Silicone resin compositions and methods of using same

Abstract

Silicone resin compositions are provided that may be useful in additive manufacturing. Such resin compositions include: (a) at least one polyvinyl siloxane monomer and / or prepolymer; (b) at least one polymercapto siloxane monomer and / or prepolymer; and at least one photoinitiator. Also provided is an additive manufacturing resin composition, including: (i) about 0.5% by weight to about 10% or about 20% by weight of a polyvinyl silicone monomer and / or prepolymer; (ii) a polymercapto silicone monomer and / or prepolymer; (iii) a photoinitiator; (iv) optionally, a filler; and (v) optionally, a non-reactive diluent, wherein the non-reactive diluent has a boiling point of from about 80 or 100 °C to about 250 °C. Methods of making a three-dimensional (3D) object from a resin composition taught herein are also described, as well as a 3D object produced by such method.

Description

[0001] SILICONE RESIN COMPOSITIONS AND METHODS OF USING SAME

[0002] CROSS REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority from U.S. Provisional Application No. 63 / 611,895, filed December 19, 2023, the disclosure of which is hereby incorporated by reference in its entirety.

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to resins and methods of additive manufacturing. In particular, the present invention relates to silicone-based resins for use in additive manufacturing.

[0006] BACKGROUND OF THE INVENTION

[0007] A group of additive manufacturing techniques sometimes referred to as “stereolithography” creates a three-dimensional object by the sequential polymerization of a light polymerizable resin. Such techniques may be “bottom-up” techniques, where light is projected into the resin on the bottom of the growing object through a light transmissive window, or “top-down” techniques, where light is projected onto the resin on top of the growing object, which is then immersed downward into the pool of resin.

[0008] The introduction of a more rapid stereolithography technique known as continuous liquid interface production (CLIP) has expanded the usefulness of stereolithography from prototyping to manufacturing. See, e.g., U.S. Pat. Nos. 9,211,678, 9,205,601, and 9,216,546; and also J. Tumbleston, D. Shirvanyants, N. Ermoshkin et al., Continuous liquid interface production of 3D Objects, Science 347, 1349-1352 (2015).

[0009] Additive manufacturing techniques that employ liquid resins that harden via exposure to UV or visible light (often called “VAT” 3D printing) are reliant on low viscosity resins to print quickly. These techniques include both “top-down” and “bottom-up” versions of stereolithography (SLA), digital light processing (DLP), CLIP, and digital light synthesis (DLS), among others. Low viscosity resins minimize viscous forces due to the intimate contact between the build plate / growing 3D printed article and the window. Lower viscosities also allow resin reflow to occur within shorter timescales. Contrary to the process benefits afforded by lower resin viscosity, polymerization / cross-linking of pre-polymers with higher starting molecular weights (and therefore higher starting viscosities) often results in final articles having more desirable mechanical properties, such as better durability, extensibility, toughness, ultimate tensile strength, and fatigue resistance. This trade-off between viscosity and mechanical durability is especially true in silicone materials, which are often highly filled with silica or other inorganic materials.

[0010] It would be desirable to have the benefits of a low viscosity resin while also being able to incorporate prepolymer starting materials, particularly silicone prepolymers, in order to achieve desirable properties in the final additively manufactured objects.

[0011] SUMMARY OF THE INVENTION

[0012] Provided according to some embodiments of the invention are silicone resin compositions that may be useful in additive manufacturing. Such resin compositions include: (a) at least one polyvinyl siloxane monomer and / or prepolymer; (b) at least one polymercapto siloxane monomer and / or prepolymer; and at least one photoinitiator. The type of polyvinyl siloxane monomers and / or prepolymers and polymercapto siloxane monomers and / or prepolymers may vary based on the type of resin composition, as described in further detail below.

[0013] In some embodiments, an additive manufacturing resin composition may include: (i) a polyvinyl silicone monomer and / or prepolymer (e.g., a divinyl silicone prepolymer having a molecular weight (Mn) in a range of 5 kDa to 300 kDa); (ii) a polymercapto silicone monomer and / or prepolymer (e.g., a polymercapto silicone prepolymer having a molecular weight (Mn) in a range of 500 Da to 10 kDa); (iii) a photoinitiator; and (iv) a non-reactive diluent, wherein the non-reactive diluent has a boiling point of from about 80 or 100 °C to about 250 °C.

[0014] In some embodiments, the resin composition has a viscosity in a range of about 500 or 1000 centipoise (cP) to about 50,000 or 100,000 cP.

[0015] In some embodiments, the non-reactive diluent is present in an amount of from about 5 percent by weight to about 50 percent by weight (e.g., about 5 percent by weight to about 20 percent by weight).

[0016] In some embodiments, the non-reactive diluent comprises an alkane (e.g., a C7-C15 alkane) and / or a volatile silicone diluent. In some embodiments, the non-reactive diluent comprises an acetate (e.g., a C3-C9 acetate).

[0017] In some embodiments, the resin composition further comprises at least one additional component selected from the group consisting of a radical inhibitor; a UV absorber (e.g., a pigment and / or dye); an antioxidant; a plasticizer; a filler; and a thermal inhibitor. In some embodiments, the polyvinyl silicone monomer and / or prepolymer is present at a concentration in a range of about 25 weight percent to about 99 weight percent (e.g., about 50 weight percent to about 90 weight percent); the polymercapto silicone monomer and / or prepolymer is present at a concentration in a range of 0.5 weight percent to 20 weight percent (e.g., about 2 weight percent to about 15 weight percent); the non-reactive diluent is present at a concentration in a range of about 5 weight percent to about 50 weight percent (e.g., about 5 weight percent to about 20 weight percent); and the filler is present at a concentration in a range of about 2 weight percent to 50 weight percent (e.g., about 5 weight percent to about 30 weight percent).

[0018] Also provided is a method of making a three-dimensional (3D) object from a light polymerizable resin (e.g., via bottom-up stereolithography), including the steps of: (a) providing the additive manufacturing resin composition as described herein; (b) producing the 3D object from the resin composition by reacting the polyvinyl silicone monomers and / or prepolymers and the polymercapto silicone monomers and / or prepolymers; (c) optionally cleaning the 3D object; and then (d) heating the 3D object (e.g., at a temperature in a range of about 70 °C to about 200 °C) to volatilize and remove (e.g., partially, substantially, or completely remove) the non-reactive diluent.

[0019] In some embodiments, producing step (b) comprises providing a digital model of the 3D object; applying an iso-tropic volumetric scale factor to the 3D object sufficient to offset volumetric shrinkage due to solvent removal to produce a modified digital model; and then producing the 3D object using the modified digital model.

[0020] In some embodiments, the heating step is carried out with the 3D object in an inert atmosphere.

[0021] In some embodiments, the method further includes: concurrently with the heating step, condensing volatilized non-reactive diluent in an amount sufficient to reduce the duration of the heating step.

[0022] Further provided according to some embodiments is an additive manufacturing resin composition, including: (i) about 0.5% by weight to about 10% or about 20% by weight of a polyvinyl silicone monomer and / or prepolymer (e.g., a polyvinyl silicone monomer and / or prepolymer having three or more vinyl groups per molecule, or on average more than 2 vinyl groups per molecule), optionally wherein the polyvinyl silicone monomer and / or prepolymer has a molecular weight (Mn) in a range of about 500 g / mol to about 10,000 g / mol; (ii) a polymercapto silicone monomer and / or prepolymer (e.g., a dimercapto silicone monomer and / or prepolymer having terminal thiol functional groups), optionally wherein the polymercapto silicone monomer and / or prepolymer has a molecular weight (Mn) in a range of about 5000 g / mol to about 300,000 g / mol; (iii) a photoinitiator; (iv) optionally, a filler; and (v) optionally, a non-reactive diluent, wherein the non-reactive diluent has a boiling point of from about 80 or 100 °C to about 250 °C.

[0023] In some embodiments, the polymercapto silicone monomer and / or prepolymer is present at a concentration in a range of about 25 weight percent to about 99 weight percent (e.g., in a range of about 50 weight percent to about 90 weight percent).

[0024] In some embodiments, the resin composition further includes at least one additional component selected from the group consisting of an antioxidant, a plasticizer, a radical inhibitor, a UV absorber (e.g., a pigment and / or dye), a filler, and a thermal inhibitor.

[0025] In some embodiments, the polyvinyl silicone monomer and / or prepolymer is present at a concentration in a range of about 0.5 weight percent to about 20 weight percent (e.g., in a range of about 2 weight percent to about 15 weight percent); the polymercapto silicone monomer and / or prepolymer is present at a concentration in a range of about 25 weight percent to about 99 weight percent (e.g., in a range of about 50 weight percent to about 90 weight percent); and the filler is present at a concentration in a range of about 2 weight percent to about 50 weight percent (e.g., in a range of about 5 weight percent to about 30 weight percent).

[0026] Also provided is a method of making a three-dimensional (3D) object from a light polymerizable resin (e.g., via bottom-up stereolithography), including the steps of: (a) providing an additive manufacturing resin composition as described herein; (b) producing the 3D object from the resin composition by reacting the polyvinyl silicone monomers and / or prepolymers and the polymercapto silicone monomers and / or prepolymers; (c) optionally cleaning the 3D object; and then (d) optionally heating the 3D object (e.g., at a temperature in a range of about 70 °C to about 200 °C) to volatilize and remove (e.g., partially, substantially, or completely remove) the non-reactive diluent when present.

[0027] In some embodiments, producing step (b) comprises providing a digital model of the 3D object; applying an iso-tropic volumetric scale factor to the 3D object sufficient to offset volumetric shrinkage due to solvent removal to produce a modified digital model; and then producing the 3D object using the modified digital model.

[0028] Further provided is a 3D object produced by a method as described herein.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 presents a schematic of a system useful in the present invention, and includes a user interface 3 for inputting instructions, a controller 4, and an additive manufacturing apparatus 5. The controller 4 may include at least one processor 4a, a volatile (or “working”) memory 4b, such as random-access memory, and at least one non-volatile or persistent memory 4c, such as a hard drive or a flash drive.

[0031] FIG. 2 is a graph plotting the stress-strain curves for example formulations described herein.

[0032] DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0033] The present invention is now described more fully hereinafter with reference to particular embodiments. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.

[0034] The terminology used herein is for the purpose of describing the particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include plural forms as well, unless the context clearly indicates otherwise.

[0035] It will be further understood that the terms “comprises” or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements components and / or groups or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups or combinations thereof. The sequence of operations (or steps) is not limited to the order presented in the claims or figures unless specifically indicated otherwise. Any element that comprises certain features, integers, steps, operations, elements, components and / or groups may also “consist of’ or “consist essentially of’ such features, integers, steps, operations, elements, components and / or groups, respectively.

[0036] As used herein, the term “and / or” includes any and all possible combinations of one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative (“or”).

[0037] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and claims and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. It will be understood that, although the terms first, second, etc. (or the use of “additional”) may be used herein to describe various elements or components, these elements and components should not be limited by these terms. Rather, these terms are only used to distinguish one element or component from another element or component. Thus, a first element or component could be termed a second element or component without departing from the teachings of the present invention.

[0038] All publications and patents cited herein are specifically incorporated by reference to disclose the methods and / or materials with which the documents are cited.

[0039] As used herein, the term “about” with reference to a numerical number or range refers to the exact numbers and to values that are + / - 1%, 2%, 5%, or 10% thereof. It is also to be understood that where a range of values is provided, each intervening integer within the upper and lower limit of the range is also explicitly disclosed.

[0040] Provided according to some embodiments of the invention are silicone resin compositions that may be useful in additive manufacturing. Such resin compositions include (a) at least one polyvinyl siloxane monomer and / or prepolymer; (b) at least one polymercapto siloxane monomer and / or prepolymer; and at least one photoinitiator. The type of polyvinyl siloxane monomers and / or prepolymers and polymercapto siloxane monomers and / or prepolymers may vary based on the type of resin composition, as described in further detail below.

[0041] Polyvinyl Silicone Monomer and / or Prepolymer

[0042] The silicone resin compositions of the invention include at least one polyvinyl silicone monomer and / or prepolymer. The term “polyvinyl silicone monomer and / or prepolymer” (also referred to herein as a “polyvinyl silicone”), as used herein, refers to a monomer, oligomer, polymer, or any combination thereof, that includes at least one siloxane linkage (e.g., 2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 1000, 2000, 3000, or a range defined between any two of the foregoing values) and at least two vinyl groups (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, and any range defined between any of the foregoing values). The number of siloxane linkages and / or vinyl groups may vary within a resin composition. Thus, in some embodiments, the average number of siloxane linkages and / or vinyl groups may be a noninteger within the aforementioned ranges.

[0043] In some embodiments, the polyvinyl silicone includes at least one siloxane monomeric unit, organosiloxane monomeric unit, or a combination thereof. In some embodiments, the polyvinyl silicone includes monomeric units of silicon atoms having one, two, three, or four oxygen linkages thereto (i.e., M, D, T, or Q monomeric units), including combinations thereof. For example, in some embodiments, the polyvinyl siloxane is a MM resin, an MD resin, a DT resin, an MT resin, an MDT resin, a DTQ resin, an MTQ resin, an MDTQ resin, a DQ resin, an MQ resin, a DTQ resin, an MTQ resin, an MDQ resin, or a polyhedral oligomeric silsesquioxane (POSS) resin.

[0044] In some embodiments, the silicone portion of a polyvinyl silicone is a linear polydimethylsiloxane (PDMS). In some embodiments, the polyvinyl silicone is a divinyl silicone. In some embodiments, the polyvinyl silicone is an end-capped divinyl PDMS (a PDMS linear chain with a vinyl group at each terminus).

[0045] Polymercapto Silicone Monomer and / or Prepolymer

[0046] The silicone resin compositions of the invention include at least one polymercapto silicone monomer and / or prepolymer. The term “polymercapto silicone monomer and / or prepolymer” (also referred to herein as a “polymercapto silicone”), as used herein, refers to a monomer, oligomer, polymer, or any combination thereof, that includes at least one siloxane linkage (e.g., 2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 1000, 2000, 3000, or a range defined between any two of the foregoing values) and at least two thiol groups (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, and any range defined between any of the foregoing values). The number of siloxane linkages and / or thiol groups may vary within a resin composition. Thus, in some embodiments, the average number of siloxane linkages and / or thiol groups may be a non-integer within the aforementioned ranges.

[0047] In some embodiments, the polymercapto silicone includes at least one of a siloxane monomeric unit, an organosiloxane monomeric unit, or a combination thereof. In some embodiments, the polymercapto silicone includes monomeric units of silicon atoms having one, two, three, or four oxygen linkages thereto (i.e., M, D, T, or Q monomeric units), including combinations thereof. For example, in some embodiments, the polyvinyl siloxane is a MM resin, an MD resin, a DT resin, an MT resin, an MDT resin, a DTQ resin, an MTQ resin, an MDTQ resin, a DQ resin, an MQ resin, a DTQ resin, an MTQ resin, an MDQ resin, or a polyhedral oligomeric silsesquioxane (POSS) resin.

[0048] In some embodiments, the silicone portion of a polymercapto silicone is a linear polydimethylsiloxane (PDMS). In some embodiments, the polymercapto silicone is a dithiol silicone. In some embodiments, the polymercapto silicone is an end-capped dithiol PDMS (a PDMS linear chain with a thiol group at each terminus). Photoinitiator

[0049] Any suitable photoinitiator may be included in resin compositions of the invention. In some embodiments, the photoinitiator is a free radical photoinitiator. “Free radical photoinitiator” as used herein includes type I free radical photoinitiators, such as phosphineoxide (TPO) or hydroxyacetophenone (HAP), and / or type II free radical photoinitiators, such as a benzophenone photoinitiator (optionally but preferably in combination with a co-initiator (e.g., an alcohol or amine)). Particular examples include, but are not limited to, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), diphenylphosphinyl(2,4,6-trimethylphenyl)methanone; benzophenone; substituted benzophenones; acetophenone; substituted acetophenones; benzoin; benzoin alkyl esters; xanthone; substituted xanthones; diethoxy-acetophenone; benzoin methyl ether; benzoin ethyl ether; benzoin isopropyl ether; diethoxyxanthone; chloro-thio-xanthone; N-methyl diethanol- amine-benzophenone; 2-hydroxy-2-m ethyl- 1 -phenyl-propan- 1 -one; 2-benzyl-2-

[0050] (dimethylamino)- 1 -[4-(4-morpholinyl)phenyl]- 1 -butanone; 2-isopropylthi oxanthone (ITX); and mixtures thereof. See, e.g., U.S. Pat. No. 9,090,765 for additional photoinitiator examples.

[0051] Resin Composition 1 : Resin Compositions Including Non-Reactive Diluent! s)

[0052] In some embodiments, resin compositions of the invention include a polyvinyl silicone monomer and / or prepolymer; a polymercapto silicone monomer and / or prepolymer; a photoinitiator; and a non-reactive diluent. In some embodiments, the non-reactive diluent has a boiling point of from about 80 or 100 °C to about 160, 200, 240 or 250 °C.

[0053] In some embodiments, the silicone portion of a polyvinyl silicone is a linear polydimethylsiloxane (PDMS). In some embodiments, the polyvinyl silicone is a divinyl silicone. In some embodiments, the polyvinyl silicone is an end-capped divinyl PDMS (a PDMS linear chain with a vinyl group at each terminus).

[0054] The molecular weight of the polyvinyl silicone may vary. However, in some embodiments, the polyvinyl silicone has a molecular weight (Mn) in a range of 5 kDa to 300 kDa (e.g., 30 kDa to 100 kDa). In some embodiments, the polyvinyl silicone is a prepolymer in a range of 30 kDa to 100 kDa and provides the primary elastic portion of the resulting crosslinked silicone polymer formed by the additive manufacturing process.

[0055] In some embodiments, in Resin Composition 1, the polymercapto silicone includes at least three thiol groups (and / or on average more than two thiol groups). In some embodiments, at least three of the thiol groups in the polymercapto silicone are present on a terminal and / or pendant portion of the siloxane chain. For example, in some embodiments, the polymercapto silicone is a linear silicone having multiple (3 or more) thiol groups pendant from the polysiloxane chain. In some embodiments, the polymercapto silicone has a molecular weight (Mn) in a range of about 500 Da to about 10 kDa (e.g., 2 kDa to 5 kDa). Thus, the polymercapto silicone monomer and / or prepolymer acts primarily as a crosslinker in the resulting silicone polymer thus formed.

[0056] Examples of suitable polymercapto silicones for use in the present invention include, but are not limited to: (mercaptopropyl)methylsiloxane-dimethylsiloxane copolymer (CAS #102783-03-9); thiol-terminated polydimethylsiloxane; thiolated polyhedral oligomeric silsesquioxane (POSS); and combinations thereof.

[0057] In some embodiments, for Resin Composition 1, the polyvinyl silicone and the polymercapto silicone are included in the resin composition in a vinyl to thiol ratio of from 1 :50 to 2: 1 (number of vinyl groups : number of thiol groups), such as a ratio of from 1 : 10 to 1.5: 1 (number of vinyl groups : number of thiol groups).

[0058] A number of possible non-reactive diluents may be used, provided that the diluent does not substantially react with the polyvinyl silicone or the polymercapto silicone and also has a boiling point in a range of about 80 °C to about 250 °C. In particular embodiments, the non- reactive diluent has a boiling point in a range of about 100 °C to about 250 °C. In some embodiments, the non-reactive diluent has a boiling point of less than about 160 °C, less than about 200 °C, or less than about 240 °C. Unless otherwise indicated, all boiling points referenced herein are at standard atmospheric pressure (1 atm).

[0059] Non-reactive diluents useful in the present invention are, in general, organic liquids that can be polar or nonpolar, and protic or aprotic. In particular embodiments, the non-reactive diluent comprises an alkane (e.g., a C7-C15 alkane) and / or a volatile silicone diluent, and / or an acetate (e.g., a C3-C9 acetate).

[0060] The non-reactive diluents are preferably non-flammable, non-hygroscopic, low odor, and low viscosity. In some embodiments, the non-reactive diluent has an autoignition temperature greater than about 300 °C, greater than about 400 °C, or greater than about 600 °C (i.e., as measured in accordance with the procedure described in ASTM E659). In some embodiments, the non-reactive diluent has a flash point of greater than about 50 °C, greater than about 80 °C, greater than about 100 °C, or greater than about 140 °C as measured by the Pensky-Martens closed cup method (e.g., ASTM D93, EN ISO 2719, or IP 34).

[0061] In some embodiments, the non-reactive diluent is present in a resin composition of the invention in an amount of from about 5 percent by weight to about 50 percent by weight, including in an amount of about 5 percent by weight to about 20 percent by weight. In some embodiments, the non-reactive diluent is included in the resin composition in an amount of from about 1 or 5 percent by weight to about 10, about 15 or about 20 percent by weight.

[0062] In some embodiments, Resin Composition 1 may further include a divinyl linear silicone having a molecular weight (Mn) in a range of 0.5 kDa to 10 kDa as a chain extender. In some embodiments, such a chain extender may have a molecular weight (Mn) in a range of 1 kDa to 2 kDa.

[0063] In some embodiments, Resin Composition 1 includes: a polyvinyl silicone at a concentration in a range of about 25 weight percent to about 99 weight percent, (e.g., in a range of about 50 weight percent to about 90 weight percent); a polymercapto silicone at a concentration in a range of about 0.5 weight percent to about 20 weight percent, (e.g., in a range of about 2 weight percent to about 15 weight percent); a non-reactive diluent present at a concentration in a range of about 5 weight percent to about 50 weight percent (e.g., in a range of about 5 weight percent to about 20 weight percent); and a filler (as described herein) present at a concentration in a range of about 2 weight percent to about 50 weight percent (e.g., in a range of about 5 weight percent to about 30 weight percent).

[0064] In some embodiments, Resin Composition 1 has a viscosity in a range of 500 centipoise (cP) to 100,000 cP at 40 °C when measured in accordance with the procedure outlined in Example 1. In some embodiments, Resin Composition 1 has a viscosity of not more than about 3500 cP, not more than about 3000 cP, or not more than about 2500 cP at 40 °C, when measured in accordance with the procedure outlined in Example 1.

[0065] Additional optional components may be added to Resin Composition 1, as discussed in further detail below.

[0066] Resin Composition 2: Resin Compositions Including Vinyl Siloxane Crosslinkers

[0067] Conventional silicone thiol-ene crosslinked resins typically include a divinyl silicone as the main elastic component and a polymercapto silicone as the cross-linker. Resin 2 Compositions of the invention, however, include a dimercapto silicone as the main elastic component and a polyvinyl silicone (including three or more vinyl groups, or more than two vinyl groups on average) as the cross-linking agent. Such resin compositions may have certain advantages over conventional resins. For example, polythiol polydimethylsiloxane (PDMS) crosslinkers (and other polymercapto silicones) may not be fully soluble in unfunctionalized PDMS or divinyl PDMS (or other polyvinyl silicones) and this may lead to rheological issues that limit use of such conventional silicone-based thiol-ene resins - particularly those including a significant amount of filler - with certain additive manufacturing processes. However, endcapped dimercapto silicones are typically miscible in PDMS and vinyl PDMS (and the like) and so such rheological problems may be reduced or eliminated. In addition, in Resin Composition 2, as the multi-functional vinyl species act as the cross-linker, a molar excess of this component is typically used rather than an excess of a thiol-terminated compound. In some embodiments, Resin Composition 2 has an excess of free vinyl groups relative to free thiol groups. Therefore, odors from free thiols in these resin compositions may be reduced or eliminated.

[0068] In some embodiments, for Resin Composition 2, the polymercapto silicone and the polyvinyl silicone are included in the resin compositions in a thiol to vinyl ratio of from 1 :50 to 2: 1 (number of thiol groups : number of vinyl groups), such as a ratio of from 1 : 10 to 1 : 1 (number of thiol groups : number of vinyl groups).

[0069] Accordingly, in some embodiments, in Resin Composition 2, the silicone portion of a polymercapto silicone is a linear polydimethylsiloxane (PDMS). In some embodiments, the polymercapto silicone is a dimercapto silicone. In some embodiments, the polymercapto silicone is an end-capped dimercapto PDMS (a PDMS linear chain with a thiol group at each terminus, such as Gelest DMS-SM21, Gelest, Inc.).

[0070] The molecular weight of the polymercapto silicone may vary. However, in some embodiments, the polymercapto silicone has a molecular weight (Mn) in a range of 5 kDa to 300 kDa (e.g., 30 kDa to 100 kDa). In some embodiments, the polymercapto silicone is a prepolymer in a range of 30 kDa to 300 kDa and provides the primary elastic portion of the resulting cross-linked silicone polymer formed by the additive manufacturing process.

[0071] In some embodiments, the polymercapto silicone is present in Resin Composition 2 at a concentration in a range of about 25 weight percent to about 99 weight percent (e.g., at about 50 wt %, about 60 wt %, about 70 wt %, about 80 wt%, about 90 wt %, about 99 wt%, and any range defined between any two of the foregoing values).

[0072] In some embodiments, in Resin Composition 2, the polyvinyl silicone includes at least three vinyl groups (and / or on average more than two vinyl groups). In some embodiments, at least three of the vinyl groups in the polyvinyl silicone are present on a terminal portion of the siloxane chain. For example, in some embodiments, the polyvinyl silicone is a branched silicone that includes a vinyl group at the end of each siloxane chain. In some embodiments, the polyvinyl silicone has a molecular weight (Mn) in a range of about 500 Da to about 10 kDa (e.g., 2 kDa to 5 kDa). Thus, the polyvinyl silicone monomer and / or prepolymer acts primarily as a crosslinker in the resulting silicone polymer thus formed. In some embodiments, the polyvinyl silicone is a vinyl siloxane Q-resin (a branched siloxane core functionalized with many vinyl groups, such as Siltech Silmer VQ20, Siltech Corporation)

[0073] In some embodiments, the polyvinyl silicone is present in Resin Composition 2 at a concentration in a range of about 0.5 weight percent to about 20 weight percent (e.g. at about 0.5 wt%, about 1 wt%, about 2 wt%, about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, about 10 wt%, about 11 wt%, about 12 wt%, about 13 wt%, about 14 wt%, about 15 wt%, and any range defined between any two of the foregoing values).

[0074] In some embodiments, Resin Composition 2 may further include a divinyl linear silicone having a molecular weight (Mn) in a range of 0.5 kDa to 10 kDa as a chain extender. In some embodiments, such a chain extender may have a molecular weight (Mn) in a range of 1 kDa to 2 kDa (such as Siltech Silmer VIN 200, Siltech Corporation).

[0075] In some embodiments, Resin Composition 2 includes:

[0076] (i) about 0.5% by weight to about 10% or about 20% by weight of a polyvinyl silicone monomer and / or prepolymer at least three vinyl groups, or an average number of vinyl groups greater than 2;

[0077] (ii) a polymerapto silicone monomer and / or prepolymer (e.g., a thiol endcapped linear silicone);

[0078] (iii) a photoinitiator; and

[0079] (iv) optionally, a filler (e.g., at about 5% by weight to about 30 % by weight), as described below.

[0080] In some embodiments, Resin Composition 2 has a viscosity in a range of 100 centipoise (cP) to 50,000 cP at 40 °C when measured in accordance with the procedure outlined in Example 1.

[0081] Additional optional components may be added to resin compositions including non- reactive diluent(s). Further, a non-reactive diluent having a boiling point of from about 80 or 100 °C to about 160, 200, 240 or 250 °C, as described with respect to Resin Composition 1, may also optionally be included.

[0082] Optional Resin Components

[0083] In some embodiments, Resin Composition 1 and / or Resin Composition 2 may include other optional components. For example, in some embodiments of the invention, a resin composition includes at least one additional component, including but not limited to, a UV absorber (e.g., a pigment and / or dye), an antioxidant, a plasticizer, a filler, a radical inhibitor, and a thermal inhibitor.

[0084] In some embodiments, resin compositions include a non-reactive pigment or dye that absorbs light, particularly UV light. Suitable examples of such light absorbers include, but are not limited to: (i) titanium dioxide (e.g., included in an amount of from 0.05 or 0.1 to 1 or 5 percent by weight), (ii) carbon black (e.g., included in an amount of from 0.05 or 0.1 to 1 or 5 percent by weight), and / or (iii) an organic ultraviolet light absorber such as a hydroxybenzophenone, hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone, hydroxyphenyltriazine, and / or benzotriazole ultraviolet light absorber (e.g., Mayzo BLS® 1326) (e.g., included in an amount of 0.001 or 0.005 to 1, 2 or 4 percent by weight). Examples of suitable organic ultraviolet light absorbers include, but are not limited to, those described in U.S. Pat. Nos. 3,213,058, 6,916,867, 7,157,586, and 7,695,643, the disclosures of which are incorporated herein by reference.

[0085] In some embodiments, the resin compositions include an antioxidant. A number of possible antioxidants may be used. Examples of antioxidants include, but are not limited to, phenols, hindered phenols, phosphites, thiosynergists, and combinations thereof (available, for example, from Mayzo, Suwanee, Ga.).

[0086] In some embodiments, the resin compositions include a plasticizer. A number of possible plasticizers may be used. Examples of plasticizers include, but are not limited to, nonvolatile silicone fluids.

[0087] In some embodiments, the resin compositions may include a filler. A number of possible fillers may be used, including tougheners and / or core-shell rubbers. Any suitable filler may be used in connection with the present invention, depending on the properties desired in the part or object to be made. Thus, fillers may be solid or liquid, organic or inorganic, and may include reactive and non-reactive rubbers: siloxanes, acrylonitrile-butadiene rubbers; reactive and non-reactive thermoplastics (including but not limited to: poly(ether imides), maleimide-styrene terpolymers, polyarylates, polysulfones and polyethersulfones, etc.), inorganic fillers such as silicates (such as talc, clays, silica, mica), glass, carbon nanotubes, graphene, cellulose nanocrystals, etc., including combinations of two or more of the foregoing. Suitable fillers include tougheners, such as core-shell rubbers, as discussed below. In some embodiments, the filler is a hydrophobic or hydrophilic fumed or precipitated silica, titanium dioxide, or carbon black, and may be present in the composition at a concentration of about 5 wt% to about 30 wt% (e.g., about 10 wt% to about 20 wt %). One or more polymeric and / or inorganic tougheners can be used as a filler in the present invention. The toughener may be uniformly distributed in the form of particles in the cured product. The particles could be less than 5 microns (pm) in diameter. Such tougheners include, but are not limited to, those formed from elastomers, branched polymers, hyperbranched polymers, dendrimers, rubbery polymers, rubbery copolymers, block copolymers, core-shell particles, oxides or inorganic materials such as clay, polyhedral oligomeric silsesquioxanes (POSS), carbonaceous materials (e.g., carbon black, carbon nanotubes, carbon nanofibers, fullerenes), ceramics and silicon carbides, with or without surface modification or functionalization.

[0088] Core-shell rubbers are particulate materials (particles) having a rubbery core. Such materials are known and described in, for example, US Patent Application Publication No. 2015 / 0184039, as well as US Patent Application Publication No. 2015 / 0240113, and U.S. Pat. Nos. 6,861,475, 7,625,977, 7,642,316, 8,088,245, and elsewhere. In some embodiments, the core-shell rubber particles are nanoparticles (i.e., having an average particle size of less than 1000 nanometers (nm)). Generally, the average particle size of the core-shell rubber nanoparticles is less than 500 nm, e.g., less than 300 nm, less than 200 nm, less than 100 nm, or even less than 50 nm. Typically, such particles are spherical, so the particle size is the diameter; however, if the particles are not spherical, the particle size is defined as the longest dimension of the particle. Suitable core-shell rubbers include, but are not limited to, those sold by Kaneka Corporation under the designation Kaneka Kane Ace, including the Kaneka Kane Ace 15 and 120 series of products, including Kaneka Kane Ace MX 120, Kaneka Kane Ace MX 153, Kaneka Kane Ace MX 154, Kaneka Kane Ace MX 156, Kaneka Kane Ace MX 170, Kaneka Kane Ace MX 257, and Kaneka Kane Ace MX 120 core-shell rubber dispersions, and mixtures thereof.

[0089] The resin composition may include other solid particles suspended or dispersed therein. The particles can be metallic, organic / polymeric, inorganic, or composites or mixtures thereof. The particles can be nonconductive, semi -conductive, or conductive (including metallic and non-metallic or polymer conductors); and the particles can be magnetic, ferromagnetic, paramagnetic, or nonmagnetic. The particles can be of any suitable shape, including spherical, elliptical, cylindrical, etc. The particles can be of any suitable size (for example, ranging from 1 nm to 20 pm average diameter). The particles can comprise an active agent or detectable compound as described below, though these may also be provided dissolved or solubilized in the liquid resin as also discussed below. For example, magnetic or paramagnetic particles or nanoparticles can be employed. Although in some embodiments, no odor scavenger is present in the resin composition, in some embodiments, an odor scavenger is present. In some embodiments, the odor scavenger includes at least one, or in some embodiments two or all three of, a constituent from the following three categories:

[0090] (a) Odor Absorbents / Adsorbents: The odor absorbents / adsorbents include, but not limited to, carbon black, zeolite, a- / p- / y-cyclodextrin, chitosan, etc.

[0091] (b) Blocked Isocyanate Odor Scavanger: The blocked or reactive blocked isocyanate (e.g., prepolymer) odor scavengers may include a polyisocyanate oligomer produced by the reaction of at least one diisocyanate, e.g., a diisocyanate such as hexamethylene diisocyanate (HDI), bis-(4-isocyanatocyclohexyl)methane (HMDI), isophorone diisocyanate (IPDI), etc., a triisocyanate, etc., with at least one polyol, e.g., a polyether or polyester or polybutadiene or polysiloxane diol. In some embodiments, the blocked prepolymer is blocked by reaction of a polyisocyanate with a blocking agent including, but not limited to, diethyl malonate (DEM), 3,5-dimethylpyrazole (DMP), methylethylketoxime (MEKO), caprolactam, etc. In some embodiments, the reactive blocked prepolymer is blocked by reaction of a polyisocyanate with an amine (meth)acrylate monomer blocking agent (e.g., tertiary -butylaminoethyl methacrylate (TBAEMA), tertiary pentylaminoethyl methacrylate (TPAEMA), tertiary hexylaminoethyl methacrylate (THAEMA), tertiary-butylaminopropyl methacrylate (TBAPMA), acrylate analogs thereof, and mixtures thereof.

[0092] (c) Multi-functional Epoxy Odor Scavenger: In some embodiments, the multifunctional epoxy odor scavengers include, but are not limited to, bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE), mono-phenyl functional tris(epoxy terminated polydimethylsiloxane), epoxypropoxypropyl terminated polydimethylsiloxane, glycidyl epoxy functionalized POSS cage mixture, ERISYS® GE Series glycidyl ether monomers and modifiers, etc. Catalysts may be used along with the epoxy odor scavengers to improve reaction rate and conversion of epoxy -thiol cure. Amines and imidazoles are common catalysts for accelerating co-reactive epoxy cure. Examples of these catalysts include, but are not limited to, triethanolamine (TEA), benzyldimethylamine (BDMA), 1 -methylimidazole, (dimethylaminomethyl)phenol, 2,4,6-Tris(dimethylaminomethyl)phenol, vinylphoshonic acid, and an encapsulated imidazole (Technicure® LC-80). Some epoxy curing agents are selfaccelerating and can act as a catalyst for epoxy -thiol cure. Examples of these catalysts include, but are not limited to, dicyandiamide (DICY) and N,N-dimethyl phenyl urea (Technicure® PDU-250). Co-reactive epoxy curing can also be accelerated by Bronsted acid or Lewis acid (see WO1994004582 Al). Examples of these catalysts include, but are not limited to, vinylphosphonic acid, sulfonic acids, and zinc chloride. The catalysts may be included in the polymerizable liquid in any suitable amount, typically from 0.1 or 0.5 percent by weight, up to about 10 or 15 percent by weight, or more.

[0093] Resin compositions of the invention may optionally have other ingredients solubilized therein, including active compounds or pharmaceutical compounds, detectable compounds (e.g., fluorescent, phosphorescent, radioactive), again depending upon the particular purpose of the product being fabricated. Examples of such additional ingredients include, but are not limited to, proteins, peptides, nucleic acids (DNA, RNA) such as siRNA, sugars, small organic compounds (drugs and drug-like compounds), etc., including combinations thereof.

[0094] Additive Manufacturing

[0095] Also provided according to embodiments of the invention are methods of making a three-dimensional object using a resin composition of the invention. Such three-dimensional objects may be made by additive manufacturing processes that include the steps of: (a) providing a digital model of the object (for example, a lattice or object including the lattice); and then (b) producing that object from the digital model by an additive manufacturing process.

[0096] Numerous additive manufacturing processes are known. Suitable techniques include, but are not limited to, techniques such as selective laser sintering (SLS), fused deposition modeling (FDM), stereolithography (SLA), material jetting including three-dimensional printing (3 DP) and multij et modeling (MJM)(including Multi -Jet Fusion such as available from Hewlett Packard), and others. See, e.g., H. Bikas et al., Additive manufacturing methods and modelling approaches: a critical review, Int. J. Adv. Manuf. Technol. 83, 389-405 (2016).

[0097] Stereolithography, including bottom-up and top-down techniques, are known and described in, for example, U.S. Pat. No. 5,236,637 to Hull, U.S. Pat. Nos. 5,391,072 and 5,529,473 to Lawton, U.S. Pat. No. 7,438,846 to John, U.S. Pat. No. 7,892,474 to Shkolnik, U.S. Pat. No. 8,110,135 to El-Siblani, U.S. Patent Application Publication No. 2013 / 0292862 to Joyce, and US Patent Application Publication No. 2013 / 0295212 to Chen et al.

[0098] In some embodiments, the object is formed by continuous liquid interface production (CLIP). CLIP is known and described in, for example, PCT Application Nos. PCT / US2014 / 015486 (U.S. Pat. No. 9,211,678); PCT / US2014 / 015506 (U.S. Pat. No. 9,205,601), PCT / US2014 / 015497 (U.S. Pat. No. 9,216,546), and in J. Tumbleston, D. Shirvanyants, N. Ermoshkin et al., Continuous liquid interface production of 3D Objects, Science 347, 1349-1352 (2015). See also R. Janusziewcz et al., Layerless fabrication with continuous liquid interface production, Proc. Natl. Acad. Sci. USA 113, 11703-11708 (2016). In some embodiments, CLIP employs features of a bottom-up three-dimensional fabrication as described above, but the irradiating and / or the advancing steps are carried out while also concurrently maintaining a stable or persistent liquid interface between the growing object and the build surface or window, such as by: (i) continuously maintaining a dead zone of polymerizable liquid (resin composition) in contact with the build surface, and (ii) continuously maintaining a gradient of polymerization zone (such as an active surface) between the dead zone and the solid polymer and in contact with each thereof, the gradient of polymerization zone comprising the polymerizable liquid in partially-cured form. In some embodiments of CLIP, the optically transparent member comprises a semipermeable member (e.g., a fluoropolymer), and the continuously maintaining a dead zone is carried out by feeding an inhibitor of polymerization through the optically transparent member, thereby creating a gradient of inhibitor in the dead zone and optionally in at least a portion of the gradient of polymerization zone. Other approaches for carrying out CLIP that can be used in the present invention and obviate the need for a semipermeable “window” or window structure include utilizing a liquid interface comprising an immiscible liquid (see L. Robeson et al., WO 2015 / 164234), generating oxygen as an inhibitor by electrolysis (see I. Craven et al., WO 2016 / 133759), and incorporating magnetically positionable particles to which the photoactivator is coupled into the polymerizable liquid (see J. Rolland, WO 2016 / 145182).

[0099] Other examples of methods and apparatus for carrying out particular embodiments of CLIP include, but are not limited to: Batchelder et al., Continuous liquid interface production system with viscosity pump, US Patent Application Pub. No. US 2017 / 0129169; Sun and Lichkus, Three-dimensional fabricating system for rapidly producing objects, US Patent Application Pub. No. US 2016 / 0288376; Willis et al., 3d print adhesion reduction during cure process, US Patent Application Pub. No. US 2015 / 0360419; Lin et al., Intelligent 3d printing through optimization of 3d print parameters, US Patent Application Pub. No. US 2015 / 0331402; and D. Castanon, Stereolithography System, US Patent Application Pub. No. US 2017 / 0129167.

[0100] In some embodiments, the three-dimensional object is formed using a method or apparatus / system schematically illustrated in FIG. 1. Such a system includes a user interface 3 for inputting instructions (such as selection of an object to be produced, and selection of features to be added to the object), a controller 4, and an additive manufacturing apparatus 5 such as described above. An optional washer (not shown) can be included in the system if desired, or a separate washer can be utilized. Similarly, a heater or oven (not shown) can be included in the system, although a separately operated oven can also be utilized. Connections between components of the system can be by any suitable configuration, including wired and / or wireless connections. The components may also communicate over one or more networks, including any conventional, public and / or private, real and / or virtual, wired and / or wireless network.

[0101] Controller 4 may be of any suitable type, such as a general -purpose computer. Typically, the controller 4 will include at least one processor 4a, a volatile (or “working”) memory 4b, such as random-access memory, and at least one non-volatile or persistent memory 4c, such as a hard drive or a flash drive. The controller 4 may use hardware, software implemented with hardware, firmware, tangible computer-readable storage media having instructions stored thereon, and / or a combination thereof, and may be implemented in one or more computer systems or other processing systems. The controller 4 may also utilize a virtual instance of a computer. As such, the devices and methods described herein may be embodied in any combination of hardware and software that may all generally be referred to herein as a “circuit,” “module,” “component,” and / or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable media having computer readable program code embodied thereon.

[0102] Any combination of one or more computer readable media may be utilized. The computer readable media may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non- exhaustive list) of the computer readable storage medium would include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an appropriate optical fiber with a repeater, a portable compact disc read-only memory (CD- ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0103] A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, radio frequency (RF), etc., or any suitable combination of the foregoing.

[0104] The at least one processor 4a of the controller 4 may be configured to execute computer program code for carrying out operations for aspects of the present invention, which computer program code may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, or the like, conventional procedural programming languages, such as the “C” programming language, Visual Basic, Fortran 2003, COBOL 2002, PHP, ABAP, dynamic programming languages such as Python, PERL, Ruby, and Groovy, or other programming languages.

[0105] The at least one processor 4a may be, or may include, one or more programmable general purpose or special-purpose microprocessors, digital signal processors (DSPs), programmable controllers, application specific integrated circuits (ASICs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), trusted platform modules (TPMs), or a combination of such or similar devices, which may be collocated or distributed across one or more data networks.

[0106] Connections between internal components of the controller 4 are shown only in part and connections between internal components of the controller 4 and external components are not shown for clarity, but are provided by additional components known in the art, such as busses, input / output boards, communication adapters, network adapters, etc. The connections between the internal components of the controller 4, therefore, may include, for example, a system bus, a Peripheral Component Interconnect (PCI) bus or PCI-Express bus, a HyperTransport or industry standard architecture (ISA) bus, a small computer system interface (SCSI) bus, a universal serial bus (USB), IIC (I2C) bus, an Advanced Technology Attachment (ATA) bus, a Serial ATA (SATA) bus, and / or an Institute of Electrical and Electronics Engineers (IEEE) standard 1394 bus, also called “Firewire.”

[0107] The user interface 3 may be of any suitable type. The user interface 3 may include a display and / or one or more user input devices. The display may be accessible to the at least one processor 4a via the connections between the system components. The display may provide graphical user interfaces for receiving input, displaying intermediate operation / data, and / or exporting output of the methods described herein. The display may include, but is not limited to, a monitor, a touch screen device, etc., including combinations thereof. The input device may include, but is not limited to, a mouse, keyboard, camera, etc., including combinations thereof. The input device may be accessible to the at least one processor 4a via the connections between the system components. The user interface 3 may interface with and / or be operated by computer readable software code instructions resident in the volatile memory 4b that are executed by the processor 4a.

[0108] In some embodiments, resin compositions of the invention (e.g., Resin Composition 1 and Resin Composition 2) are “single cure” resins, meaning that the polymerizable components are solidified by UV light during the additive manufacturing process. In some embodiments, however, there may be residual non-reactive diluent present in the three-dimensional objects formed by the additive manufacturing process. To remove this non-reactive diluent, after an optional cleaning step, the object may be heated. In some embodiments, the three-dimensional object is heated to a temperature in a range of about 70 °C to about 200 °C to volatilize and remove (e.g., partially, substantially, or completely remove) any non-reactive diluent. While the non-reactive diluent is typically removed during such a baking step, in some embodiments, the non-reactive diluent may be removed using a solvent exchange whereby the object is washed in a more volatile solvent first, thereby removing some, most, or all of the non-reactive diluent and replacing it with the more volatile solvent. Then, the more volatile solvent may be removed during the heating process.

[0109] In some embodiments, methods may include the additive manufacturing, and any or all of: cleaning (washing / spinning / vapor-spinning / wiping), post-UV cure (LED, broad spectrum lamp, heated / un-heated), and bake (including in a uncontrolled or controlled environment such as inert, air, humid, and the like).

[0110] In some embodiments, the three-dimensional objects are heated in an inert atmosphere, defined herein as an atmosphere containing less oxygen than air or being substantially devoid of oxygen. Inert atmosphere ovens in which the oven chamber is purged with an inert gas such as nitrogen or argon are known and available from Gruenberg / Thermal Products Solutions, 2821 Old Route 15, New Columbia, Pa. 17856 USA; Despatch Thermal Processing Technology, 8860 207thStreet, Minneapolis, Minn. 55044 USA, and others.

[0111] In some embodiments, before, after, or concurrently with said heating step, volatilized diluent may be condensed out of the atmosphere (e.g., an inert atmosphere) in an amount sufficient to reduce the duration of the heating step. Any suitable condenser structure can be employed, such as a chilling coil in the oven chamber itself (with a liquid collector such as a drip pan or funnel with drain operatively associated with the condenser); an assembly for removing a side-stream of gas from the oven chamber, condensing out volatilized solvent, and returning the side-stream to the oven chamber; etc. Numerous such condensation systems are known (see, for example, U.S. Pat. No. 5,220,796) and are available from oven manufacturers such as those noted above.

[0112] In some embodiments of the invention, evaporation of the non-reactive diluent will lead to volumetric shrinkage in the final object. As such, in some embodiments, methods include the steps of: (a) providing a digital model of the 3D object (e.g., lattice or object including the lattice); (b) applying an isotropic volumetric scale factor to said 3D object sufficient to offset volumetric shrinkage due to solvent removal to produce a modified digital model; and (b) producing that object from the modified digital model by an additive manufacturing process.

[0113] Three-Dimensional Products

[0114] In some embodiments, three-dimensional products produced by the methods and resin compositions described herein may include one or more repeating structural elements, including, for example, structures that are (or substantially correspond to) enclosed cavities, partially-enclosed cavities, repeating unit cells or networks of unit cells, foam cell, Kelvin foam cell or other open-cell or closed-cell foam structures, crisscross structures, overhang structures, cantilevers, microneedles, fibers, paddles, protrusions, pins, dimples, rings, tunnels, tubes, shells, panels, beams (including I-beams, U-beams, W-beams and cylindrical beams), struts, ties, channels (whether open, closed or partially enclosed), waveguides, triangular structures, tetrahedron or other pyramid shape, cube, octahedron, octagon prism, icosidodecahedron, rhombic triacontahedron or other polyhedral shapes or modules (including Kelvin minimal surface tetrakaidecahedra, prisms or other polyhedral shapes), pentagon, hexagonal, octagon and other polygon structures or prisms, polygon mesh or other three-dimensional structure. In some embodiments, the object may include combinations of any of these structures or interconnected networks of these structures. In an example embodiment, all or a portion of the structure of the 3D formed object may correspond (or substantially correspond) to one or more Bravais lattice or unit cell structures, including cubic (including simple, body-centered or facecentered), tetragonal (including simple or body-centered), monoclinic (including simple or end-centered), orthorhombic (including simple, body-centered, face-centered or end-centered), rhombohedral, hexagonal and triclinic structures. In some embodiments, the object may include shapes or surfaces that correspond (or substantially correspond) to a catenoid, helicoid, gyroid or lidinoid, other triply periodic minimal surface (TPMS), or other geometry from the associate family (or Bonnet family) or Schwarz P (“Primitive”) or Schwarz D (“Diamond”), Schwarz H (“Hexagonal”) or Schwarz CLP (“Crossed layers of parallels”) surfaces, argyle or diamond patterns, lattice or other pattern or structure.

[0115] In some embodiments, three-dimensional products produced by the methods herein may include an array of interconnected lattice unit cells (e.g., an open cell lattice), on one or more portions thereof (e.g., a surface portion). In some embodiments, the product may include a triply periodic unit (i.e., a unit that repeats in three dimensions), such as a triply periodic surface or triply periodic minimal surface. See, e.g., U.S. Pat. No. 9,440,216 to Ryan, and U.S. Pat. No. 7,718,109 to Robb et al.

[0116] The present invention is explained in greater detail in the following non-limiting examples.

[0117] EXAMPLES

[0118] Definitions

[0119] EHDA - 2-ethylhexyl-4-dimethylaminobenzoate CAS NO. 21245-02-3

[0120] ITX - isopropyl-9H-thioxanthen-9-one, mixture of 2- and 4-isomers CAS NO. 75081-21-9 MeHQ - 4-m ethoxyphenol CAS NO. 150-76-5

[0121] DragonSkin 30 Part A - vinyl-containing, silica-filled platinum addition cure silicone compound (Part A only) used for special effects and mold-making applications

[0122] Part Bl - linear poly (dimethyl- mercaptopropylmethyl-siloxane) random co-polymer, 5 mol% mercaptopropylmethyl siloxane

[0123] Part B2 - linear poly (dimethyl- mercaptopropylmethyl-siloxane) random co-polymer, 14.2 mol% mercaptopropylmethyl siloxane

[0124] Viscosity Measurement Methods

[0125] The viscosity of the resin formulations as described herein are measured at 40 °C using a Brookfield viscometer (Model DVI) equipped with an SC4-31 spindle. The bubble-free sample (9.0 g) was poured into the sample chamber and the temperature was equilibrated for 15 minutes. After equilibration, the RPM of the spindle was adjusted to target a torque of approximately 50% (RPM of roughly 3.0-1.5 depending on the sample viscosity), wherein the viscosity is measured.

[0126] Example 1

[0127] Referring to the formulations referenced below, the appropriate amounts of Part A, Part B, and solvent (if necessary) were weighed out and placed into a closed container. The container was mixed via high-shear rotary mixer. Afterwards, the mixture was placed in a cassette with heating capabilities and printed on a Carbon M2 series printer (Carbon, Inc., Redwood City, California, USA). After printing, parts were spun on a platform spinner, wiped, and placed in a 405 nm PCU LED chamber under an inert atmosphere for 10 minutes. If the formulation contained solvent, the parts were then baked for 3 hours at 120 °C.

[0128] DS30 ITX / EHDA / MeHQ (Part A)

[0129] Formulation A and Formulation B

[0130] Formulation C Formulation D

[0131] Formulation F

[0132] Formulation G

[0133] FIG. 2 is a plot of the stress-strain curves for each of the Formulations A - G and shows their comparative properties.

[0134] Comparing Formulation A to Formulation B demonstrates that the baking process has no / minimal effect on mechanical properties in the solvent-free system.

[0135] Comparing Formulations A and B to Formulations C, D, and F (or E to G) demonstrates that the presence of solvent, even after removing it from the system during bake, causes a softer polymer network structure as the network forms a looser / less ideal network when cured with solvent present.

[0136] Comparing Formulation D to Formulation F demonstrates that more solvent has more of a softening effect. Comparing Formulation C to Formulation D demonstrates that the weight fraction (and therefore approximately volume fraction) is the main cause of network softening, and the solvent identity has little effect on the final network properties.

[0137] Comparing Formulation E to Formulation A and Formulation G to Formulation F demonstrates that different cross-linker structure results in different mechanical properties (in this case, Part B2 is stiffer than Part Bl, both with and without solvent).

[0138] Example 2

[0139] The following two compositions were prepared:

[0140] Formulation H: Resin composition 2 example (vinyl cross-linked)

[0141] Formulation I: Resin composition 2 comparative example (thiol cross-linked)

[0142] Both Formulation H and Formulation I have similar cross-link density and chain extension, but Formulation H uses a mercapto Q-resin as a cross-linker and Formulation I uses a vinyl Q-resin as a cross-linker. The VinykThiol excess in Formulation H is similar to the ThikVinyl excess in Formulation I. Formulation H results in an optically clear liquid formulation whereas Formulation I forms an opaque multi-phase liquid-liquid emulsion of higher viscosity. Therefore, the formulation according to the invention provides improved physical (solubility) properties relative to a conventional (comparative) formulation.

[0143] The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents included therein.

Claims

We claim:

1. An additive manufacturing resin composition, comprising:(i) a polyvinyl silicone monomer and / or prepolymer (e.g., a divinyl silicone prepolymer having a molecular weight (Mn) in a range of 5 kDa to 300 kDa);(ii) a polymercapto silicone monomer and / or prepolymer (e.g., a polymercapto silicone prepolymer having a molecular weight (Mn) in a range of 500 Da to 10 kDa);(iii) a photoinitiator; and(iv) a non-reactive diluent, wherein the non-reactive diluent has a boiling point of from about 80 °C to about 250 °C.

2. The resin composition of claim 1, wherein the non-reactive diluent has a boiling point of from about 100 °C to about 250 °C.

3. The resin composition of claim 1 or claim 2, wherein the resin composition has a viscosity in a range of about 500 centipoise (cP) to about 100,000 cP.

4. The resin composition of any one of claims 1-3, wherein the non-reactive diluent is present in an amount of from about 5 percent by weight to about 50 percent by weight (e.g., about 5 percent by weight to about 20 percent by weight).

5. The resin composition of any one of claims 1-4, wherein the non -reactive diluent comprises an alkane (e.g., a C7-C15 alkane) and / or a volatile silicone diluent.

6. The resin composition of any one of claims 1-4, wherein the non-reactive diluent comprises an acetate (e.g., a C3-C9 acetate).

7. The resin composition of any one of claims 1-6, wherein the resin composition further comprises at least one additional component selected from the group consisting of a radical inhibitor; a UV absorber (e.g., a pigment and / or dye); an antioxidant; a plasticizer; a filler; and a thermal inhibitor.

8. The resin composition of claim 7, whereinthe polyvinyl silicone monomer and / or prepolymer is present at a concentration in a range of about 25 weight percent to about 99 weight percent (e.g., about 50 weight percent to about 90 weight percent); the polymercapto silicone monomer and / or prepolymer is present at a concentration in a range of 0.5 weight percent to 20 weight percent (e.g., about 2 weight percent to about 15 weight percent); the non-reactive diluent is present at a concentration in a range of about 5 weight percent to about 50 weight percent (e.g., about 5 weight percent to about 20 weight percent); and the filler is present at a concentration in a range of about 2 weight percent to 50 weight percent (e.g., about 5 weight percent to about 30 weight percent).

9. A method of making a three-dimensional (3D) object from a light polymerizable resin (e.g., via bottom-up stereolithography), comprising the steps of:(a) providing the additive manufacturing resin composition of any one of claims 1-8;(b) producing the 3D object from the resin composition by reacting the polyvinyl silicone monomers and / or prepolymers and the polymercapto silicone monomers and / or prepolymers;(c) optionally cleaning the 3D object; and then(d) heating the 3D object (e.g., at a temperature in a range of about 70°C to about 200°C) to volatilize and remove (e.g., partially, substantially, or completely remove) the non- reactive diluent.

10. The method of claim 9, wherein producing step (b) comprises providing a digital model of the 3D object; applying an iso-tropic volumetric scale factor to the 3D object sufficient to offset volumetric shrinkage due to solvent removal to produce a modified digital model; and then producing the 3D object using the modified digital model.

11. The method of claim 9 or 10, wherein the heating step is carried out with the 3D object in an inert atmosphere.

12. The method of any one of claims 9-11, further comprising: concurrently with the heating step, condensing volatilized non-reactive diluent in an amount sufficient to reduce the duration of the heating step.

13. An additive manufacturing resin composition, comprising:(i) about 0.5% by weight to about 10% or about 20% by weight of a polyvinyl silicone monomer and / or prepolymer (e.g., a polyvinyl silicone monomer and / or prepolymer having three or more vinyl groups per molecule, or on average more than 2 vinyl groups per molecule), optionally wherein the polyvinyl silicone monomer and / or prepolymer has a molecular weight (Mn) in a range of about 500 g / mol to about 10,000 g / mol;(ii) a polymercapto silicone monomer and / or prepolymer (e.g., a dimercapto silicone monomer and / or prepolymer having terminal thiol functional groups), optionally wherein the polymercapto silicone monomer and / or prepolymer has a molecular weight (Mn) in a range of about 5000 g / mol to about 300,000 g / mol;(iii) a photoinitiator;(iv) optionally, a filler; and(v) optionally, a non-reactive diluent, wherein the non-reactive diluent has a boiling point of from about 80 °C to about 250 °C.

14. The resin composition of claim 13, wherein the polymercapto silicone monomer and / or prepolymer is present at a concentration in a range of about 25 weight percent to about 99 weight percent (e.g., in a range of about 50 weight percent to about 90 weight percent).

15. The resin composition of claim 13 or claim 14, wherein the resin composition further comprises at least one additional component selected from the group consisting of an antioxidant, a plasticizer, a radical inhibitor, a UV absorber (e.g., a pigment and / or dye), a filler, and a thermal inhibitor.

16. The resin composition of claim 15, wherein the polyvinyl silicone monomer and / or prepolymer is present at a concentration in a range of about 0.5 weight percent to about 20 weight percent (e.g., in a range of about 2 weight percent to about 15 weight percent); the polymercapto silicone monomer and / or prepolymer is present at a concentration in a range of about 25 weight percent to about 99 weight percent (e.g., in a range of about 50 weight percent to about 90 weight percent); and the filler is present at a concentration in a range of about 2 weight percent to about 50 weight percent (e.g., in a range of about 5 weight percent to about 30 weight percent).

17. A method of making a three-dimensional (3D) object from a light polymerizable resin (e.g., via bottom-up stereolithography), comprising the steps of:(a) providing the additive manufacturing resin composition of any one of claims 13-16;(b) producing the 3D object from the resin composition by reacting the polyvinyl silicone monomers and / or prepolymers and the polymercapto silicone monomers and / or prepolymers;(c) optionally cleaning the 3D object; and then(d) optionally heating the 3D object (e.g., at a temperature in a range of about 70°C to about 200°C) to volatilize and remove (e.g., partially, substantially, or completely remove) the non-reactive diluent when present.

18. The method of claim 17, wherein producing step (b) comprises providing a digital model of the 3D object; applying an iso-tropic volumetric scale factor to the 3D object sufficient to offset volumetric shrinkage due to solvent removal to produce a modified digital model; and then producing the 3D object using the modified digital model.

19. A three-dimensional object produced by the method of any one of claims 9-12.

20. A three-dimensional object produced by the method of claim 17 or claim 18.

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