrylate, and methacrylate. Moreover, in some embodiments, L and/or Z can comprise a cyclopolymerizable moiety or functional group. For example, L and/or may comprise a cyclopolymerizable moiety or functionality of the formula: where ΆLA is an attachment point of the cyclopolymerizable moiety or functionality to the compound of Formula I. In some embodiments, a compound of Formula I has a structure illustrated in FIG. 1 .

[0041] One or more additives of Formula I can be present in a polymerizable liquid in any desired amount. Amount of an additive of Formula I in the polymerizable liquid can be selected according to several considerations including, but not limited to, desired mechanical properties and/or flame resistant properties of articles printed from the polymerizable liquid, and chemical identities and/or amounts of other species in the polymerizable liquid. In some embodiments, one or more additives of Formula I are present in a polymerizable liquid in a total amount of 5 to 40 wt.% or 10 to BO wt%., based on total weight of the polymerizable liquid.

[0042] As detailed in the examples hereinbelow, the isocyanurate component, brominated acrylate ester component, organophosphate component, acrylate component and/or additive(s) of Formula I can be present in any combination and/or any amounts.

[0043] A polymerizable liquid described herein, in some embodiments, can further comprise a photoinitiator component for initiating polymerization of one or more components of the liquid upon exposure to light of the proper wavelength. In some embodiments, the photoinitiator component can initiate polymerization of the isocyanurate comprising one or more moieties polymerizable via free radical mechanisms, such as the isocyanurate acrylate. Similarly, a photoinitiator can be employed to polymerize the acrylate component. In some embodiments, the curable isocyanurate can be copolymerized with the acrylate component. In other embodiments, the curable isocyanurate and acrylate component are polymerized independently. [0044] Any photoinitiator not inconsistent with the objectives of the present disclosure can be used. In some embodiments, a photoinitiator comprises an alpha-cleavage type (unimolecular decomposition process) photoinitiator or a hydrogen abstraction photosensitizer-tertiary amine synergist, operable to absorb light preferably between about 250 nm and about 420 nm or between about 300 nm and about B85 nm, to yield free radical(s).

[0045] Examples of alpha cleavage photoinitiators are Irgacure 184 (CAS 947- 19-3), Irgacure 369 (CAS 1 19313-12-1 ), and Irgacure 819 (CAS 162881 -26-7). An example of a photosensitizer-amine combination is Darocur BP (CAS 1 19- 61 -9) with diethylaminoethylmethacrylate.

[0046] In addition, in some instances, suitable photoinitiators comprise benzoins, including 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-amylanthraquinone, triphenylphosphine, 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-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.

[0047] Suitable photoinitiators can also comprise those operable for use with a HeCd laser radiation source, 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). Additionally, in some cases, suitable photoinitiators comprise those operable for use with an Ar laser radiation source including benzil ketals, such as benzil dimethyl ketal. In some embodiments, a photoinitiator comprises an cx-hydroxyphenyl ketone, benzil dimethyl ketal or 2,4,6-trimethylbenzoyldiphenylphosphine oxide or a mixture thereof.

[0048] Another class of suitable photoinitiators, in some instances, comprises ionic dye-counter ion compounds capable of absorbing actinic radiation and generating free radicals for polymerization initiation. In some embodiments, polymerizable liquids containing ionic dye-counter ion compounds can be polymerized upon exposure to visible light within the adjustable wavelength range of about 400 nm to about 700 nm. Ionic dye-counter ion compounds and their mode of operation are disclosed in EP-A-0 22B 587 and U.S. Pat. Nos. 4,751 ,102; 4,772,530; and 4,772,541 .

[0049] A photoinitiator can be present in a polymerizable liquid described herein in any amount not inconsistent with the objectives of the present disclosure. In some embodiments, a photoinitiator is present in an amount of up to about 5 wt. %, based on the total weight of the polymerizable liquid. In some cases, a photoinitiator is present in an amount ranging from about 0.1 wt. % to about 5 wt. %.

[0050] Moreover, in some embodiments, a polymerizable liquid described herein can further comprise one or more sensitizers. A sensitizer can be added to increase the effectiveness of one or more photoinitiators that may also be present. Any sensitizer not inconsistent with the objectives of the present disclosure may be used. In some cases, a sensitizer comprises isopropylthioxanthone (ITX) or 2-chlorothioxanthone (CTX).

[0051] A sensitizer can be present in the polymerizable liquid in any amount not inconsistent with the objectives of the present disclosure. In some embodiments, a sensitizer is present in an amount ranging from about 0.1 wt. % to about 2 wt. % or from about 0.5 wt. % to about 1 wt. %, based on the total weight of the polymerizable liquid.

[0052] In some embodiments, one or more UV-absorbers and/or light stabilizers can be present in the polymerizable liquid. In some embodiments, for example, one or more UV-absorbers and/or light stabilizers can be present in an amount of 0.1 -2 wt.%, based on the total weight of the polymerizable liquid. In some embodiments, UV-absorbers and/or light stabilizers are commercially available from BASF of Florham Park, New Jersey under the TINUVIN ^® trade-designation. [005B] In another aspect, methods of printing a BD article or object are described herein. Methods of printing a 3D article or object can include forming the 3D article from a plurality of layers of a polymerizable liquid described herein in a layer-by-layer manner. Any polymerizable liquid or component described herein may be used in the fabrication of the article by additive manufacturing.

[0054] A method, in some embodiments, comprises providing a polymerizable liquid comprising a curable isocyanurate component in an amount of at least 20 wt.% percent, based on total weight of the polymerizable liquid, and an organophosphate component comprising one or more organophosphate compounds. The polymerizable liquid is printed and cured to form the article.

In some embodiments, the polymerizable liquid also comprises an acrylate component. The acrylate component can comprise acrylate monomer, acrylate oligomer, or mixtures thereof.

[0055] As described further herein, the polymerizable liquid may further comprise a photoinitiator component, and curing of the polymerizable liquid may occur by irradiation of the liquid with light of the appropriate wavelength to initial free radical polymerization.

[0056] In some embodiments, layers of polymerizable liquids can be deposited according to an image of the 3D article in a computer readable format during formation of the three-dimensional article. The polymerizable liquid can be deposited according to preselected computer aided design (CAD) parameters. Moreover, in some cases, one or more layers of the polymerizable liquid described herein has a thickness of about 10 pm to about 100 pm, about 10 pm to about 80 pm, about 10 pm to about 50 pm, about 20 pm to about 100 pm, about 20 pm to about 80 pm, or about 20 pm to about 40 pm. Other thicknesses are also possible.

[0057] Additionally, it is to be understood that methods of printing a BD article described herein can include so-called “multi-jet” or “stereolithography” BD printing methods. For example, in some instances, a multi-jet method of printing a 3D article comprises selectively depositing layers of a polymerizable liquid described herein onto a substrate, such as a build pad of a 3D printing system. In addition, in some embodiments, a method described herein further comprises supporting at least one of the layers of the polymerizable liquid with a support material. Any support material not inconsistent with the objectives of the present disclosure may be used.

[0058] 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 comprises retaining the polymerizable liquid in a container and selectively applying energy to the polymerizable liquid in the container to solidify at least a portion of a polymerizable liquid, thereby forming a solidified layer that defines a cross-section of the 3D article. Additionally, a method described herein can further comprise raising or lowering the solidified layer to provide a new or second layer of polymerizable liquid, followed by again selectively applying energy to the polymerizable liquid in the container to solidify at least a portion of the new or second polymerizable liquid that defines a second cross-section of the BD article. Further, the first and second cross-sections of the BD article can be bonded or adhered to one another in the z-direction (or build direction corresponding to the direction of raising or lowering recited above) by the application of the energy for solidifying the polymerizable liquid. Moreover, selectively applying energy to the polymerizable liquid in the container can comprise applying electromagnetic radiation, such as UV and/or visible radiation, having a sufficient energy to initiate polymerization of the polymerizable material as described herein. In addition, in some cases, raising or lowering a solidified layer of polymerizable liquid is carried out using an elevator platform disposed in the container of fluid build material. A method described herein can also comprise planarizing a new layer of polymerizable liquid provided by raising or lowering an elevator platform. Such planarization can be carried out, in some cases, by a wiper or roller.

[0059] Articles printed according to methods described herein can exhibit one or more desirable mechanical properties. 3D articles printed from polymerizable liquids described herein may display a tensile modulus of at 2700-3200 MPa, in some embodiments. Values for tensile strength and tensile modulus provided herein can be determined according to ASTM D638. Additionally, 3D articles printed from polymerizable liquids described herein can exhibit a HDT of at least 100°C, such as 100-1 S0°C. HDT is measured using DMA at 0.455 MPa according to ASTM D648.

[0060] Articles printed according to methods described herein can also exhibit desirable flame resistant and/or flame retardant properties. In some embodiments, articles printed according to methods described herein exhibit a vO rating under Flammability UL 94V. Testing sample thickness achieving a vO rating can be less than 2 mm or less than 1 mm, such as 0.8 mm or 0.4 mm, in some embodiments.

[0061] These foregoing embodiments are further illustrated in the following non-limiting examples.

EXAMPLES

[0062] Table 1 provides a formulation of a polymerizable liquid according to some embodiments described herein.

Table I - Polymerizable Liquids

[0063] Properties of articles formed of the polymerizable liquids of Samples 1 -6 are provided in Table II. Flammability testing was conducted in accordance with UL 94V and employed samples of 0.8 mm in thickness.

Table II - Article Properties

[0064] Some additional, non-limiting example embodiments are further described below.

[0065] Embodiment 1. A polymerizable liquid comprising: a curable isocyanurate component in an amount of at least 5 wt.%, based on total weight of the polymerizable liquid; and a brominated acrylate ester component. [0066] Embodiment 2. The polymerizable liquid of Embodiment 1 , wherein the curable isocyanurate component is polymerizable via free radical polymerization.

[0067] Embodiment B. The polymerizable liquid of Embodiment 2, wherein the curable isocyanurate component comprises isocyanurate polyacrylate, polyallyl isocyanurate, or mixture thereof.

[0068] Embodiment 4. The polymerizable liquid of Embodiment S, wherein the isocyanurate polyacrylate is of Formula II: wherein R ^] -R ³ are independently selected from the group consisting of hydrogen and alkyl and m, n, and p are integers independently ranging from 1 to 10.

[0069] Embodiment 5. The polymerizable liquid of Embodiment S, wherein the polyallyl isocyanurate is of Formula III: wherein m, n, and p are integers independently ranging from 1 to 10.

[0070] Embodiment 6. The polymerizable liquid of any of Embodiments 1 -5, wherein the brominated acrylate ester component comprises one or more compounds of the formula: wherein R ¹ is selected from the group consisting of hydrogen and methyl, and wherein R ² is selected from the groups consisting of brominated alkyl and brominated alkenyl.

[0071 ] Embodiment 7. The polymerizable liquid of Embodiment 6, wherein the brominated acrylate ester component comprises trinol acrylate.

[0072] Embodiment 8. The polymerizable liquid of any of Embodiments 1 -7, wherein the brominated acrylate ester component is present in an amount of 1 0-40 wt.%, based on total weight of the polymerizable liquid. [007B] Embodiment 9. The polymerizable liquid of any of Embodiments 1 -8, wherein the polymerizable liquid further comprises an organophosphate component including one or more organophosphate compounds.

[0074] Embodiment 10. The polymerizable liquid of Embodiment 9, wherein the organophosphate component is present in an amount of 5-40 wt.%, based on total weight of the polymerizable liquid.

[0075] Embodiment 1 1 . The polymerizable liquid of Embodiment 9 or 10, wherein the one or more organophosphate compounds are of the formula: wherein R ^] -R ³ are independently selected from the group consisting of hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, heteroalkyl, heteroalkenyl, heterocyclyl, aryl, and heteroaryl.

[0076] Embodiment 1 2. The polymerizable liquid of Embodiment 9 or 10, wherein the one or more organophosphate compounds comprise bis(organophosphate).

[0077] Embodiment 1 B. The polymerizable liquid of any of Embodiments 1 - 1 2, wherein the curable isocyanurate component is present in an amount of 30-70 weight percent based on total weight of the polymerizable liquid. [0078] Embodiment 1 4. The polymerizable liquid of any of Embodiments 1 - 1 3 further comprising an acrylate component. [0079] Embodiment 15. The polymerizable liquid of Embodiment 14, wherein the acrylate component is present in an amount of 30-70 wt.% based on total weight of the polymerizable liquid.

[0080] Embodiment 16. The polymerizable liquid of Embodiment 14 or 15, wherein the acrylate component comprises a mixture of acrylate monomer and acrylate oligomer.

[0081] Embodiment s. The polymerizable liquid of any of Embodiments 1 - 16 further comprising an additive of Formula I: wherein L and Z are ring substituents comprising at least one polymerizable point of unsaturation, and wherein R ¹ and R ² are independently selected from the group consisting of alkylene and alkenylene, and R ³ -R ⁶ each represent one to four optional ring substituents, each one of the one to four ring substituents independently selected from the group consisting of alkyl, heteroalkyl, haloalkyl, halo, hydroxyl, alkoxy, amine, amide, and ether, and wherein n is an integer from 1 to 7.

[0082] Embodiment 18. The polymerizable liquid of Embodiment 17, wherein R ¹ and R ² are alkylene. [008B] Embodiment 19. The polymerizable liquid of Embodiment 17 or 18, wherein L and Z each comprise a moiety independently selected from the group consisting of vinyl, allyl, vinyl ether, acrylate, and methacrylate.

[0084] Embodiment 20. The polymerizable liquid of Embodiment 17 or 18, wherein L and Z each comprise a cyclopolymerizable functionality.

[0085] Embodiment 21 . The polymerizable liquid of Embodiment 20, wherein the cyclopolymerizable functionality is of the formula: where ΆAL is an attachment point of the cyclopolymerizable functionality to the compound of Formula I.

[0086] Embodiment 22. The polymerizable liquid of any of Embodiments 17-

21 , wherein n is 2 or B.

[0087] Embodiment 23. The polymerizable liquid of any of Embodiments 17-

22, wherein L and Z each comprise an acrylate moiety.

[0088] Embodiment 24. The polymerizable liquid of any of Embodiments 17- 22, wherein and L and Z each comprise a methacrylate moiety.

[0089] Embodiment 25. The polymerizable liquid of any of Embodiments 1 - 24 further comprising at least one of an organophosphate component, acrylate component, and an additive of Formula I: wherein L and Z are ring substituents comprising at least one polymerizable point of unsaturation, and wherein R ¹ and R ² are independently selected from the group consisting of alkylene and alkenylene, and R ³ -R ⁶ each represent one to four optional ring substituents, each one of the one to four ring substituents independently selected from the group consisting of alkyl, heteroalkyl, haloalkyl, halo, hydroxyl, alkoxy, amine, amide, and ether, and wherein n is an integer from 1 to 7.

[0090] Embodiment 26. The polymerizable liquid of any of Embodiments 1 - 25 further comprising a photoinitiator component.

[0091] Embodiment 27. The polymerizable liquid of Embodiment 26, wherein the photoinitiator component is present in an amount of 0.1 -5 weight percent based on total weight of the polymerizable liquid.

[0092] Embodiment 28. A method of printing a three-dimensional article comprising: providing a polymerizable liquid of any of Embodiments 1 to 27; and printing and curing the polymerizable liquid with light to form the article. [0093] Embodiment 29. The method of Embodiment 28, wherein the polymerizable liquid is provided in a layer-by-layer process. [0094] Embodiment BO. The method of Embodiment 28, wherein the polymerizable liquid further comprises a photoinitiator component and curing the polymerizable liquid proceeds via free radical polymerization.

[0095] Embodiment 31 . The method of Embodiment 28, wherein the article has a vO rating according to UL 94 V.

[0096] All patent documents referred to herein are incorporated by reference in their entireties. Various embodiments of the invention have been described in fulfillment of the various objectives of the invention. It should 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.