WO2022066565A1 - Epoxy dual cure resin for the production of moisture-resistant articles by additive manufacturing - Google Patents

Abstract

A dual cure resin useful for the production of moisture-resistant objects by additive manufacturing is provided, said resin in some aspects comprising a mixture of: (a) a light-polymerizable component, said light polymerizable component comprising: (i) a light polymerizable monomer; (ii) a photoinitiator; and (iii) a dicyclopentadienyl (DCPD) (meth)acrylate reactive diluent; (b) a heat-polymerizable component, said heat-polymerizable component comprising: (i) an epoxy resin; (ii) a substituted or unsubstituted succinic anhydride or maleic anhydride curative; (iii) a core shell rubber toughener; and (iv) optionally, an epoxy-reactive toughening agent.

Description

EPOXY DUAL CURE RESIN FOR THE PRODUCTION OF MOISTURE- RESISTANT ARTICI.ES BY ADDITIVE MANUFACTU ING

Cross-reference to Related Applications

This application claims the benefit of U.S. Provisional Application No. 63/083,298, filed September 25, 2020, the contents of which is incorporated by reference herein in its entirety.

Field of the Invention

The present invention concerns resins and methods of use thereof in producing objects by additive manufacturing, particularly objects having good moisture resistance.

Background of the Invention

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.

The recent introduction of a more rapid stereolithography technique known as continuous liquid interface production (CLIP), coupled with the introduction of "dual cure" resins for additive manufacturing, has expanded the usefulness of stereolithography from prototyping to manufacturing See, e.g., US Patent Nos. 9,211,678; 9,205,601; and 9,216,546 to DeSimone et al.; and also J. Tumbleston, D. Shirvanyants, N. Ermoshkin et al., Continuous liquid interface production of 3D Objects, Science 347, 1349-1352 (2015); see also Rolland et al., US Patent Nos. 10,350,823; 10,155,882; 9,676,963, 9,453,142 and 9,598,606. Also note Das et al., High temperature three dimensional printing compositions, US Patent No. 9,708,761.

Together, these developments have created an increased demand for additive manufacturing resins and systems that allow for the production of objects with more diverse properties. Summary of the Invention

Provided herein according to some aspects is a dual cure resin useful for the production of moisture-resistant objects by additive manufacturing, said resin comprising a mixture of: (a) a light-polymerizable component, said light polymerizable component comprising: (i) a light polymerizable monomer; (ii) a photoinitiator; and (Hi) a dicyclopentadienyl (DCPD) (meth)acrylate reactive diluent; (b) a heat-polymerizable component, said heat-polymerizable component comprising: (i) an epoxy resin; (ii) a substituted or unsubstituted succinic anhydride or maleic anhydride curative; (Hi) a core shell rubber toughener; and (iv) optionally, an epoxy-reactive toughening agent.

In some embodiments, the reactive diluent has a structure of Formula (I):

wherein n is 1 or 2, R is hydrogen or methyl, and the dashed line is an optional double bond.

In some embodiments, the curative has a structure of Formula (II):

wherein the dashed line represents an optional double bond, and Ri and R2 are each independently selected hydrogen, aliphatic, aromatic, or mixed aliphatic and aromatic, groups, or Ri and R2 together form a bridging aliphatic, aromatic, or mixed aliphatic and aromatic, group.

In some embodiments, Ri and R2 together form a cycloalkane or bicycloalkane ring containing (with the succinic anhydride group to which it is fused) 5 to 8 carbon atoms, optionally substituted 1 or 2 times with independently selected C1-C4 alkyl. In some embodiments, the compound of Formula (II) comprises a polyanhydride (e.g., a dianhydride such as Bisphenol-A dianhydride (BisDA), a polymer adducted with maleic anhydride such as polybutadiene adducted with maleic anhydride, etc.).

In some embodiments, the light polymerizable monomer comprises a monofunctional or polyfunctional acrylate or a methacrylate (e.g., a urethane acrylate or methacrylate).

In some embodiments, the epoxy resin comprises an imide-epoxy, a dicyclopentadiene epoxy, a bisphenol A epoxy, a bisphenol F epoxy, a novolac epoxy, an aliphatic epoxy, a glycidylamine epoxy, an epoxidized vegetable oil, or a combination thereof.

In some embodiments, the core shell rubber toughener comprises a polybutadiene core.

In some embodiments, the epoxy-reactive toughening agent comprises a compound of Formula (III):

wherein: m is 1 or 2; n is 2 to 6;

R° is an n-valent radical of an elastomeric prepolymer (e.g., after the removal of the terminal isocyanate, amino or hydroxyl groups), the elastomeric prepolymer being soluble or dispersible in epoxy resin;

X and Y independently of one another are -O- or -NR³-, with at least one of X and Y being -NR³-;

R² is an m+l-valent radical of polyphenol or aminophenol after the removal of the phenolic hydroxyl group(s) and optionally of the amino group; and

R³ is hydrogen, C1-C6 alkyl, phenyl or phenol.

In some embodiments, the light-polymerizable component comprises: (i) a light polymerizable monomer (e.g., an acrylate or methacrylate); and (ii) a photoinitiator (e.g., phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (TPO)).

In some embodiments, the dual cure resin is homogeneous.

In some embodiments, the dual cure resin is nonaqueous. Also provided is a method of making a three-dimensional object, comprising: (a) producing an intermediate three-dimensional object from a dual cure resin as taught herein by light polymerization of said resin in an additive manufacturing process; (b) optionally cleaning said intermediate object; and then (c) heating and/or microwave irradiating said intermediate three-dimensional object to produce said three-dimensional object.

In some embodiments, the additive manufacturing process comprises bottom-up stereolithography (e.g., continuous liquid interface production).

Further provided is a three-dimensional object produced by a process as taught herein.

The foregoing and other objects and aspects of the present invention are explained in greater detail in the specification set forth below. The disclosures of all United States patent references cited herein are to be incorporated herein by reference.

Detailed Description of Illustrative Embodiments

The present invention is now described more fully hereinafter. 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.

The terminology used herein is for the purpose of describing 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. 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.

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").

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. Well- known functions or constructions may not be described in detail for brevity and/or clarity.

1. RESINS.

Dual cure resins for additive manufacturing include a light reactive component and a second reactive component, typically a thermally cured component.

A. Light-polymerizable monomers and/or prepolymers. Sometimes also referred to as "Part A" of the resin, these are monomers and/or prepolymers that can be polymerized by exposure to actinic radiation or light. This resin can have a functionality of 2 or higher (though a resin with a functionality of 1 can also be used when the polymer does not dissolve in its monomer). A purpose of Part A is to "lock" the shape of the object being formed or create a scaffold for the one or more additional components (e.g., Part B). Importantly, Part A is present at or above the minimum quantity needed to maintain the shape of the object being formed after the initial solidification during photolithography. In some embodiments, this amount corresponds to less than ten, twenty, or thirty percent by weight of the total resin (polymerizable liquid) composition.

Examples of reactive end groups suitable for Part A constituents, monomers, or prepolymers include, but are not limited to: acrylates, methacrylates, a-olefins, N-vinyls, acrylamides, methacrylamides, styrenics, epoxides, thiols, 1,3 -dienes, vinyl halides, acrylonitriles, vinyl esters, maleimides, and vinyl ethers.

An aspect of the solidification of Part A is that it provides a scaffold in which a second reactive resin component, termed "Part B," can solidify during a second step, as discussed further below.

Light reactive components for dual cure resin are known and described in, for example, US Patent Nos. 9,676,963, 9,453,142 and 9,598,606 to Rolland et al., the disclosures of which are incorporated herein by reference. As a non-limiting example, the light reactive component may comprise urethane acrylate or urethane methacrylate.

DCPD (meth)acrylate reactive diluents. Reactive diluents for carrying out the present invention have, in some embodiments, a structure of Formula (I):

such as a structure of Formula (I)(a):

wherein n is 1 or 2, R is hydrogen or methyl, and the dashed line is an optional double bond.

Suitable examples of Formula (I) include, but are not limited to: dicyclopentanyl acrylate, having the structure:

(e.g., Hitachi Chemical FA-513 AS); dicyclopentenyl acrylate, having the structure:

e.g., Hitachi Chemical FA-5 HAS); and the methacrylate analogs thereof.

B. Heat-polymerizable monomers and/or prepolymers. Sometimes also referred to as "Part B" in the present invention, the thermally reactive component comprises an epoxy resin, and in some embodiments an epoxy-reactive toughening agent.

Any suitable epoxy resin can be used. In some embodiments, the epoxy resin comprises a bisphenol A epoxy resin, a bisphenol F epoxy resin, a novolac epoxy resin, an aliphatic epoxy resin, a glycidylamine epoxy resin, or a combination thereof. In some embodiments, the epoxy resin comprises an epoxy compound having at least two epoxy groups; in other embodiments epoxy resin can comprise an epoxy compound having a single epoxy group, for example as a reactive diluent. Numerous examples of suitable epoxy resins (and organic hardeners) are known. See, e.g., U.S. Pat. Nos. 3,945,972; 3,947,395; 4,833,226; 5,319,004; 6,355,763; 6,881,813; 8,383,025; 9,133,301; etc.

In some embodiments, the epoxy resin comprises an epoxidized vegetable oil. In general, epoxidized vegetable oils can be obtained by the epoxidation of triglycerides of unsaturated fatty acids. They are made by epoxidizing the reactive olefin groups of the naturally occurring triglyceride oils. The olefin groups can be epoxidized with peracids, such as perbenzoic, peracetic and the like, and with hydrogen peroxide. Suitable epoxidized vegetable oils are epoxidized linseed oil, epoxidized soybean oil, epoxidized corn oil, epoxidized cottonseed oil, epoxidized perilla oil, epoxidized safflower oil, etc. See, e.g., U.S. Pat. Nos. 3,051,671; 5,973,082; 8,481,622; 9,169,386; 10,350,823; 10,155,882; see also M. Stemmelen et al., A fully biobased epoxy resin from vegetable oils: From the synthesis of the precursors by thiol-ene reaction to the study of the final material, J. Polym Sci. Part A: Polym Chem. 49, 2434-2444 (2011).

In some embodiments, the epoxy resin comprises a catalyzed epoxy resin (which may not require a hardener). In such case, the resin may further include an epoxy homopolymerization catalyst, such as a tertiary amine or imidizole (anionic polymerization) or boron trifluoride (cationic polymerizations).

In one embodiment, the epoxy resin is a dicyclopentadiene-containing polyepoxide. Suitable examples include, but are not limited to, the epoxy resin Huntsman Tactix® 556 or 756 (Huntsman Corporation, The Woodlands, Texas, U.S.A.), Nippon Kayaku XD-1000 (Nippon Kayaku Co., Ltd., Tokyo, Japan), and a DIC HP-7200 series resin (DIC Corporation, Tokyo, Japan). See, e.g., US Patent No. 8,258,216 to Park Electrochemical.

Anhydride curative. In some embodiments, the anhydride curative has a structure of Formula (II):

wherein the dashed line represents an optional double bond, and Ri and R2 are each independently selected hydrogen, aliphatic, aromatic, or mixed aliphatic and aromatic, groups (which may be substituted or unsubstituted and may optionally contain heteroatoms such as N, O, or S), or Ri and R2 together form a bridging aliphatic, aromatic, or mixed aliphatic and aromatic, group (which may be substituted or unsubstituted and may optionally contain heteroatoms such as N, O, or S). Such groups may include, for example, aliphatic groups such as alkyl, alkenyl, alkynyl, cycloalkyl (such as cycloalkane); and/or aromatic groups such as aryl.

"Alkyl" as used herein refers to a straight or branched chain hydrocarbon containing from 1 to 10 carbon atoms. Representative examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 3 -methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n- heptyl, n-octyl, n-nonyl, n-decyl, and the like. "Loweralkyl" as used herein is a subset of alkyl, in some embodiments preferred, and refers to a straight or branched chain hydrocarbon group containing from 1 to 4 carbon atoms (C1-C4). Representative examples of lower alkyl include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tertbutyl, and the like.

"Alkenyl" as used herein refers to a straight or branched chain hydrocarbon containing from 1 to 10 carbon atoms (or in loweralkenyl 1 to 4 carbon atoms) which include 1 to 4 double bonds in the normal chain. Representative examples of alkenyl include, but are not limited to, vinyl, 2-propenyl, 3-butenyl, 2-butenyl, 4-pentenyl, 3 -pentenyl, 2-hexenyl, 3- hexenyl, 2,4-heptadiene, and the like.

"Alkynyl" as used herein alone or as part of another group, refers to a straight or branched chain hydrocarbon containing from 1 to 10 carbon atoms (or in loweralkynyl 1 to 4 carbon atoms) which include 1 triple bond in the normal chain. Representative examples of alkynyl include, but are not limited to, 2-propynyl, 3-butynyl, 2-butynyl, 4-pentynyl, 3- pentynyl, and the like.

In some embodiments of the foregoing, Ri and R2 together form a cycloalkyl or bicycloalkyl ring containing (with the succinic anhydride group to which it is fused) 5 to 8 carbon atoms, optionally substituted 1 or 2 times (e.g., with independently selected C1-C4 alkyl).

"Cycloalkyl" as used herein alone or as part of another group, refers to a saturated or partially unsaturated cyclic hydrocarbon group containing from 3, 4 or 5 to 6, 7 or 8 carbons. Representative examples of cycloalkyl include, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. These rings may be optionally substituted with additional substituents as described herein such loweralkyl.

In some embodiments of the foregoing, Ri and R2 together form a cycloalkane or bicycloalkane ring containing (with the succinic anhydride group to which it is fused) 5 to 8 carbon atoms, optionally substituted 1 or 2 times (e.g., with independently selected C1-C4 alkyl).

"Cycloalkane" as used herein alone or as part of another group, refers to a saturated cyclic hydrocarbon group containing from 3, 4 or 5 to 6, 7 or 8 carbons, optionally with bridging atoms. Representative examples of cycloalkyl include, for example, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.

For example, in some embodiments, the compound of Formula (II) is:

Suitable anhydrides include but are not limited to those available from Huntsman Chemical Company (e.g., Huntsman HY 1102).

In some embodiments of the foregoing, Ri and R2 together form an aryl containing (with the maleic anhydride group to which it is fused) 5 to 8 carbon atoms, optionally substituted 1 or 2 times (e.g., with independently selected C1-C4 alkyl).

"Aryl" as used herein alone or as part of another group, refers to a monocyclic carbocyclic ring system or a bicyclic carbocyclic fused ring system having one or more aromatic rings. Representative examples of aryl include, azulenyl, indanyl, indenyl, naphthyl, phenyl, tetrahydronaphthyl, and the like.

In some embodiments, the compound of Formula (II) comprises a polyanhydride. For example, in some embodiments, the compound of Formula (II) comprises a bisphenol-A dianhydride (BisDA), having the structure:

such as available from Saudi Basic Industries Corporation (SABIC). Another non-limiting example of such a a polyanhydride is a polybutadiene adducted with maleic anhydride, such as a compound of the structure:

wherein m, n, o and p are integers selected to give a molecular weight Mn for said compound of from 1,000 or 2,000 to 4,000 or 5,000, or more (e.g., Ricon® 130MA8 polybutadiene adducted with maleic anhydride, available from Cray Valley USA, LLC, Oaklands Corporate Center, 468 Thomas Jones Way, Suite 100, Exton, PA 19341 USA).

Tougheners. In one embodiment, the epoxy-reactive toughening agent is a compound of Formula III:

wherein: m is 1 or 2, n is 2 to 6,

R° is an n-valent radical of an elastomeric prepolymer (e.g., after the removal of the terminal isocyanate, amino or hydroxyl groups), the elastomeric prepolymer being soluble or dispersible in epoxy resin,

X and Y are each independently -O- or -NR³-, with at least one of X or Y being -NR³-,

R² is an m+l-valent radical of polyphenol or aminophenol after the removal of the phenolic hydroxyl group(s) and optionally of the amino group, and

R³ is hydrogen, Ci-Ce alkyl, phenyl or phenol (See, e.g., US Patent No. 9,416,271 to Huntsman) (and a detailed description of the toughening agent of formula (I) is given in U.S. Pat. No. 5,278,257, column 4, line 20 to column 16, line 20, the disclosure of which is incorporated herein by reference). An example of a toughening agent is Flexibilizer DY 965 (available from Huntsman Advanced Materials Americas LLC, prepared according to Example 16 of U.S. Pat. No. 5,278,257).

C. Additional resin ingredients. Photoinitiators included in the polymerizable liquid (resin) can be any suitable photoinitiator including type I and type II photoinitiators and including commonly used UV photoinitiators, examples of which include but are not limited to phosphine oxides such as diphenly(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), ethyl(2,4,6-trimehtylbenzoyl) phenylphosphinate (TPO-L), ethyl(3-benzoyl-2,4,6-trimethylbenzoyl)(phenyl)phosphinate (XKm); aminoacetophenones such as 2-benzyl-2-dimethylamino-4- morpholinobutyrophenone (BDMB); benzophenones such as 4-benzoyl-4'-methyldiphenyl sulphide (BMS) and 4,4'-bis(diethylamino)benzophenone (EMK); thioxanthones such as 2- isopropylthi oxanthone (ITX) and 2,4-diethylthioxanthone (DETX); ketocoumarins; acetophenones; such as diethoxyacetophenone; alpha hydroxy ketones such as 1- hydroxycyclohexyl phenyl-ketone and oligo[2-hydroxy-2-methyl-l-[4-(l- methylvinyl)vinyl)phenyl]propane; and their polymeric derivatives. Note also that, in addition to the resins described herein, these photoinitiators can be used in any of the single cure resins set forth in US Patent Nos. 9,211,678, 9,205,601, and 9,216,546 to DeSimone et al., and in any of the dual cure resins described in US Patent Nos. 9,676,963, 9,453,142 and 9,598,606 to Rolland et al., the disclosures of which are hereby incorporated by reference herein in their entirety.

The liquid resin or polymerizable material can have solid particles suspended or dispersed therein. Any suitable solid particle can be used, depending upon the end product being fabricated. 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 solubilized in the liquid resin as also discussed below. For example, magnetic or paramagnetic particles or nanoparticles can be employed. The liquid resin can have additional ingredients solubilized therein, including pigments, dyes, active compounds or pharmaceutical compounds, detectable compounds (e.g., fluorescent, phosphorescent, radioactive), etc., 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.

Chain extenders. In some embodiments, chain extenders may include those that can react with epoxides to grow linear chains. Particular examples include, but are not limited to, dihydric phenolic compounds such as bisphenol A, bisphenol S (4,4'-sulfonyldiphenol), bisphenol K, tetrabromobisphenol A, etc. See U.S. Patent No. 4,594,219 to Berthram et al.

Chain extender catalysts. In some embodiments, chain extender catalysts may include those that catalyze or promote the reaction of dihydric phenolic chain extenders with epoxides to grow linear chains. Examples of chain extender catalysts include, but are not limited to, onium salts, preferably phosphonium salts, and even more preferably phosphonium halides (e.g., tetrabutylphosphonium bromide, ethyl triphenylphosphonium iodide, etc.). See U.S. Patent Nos. 4,767,832; 4,352,918; and 3,477,990, the disclosures of which are incorporated herein by reference. In some embodiments, the amount of the catalyst used may be from 0.01 to 10 percent, preferably from 0.05 to 5 percent, or from 0.1 to 2 percent, by weight of the composition.

Dyes/non-reactive light absorbers. In some embodiments, polymerizable liquids for carrying out the present invention 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 (Hi) an organic ultraviolet light absorber such as a hydroxybenzophenone, hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone, hydroxypenyltriazine, 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 US Patent Nos. 3,213,058; 6,916,867; 7,157,586; and 7,695,643, the disclosures of which are incorporated herein by reference.

Fillers. 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 all of the foregoing. Suitable fillers include tougheners, such as core-shell rubbers, as discussed below.

Tougheners. 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 silsesqui oxanes (POSS), carbonaceous materials (e.g., carbon black, carbon nanotubes, carbon nanofibers, fullerenes), ceramics and silicon carbides, with or without surface modification or functionalization.

Core-shell rubbers. Core-shell rubbers are particulate materials (particles) having a rubbery core (e.g., polybutadiene). Such materials are known and described in, for example, US Patent Application Publication No. 20150184039, as well as US Patent Application Publication No. 20150240113, and US Patent 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 (/.< ., 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 136, Kaneka Kane Ace MX 137, Kaneka Kane Ace MX 153, Kaneka Kane Ace MX 154, Kaneka Kane Ace MX 156, Kaneka Kane Ace MX170, Kaneka Kane Ace MX 257 and Kaneka Kane Ace MX 120 core-shell rubber dispersions, and mixtures thereof, and those sold by Dow under the designation Parloid. Organic diluents. Diluents for use in the present invention are preferably reactive organic diluents; that is, diluents that will degrade, isomerize, cross-react, or polymerize, with themselves or a light polymerizable component, during the additive manufacturing step. In general, the diluent(s) are included in an amount sufficient to reduce the viscosity of the polymerizable liquid or resin (e.g., to not more than 6,000, 5,000, 4,000, or 3,000 centipoise at 25 degrees Centigrade. The diluent may be included in the polymerizable liquid in any suitable amount, typically from 1, 5 or 10 percent by weight, up to about 30 or 40 percent by weight, or more.

2. METHODS OF USE, AND PRODUCTS.

Techniques for producing an intermediate object, or “green” intermediate, from such resins by additive manufacturing are known. Suitable techniques include bottom-up and top- down additive manufacturing, generally known as stereolithography. Such methods are known and described in, for example, U.S. Patent No. 5,236,637 to Hull, US Patent Nos. 5,391,072 and 5,529,473 to Lawton, U.S. Patent No. 7,438,846 to John, US Patent No. 7,892,474 to Shkolnik, U.S. Patent 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. The disclosures of these patents and applications are incorporated by reference herein in their entirety.

In some embodiments, the additive manufacturing step is carried out by one of the family of methods sometimes referred to as continuous liquid interface production (CLIP). CLIP is known and described in, for example, US Patent Nos. 9,211,678; 9,205,601; 9,216,546; and others; in J. Tumbleston et al., Continuous liquid interface production of 3D Objects, Science 347, 1349-1352 (2015); and in R. Janusziewcz et al., Layerless fabrication with continuous liquid interface production, Proc. Natl. Acad. Sci. USA 113, 11703-11708 (2016). Other examples of methods and apparatus for carrying out particular embodiments of CLIP include, but are not limited to: Batchelder et al., US Patent Application Pub. No. US 2017/0129169; Sun and Lichkus, US Patent Application Pub. No. US 2016/0288376; Willis et al., US Patent Application Pub. No. US 2015/0360419; Lin et al., US Patent Application Pub. No. US 2015/0331402; D. Castanon, US Patent Application Pub. No. US 2017/0129167. B. Feller, US Pat App. Pub. No. US 2018/0243976; M. Panzer and J. Tumbleston, US Pat App Pub. No. US 2018/0126630; and K. Willis and B. Adzima, US Pat App Pub. No. US 2018/0290374. Once the intermediate object has been formed and optionally cleaned (e.g., by wiping, blowing, spinning, washing, etc.), the object is then further cured, such as by heating. Heating may be active heating (e.g., baking in an oven, such as an electric, gas, solar oven or microwave oven, or combination thereof), or passive heating (e.g., at ambient (room) temperature). Active heating will generally be more rapid than passive heating and is typically preferred, but passive heating — such as simply maintaining the intermediate at ambient temperature for a sufficient time to effect further cure — may in some embodiments also be employed.

In some embodiments, the three-dimensional object produced as taught herein may have a higher heat deflection temperature (HDT) and/or toughness. For example, the object may have a heat deflection temperature of from 150 or 160 °C, to 200, 250, or 300 °C or more, and/or a Notched Izod Impact Strength of at least 40 or 45 J/m, to 70 or 100 J/m or more. In some embodiments, the HDT may be tested on DMA Q800, 3 point bending, ramp rate - 5°C/min, 0.455 MPa, 25°C to 250°C sweep, Sample Size- L = 20mm, W= 10mm, T=2mm. In some embodiments, the Notched Izod Impact may be tested by ASTM D256, 3.2mm thick sample.

In some embodiments, the three-dimensional object produced as taught herein may have improved moisture resistence. For example, the object may absorb not more than 2, 3, 4 or 5 percent by weight of water after being immersed in deionized water at atmospheric pressure and a temperature of 85°C for a time of eight days. In some embodiments, the improved moisture resistence is in addition to the higher HDT and/or toughness.

The present invention is further described in the following non-limiting examples.

EXAMPLE 1

Photonetwork Cured with Varying Diluents

Three grams of commercially available bisphenol A diacrylate (SR601), seven grams of a monofunctional, photoreactive diluent with varying glass transition temperatures (N,N- dimethylacrylaminde [DMAA], cycloaliphatic acrylate [SR217], or di cyclopentadienyl acrylate [FA-513 AS]), and 0.08 grams of phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide were mixed in a planetary centrifugal mixer to yield a homogeneous resin. Resin was cast into a rectangular mold (30mm xlOmm x 1mm) and flood cured for 20 seconds under 382 nm light at an intensity of 25 mW/cm². Samples were removed from the mold, and water uptake was monitored by measuring the mass prior to and following submersion in deionized water for 10 days at 40 °C. Results are given in Table 1.

COMPARATIVE

EXAMPLE A

Epoxy Cured with Amine

Twenty one grams of a commercially available urethane acrylate (CN983), 39 grams of a Kaneka Kane Ace® MX 153 33% concentrate core shell rubber (CSR) toughening agent 5 in a bisphenol-A epoxy resin, 14 grams of 3,3 diamino diphenyl sulphone, and 0.84 grams of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide were mixed with 25 grams of N,N’- dimethylacrylamide in a planetary centrifugal mixer to yield a homogeneous resin. This resin was formed into a three-dimensional intermediate using continuous liquid interface production (CLIP) in continuous exposure mode, using a 385 nm LED projector with a light intensity of 9 mW/cm2 at a speed of 30 mm/hour. The formed material was cured in a convection oven at temperatures up to 220°C to yield the desired product. The mechanical properties of dual cure products produced from such resins were evaluated by producing mechanical test samples in this manner, and results are given in Table 2 below.

EXAMPLE 2

Epoxy Cured with the Anhydride

Fifteen grams of a commercially available epoxy acrylate (Genomer 2281), 36.5 grams of a Kaneka Kane Ace® MX 153 33% concentrate core shell rubber (CSR) toughening agent in a bisphenol-A epoxy resin, 13.5 grams of methyl hexahydrophtalic anhydride, 1 gram of 1-ethylimidiazole (catalyst) and 0.84 grams of phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide were mixed with 35 grams of N,N’ -dimethylacrylamide in a planetary centrifugal mixer to yield a homogeneous resin. This resin was formed into a three- dimensional intermediate using continuous liquid interface production (CLIP) in continuous exposure mode, using a 385 nm LED projector with a light intensity of 9 mW/cm2 at a speed of 28 mm/hour. The formed material was cured in a convection oven at temperatures up to 220°C to yield the desired product. The mechanical properties of dual cure products produced from such resins were evaluated by producing mechanical test samples in this manner, and results are given in Table 2 below.

EXAMPLE 3

Epoxy Cured with Anhydride with Photo-network using DicycloDentadienyl acrylate

Fifteen grams of a commercially available epoxy acrylate (Genomer 2281), 36.5 grams of a Kaneka Kane Ace® MX 153 33% concentrate core shell rubber (CSR) toughening agent in a bisphenol-A epoxy resin, 13.5 grams of Methyl hexahydrophtalic anhydride, 1 gram of 1-ethylimidiazole and 0.84 grams of phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide were mixed with 35 grams of Dicyclopentadienyl acrylate (FA-513 AS) in a planetary centrifugal mixer to yield a homogeneous resin. This resin was formed into a three- dimensional intermediate using continuous liquid interface production (CLIP) in continuous exposure mode, using a 385 nm LED projector with a light intensity of 9 mW/cm2 at a speed of 32 mm/hour. The formed material was cured in a convection oven at temperatures up to 220°C to yield the desired product. The mechanical properties of dual cure products produced from such resins were evaluated by producing mechanical test samples in this manner, and results are given in Table 2 below.

EXAMPLE 4

Epoxy Cured with Multiple Anhydrides and Photo-network using Dicyclopentadienyl acrylate

Sixteen grams of a commercially available urethane methacrylate (Esstech X-851), 41.6 grams of a Kaneka Kane Ace® MX 153 33% concentrate core shell rubber (CSR) toughening agent in a bisphenol-A epoxy resin, 6 grams of methyl hexahydrophtalic anhydride (MHA), 6 grams of nadic methyl anhydride (NMA), 0.90 gram of 1- ethylimidiazole and 0.90 grams of phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide were mixed with 37.6 grams of dicyclopentadienyl acrylate (FA-513 AS) in a planetary centrifugal mixer to yield a homogeneous resin. This resin was formed into a three-dimensional intermediate using a Carbon, Inc. additive manufacturing apparatus carrying out continuous liquid interface production (CLIP) in continuous exposure mode, using a 385 nm LED projector with a light intensity of 9 mW/cm2 at a speed of 34 mm/hour. The formed material was cured in a convection oven at temperatures up to 220°C to yield the desired product. Formulations can be prepared such that 0-50 wt. % of the curative may contain an internal unsaturated group, such as in the nadic methyl anhydride (above) or methyltetrahydrophthalic anhydride (MTA). The thermomechanical properties of dual cure products produced from such resins were evaluated by producing thermomechanical test samples in this manner, and results are given in Table 3 below.

Photocuring kinetics were monitored using differential scanning calorimetry (DSC). Small quantities of pre-mixed samples as above were applied to silicon coated aluminum DSC pans at an approximate thickness of 150 microns and were exposed to 9 mW/cm² light UV light for 12 seconds. Conversion values were calculated relative to a theoretical maximum and are recorded in Table 3.

EXAMPLE 5

Dicyclopentadiene based Epoxy cured with Anhydride

Fifteen grams of a commercially available urethane methacrylate (X-851), 35 grams of a dicyclopentadiene based epoxy commercially available under XD-1000, 13.5 grams of methyl hexahydrophtalic anhydride, 1 gram of 1-ethylimidiazole and 0.84 grams of phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide were mixed with 35 grams of di cyclopentadienyl acrylate (FA-513 AS) in a planetary centrifugal mixer to yield a homogeneous resin. This resin was formed into a three-dimensional intermediate using continuous liquid interface production (CLIP) in continuous exposure mode, using a 385 nm LED projector with a light intensity of 9 mW/cm2 at a speed of 20 mm/hour. The formed material was cured in a convection oven at temperatures up to 220°C to yield the desired product. The mechanical properties of dual cure products produced from such resins were evaluated by producing mechanical test samples in this manner, and results are given in Table 4 below.

EXAMPLE 6

WHR-991S Epoxy Cured with Anhydride

Fifteen grams of a commercially available urethane methacrylate (SR 834), 22 grams of a rigid imide structure containing epoxy commercially available under WHR-991S (Nippon Kayaku Co., Ltd.) dissolved in 11 grams of difunctional glycidyl amine (GAN), 17 grams of methyl hexahydrophtalic anhydride, 1 gram of 1-ethylimidiazole and 0.84 grams of phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide were mixed with 35 grams of di cyclopentadienyl acrylate (FA-513 AS) in a planetary centrifugal mixer to yield a homogeneous resin. This resin was formed into a three-dimensional intermediate using continuous liquid interface production (CLIP) in continuous exposure mode, using a 385 nm LED projector with a light intensity of 9 mW/cm2 at a speed of 36 mm/hour. The formed material was cured in a convection oven at temperatures up to 220°C to yield the desired product. The mechanical properties of dual cure products produced from such resins were evaluated by producing mechanical test samples in this manner, and results are given in Table 4 below.

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 of the claims to be included therein.

Claims

WE CLAIM:

1. A dual cure resin useful for the production of moisture-resistant objects by additive manufacturing, said resin comprising a mixture of:

(a) a light-polymerizable component, said light polymerizable component comprising:

(i) a light polymerizable monomer;

(ii) a photoinitiator; and

(Hi) a dicyclopentadienyl (DCPD) (meth)acrylate reactive diluent;

(b) a heat-polymerizable component, said heat-polymerizable component comprising:

(i) an epoxy resin;

(ii) a substituted or unsubstituted succinic anhydride or maleic anhydride curative;

(Hi) a core shell rubber toughener; and

(iv) optionally, an epoxy-reactive toughening agent.

2. The dual cure resin of claim 1, wherein said reactive diluent has a structure of

Formula (I):

where n is 1 or 2, R is hydrogen or methyl, and the dashed line is an optional double bond.

3. The dual cure resin of claim 2, wherein said reactive diluent comprises dicyclopentanyl acrylate, having the structure:

or a methacrylate analog thereof.

4. The dual cure resin of claim 2, wherein said reactive diluent comprises dicyclopentenyl acrylate, having the structure:

or a methacrylate analog thereof.

5. The dual cure resin of any preceding claim, wherein said curative has a structure of Formula (II):

wherein the dashed line represents an optional double bond, and Ri and R2 are each independently selected hydrogen, aliphatic, aromatic, or mixed aliphatic and aromatic, groups, or Ri and R2 together form a bridging aliphatic, aromatic, or mixed aliphatic and aromatic, group.

6. The dual cure resin of claim 5, where Ri and R2 together form a cycloalkane or bicycloalkane ring containing (with the succinic anhydride group to which it is fused) 5 to 8 carbon atoms, optionally substituted 1 or 2 times with independently selected C1-C4 alkyl.

7. The dual cure resin of claim 5, wherein said compound of Formula (II) is selected from the group consisting of:

8. The dual cure resin of claim 5, wherein said compound of Formula (II) comprises a polyanhydride (e.g., a dianhydride such as Bisphenol-A dianhydride (BisDA), a polymer adducted with maleic anhydride such as polybutadiene adducted with maleic anhydride, etc.).

9. The dual cure resin of any preceding claim, wherein the light polymerizable monomer comprises a monofunctional or polyfunctional acrylate or a methacrylate (e.g., a urethane acrylate or methacrylate).

10. The dual cure resin of any preceding claim, wherein said epoxy resin comprises an imide-epoxy, a dicyclopentadiene epoxy, a bisphenol A epoxy, a bisphenol F epoxy, a novolac epoxy, an aliphatic epoxy, a glycidylamine epoxy, an epoxidized vegetable oil, or a combination thereof.

11. The dual cure resin of any preceding claim, wherein said core shell rubber toughener comprises a polybutadiene core.

12. The dual cure resin of any preceding claim, wherein said epoxy-reactive toughening agent when present comprises a compound of Formula (III):

wherein: m is 1 or 2; n is 2 to 6; R° is an n-valent radical of an elastomeric prepolymer (e.g., after the removal of the terminal isocyanate, amino or hydroxyl groups), the elastomeric prepolymer being soluble or dispersible in epoxy resin;

X and Y are each independently -O- or -NR³-, with at least one of X or Y being -NR³-;

R² is an m+l-valent radical of polyphenol or aminophenol after the removal of the phenolic hydroxyl group(s) and optionally of the amino group; and

R³ is hydrogen, Ci-Ce alkyl, phenyl or phenol.

13. The dual cure resin of any preceding claim, wherein said dual cure resin is homogeneous.

14. The dual cure resin of any preceding claim, wherein said dual cure resin is nonaqueous.

15. A method of making a three-dimensional object, comprising:

(a) producing an intermediate three-dimensional object from a dual cure resin of any preceding claim by light polymerization of said resin in an additive manufacturing process;

(b) optionally cleaning said intermediate object; and then

(c) heating and/or microwave irradiating said intermediate three-dimensional object to produce said three-dimensional object.

16. The method of claim 15, wherein said additive manufacturing process comprises bottom-up stereolithography.

17. The method of claim 15 or claim 16, said three-dimensional object absorbing not more than 2, 3, 4 or 5 percent by weight of water after being immersed in deionized water at atmospheric pressure and a temperature of 85 °C for a time of eight days.

18. A three-dimensional object produced by the method of any one of claims 15 to

17.