WO2020191690A1

WO2020191690A1 - Photo-curable compositions for additive manufacturing

Info

Publication number: WO2020191690A1
Application number: PCT/CN2019/080001
Authority: WO
Inventors: Chunfu Chen; Daoqiang Lu
Original assignee: Henkel Ag & Co. Kgaa; Henkel (China) Co., Ltd.
Priority date: 2019-03-28
Filing date: 2019-03-28
Publication date: 2020-10-01

Abstract

A photo-curable composition for use in additive manufacturing is presented. Said composition comprising: a) at least one epoxidized polyolefin which is characterized by a residual olefinic unsaturation of from 0.01 to 0.5 meq/g polymer and which is selected from the group consisting of epoxidized alicyclic polyolefin and epoxidized aliphatic polyolefin; optionally b) at least one epoxide compound which is distinct from the epoxidized polyolefin (a); c) at least one compound which has at least two reactive mercapto-groups per molecule; d) at least one free radical photoinitiator compound; and, e) at least one polyamine having at least two amine hydrogens reactive toward epoxide groups.

Description

PHOTO-CURABLE COMPOSITIONS FOR ADDITIVE MANUFACTURING

FIELD OF THE INVENTION

The present invention concerns materials for the fabrication of solid three-dimensional objects. More particularly, the present invention is concerned with photo-curable compositions which may be used in additive manufacturing processes to join or form solid, three-dimensional (3D) objects.

BACKGROUND OF THE INVENTION

In conventional additive manufacturing techniques, the construction of a three-dimensional object is performed in a step-wise or layer-by-layer manner. Commonly –and as described in inter alia US Patent No. 5,236,637 (Hull) -a given layer of photo-curable resin is laid down on either the top surface or the bottom surface of a growing object and then solidified under the action of either visible, infrared or UV light irradiation or under an electron beam.

The photocurable resin used to form the or each layer of the object will contain monomers, oligomers, fillers and additives such as photoinitiators, blockers and colorants depending on the targeted properties of the resin. And photo-curable compositions based on epoxide compounds are known in the art.

WO2017/044381 (Carbon 3D Inc. ) describes an epoxy dual cure resin useful for additive manufacturing of three-dimensional objects, which composition includes: (i) a photoinitiator; (ii) monomers and/or prepolymers that are polymerizable by exposure to actinic radiation or light; (iii) optionally, a light absorbing pigment or dye; (iv) an epoxy resin; (v) optionally an organic hardener co-polymerizable with the epoxy resin; (vi) optionally a dual reactive compound having substituted thereon a first reactive group reactive with said monomers and/or prepolymers that are polymerizable by exposure to actinic radiation or light, and a second reactive group reactive with said epoxy resin (e.g., an epoxy acrylate) ; (vii) optionally a diluent; (viii) optionally a filler; and, (ix) optionally, a co-monomer and/or a co-prepolymer.

JP-A-2002-256062 (Teijin Seiki Co. Ltd) provides an active-energy ray curing resin composition composed of: cationically polymerizable organic compound of which at least a part is constituted by a diepoxy compound (a) ; a radical-polymerizing organic compound (b) ; an active-energy ray sensitive cation polymerizing initiator (c) ; and, an active-energy ray sensitive radical polymerizing initiator (d) .

JP-A-2017-007116 (Kao Corporation) provides a photocurable composition for three-dimensional molding containing: A) a photocurable resin precursor; and, B) a fine cellulose fiber and/or a modified article thereof having a number average fiber diameter of 0.5 nm to 200 nm and carboxyl group content of 0.1 mmol/g or more.

One recognized challenge with photo-curable compositions is ensuring that curing proceeds to the appropriate degree at both the surface and the interior of the 3D object or each layer thereof. For example, if the 3D object is cured completely (100%) during the 3D printing process, the interlayer adhesion can be too weak and the print may fail. In addition, the fully cured material may stick to parts of the printing apparatus and not release properly there from. Hence, it is often desirable to cure only in the range of from (5%to 99%and not to 100%during the printing process.

Subsequent to the printing process, uncured resin needs to be removed from the surface of the printing apparatus and the remaining resin cured at an accelerated rate. The uncured liquid resin disposed on the surface of the printed 3D object can often be removed by washing with an appropriate solvent. However, uncured liquid resin within the printed 3D object cannot be so removed and yet is undesirable: uncured liquid resin containing reactive compounds can leak from the printed 3D object and may be of health concern; uncured liquid resin containing reactive compounds is also problematic in applications of the 3D object where chemical inertness is paramount; and, such uncured liquid resin can deleteriously impact the mechanical performance of the 3D object, principally through softening of the 3D object.

There is considered to be a need in the art to develop novel formulations which can be utilized in additive manufacturing processes and which have curing profiles –in particular dual curing profiles -which can ameliorate or remove the above mentioned problems.

STATEMENT OF THE INVENTION

In accordance with a first aspect of the present invention there is provided a photo-curable composition for use in additive manufacturing, said composition comprising:

a) at least one epoxidized polyolefin which is characterized by a residual olefinic unsaturation of from 0.01 to 0.5 meq/g polymer and which is selected from the group consisting of epoxidized alicyclic polyolefin and epoxidized aliphatic polyolefin;

optionally b) at least one epoxide compound which is distinct from the epoxidized polyolefin (a) ;

c) at least one compound which has at least two reactive mercapto-groups per molecule;

d) at least one free radical photoinitiator compound; and,

e) at least one polyamine having at least two amine hydrogens reactive toward epoxide groups.

The composition as defined herein above and in the appended claims exhibits good surface light curability when disposed as layer or coating upon a substrate. Subsequent to the irradiation necessary to initiate its curing, the composition can be fully cured either under ambient conditions or by heating, dependent upon the selection of the epoxide compounds (a) , b) ) and the curatives (c) , e) ) . The cured compositions show operable mechanical properties which enables their use in deriving complex three dimensional objects by additive manufacturing.

Typically, the composition will comprise from 5 to 90 wt. and preferably from 10 to 80 wt. %, based on the total weight of the composition, of a) said at least one epoxidized polyolefin. Independently of, or supplemental to this condition, said at least one epoxidized polyolefin should typically be further characterized by an epoxy oxygen content of from 5 to 10 percent by weight, an epoxy equivalent weight of 100 to 2,000 g/eq. and a hydroxyl group content of from 1 to 3 percent by weight. Moreover, it is preferred that said at least one epoxidized polyolefin be further characterized by a number average molecular weight (Mn) of from 1000 to 10000 g/mol.

Whilst component b) of the composition is nominally optional, it is preferably present therein in an amount up to 80 wt. %, for example up to 70 wt. %, based on the weight of the composition. A preference may be noted for the inclusion in the composition, as at least a part of said component b) , of a polyepoxide compound having an epoxy equivalent weight of from 100 to 700 g/eq.

Good results have been obtained, wherein the free radical photoinitiator d) is selected from the group consisting of: benzoylphosphine oxides; aryl ketones; benzophenones; hydroxylated ketones; 1-hydroxyphenyl ketones; ketals; metallocenes; and combinations thereof. In particular, said free radical photoinitiator d) should be selected from the group consisting of: benzoin dimethyl ether; 1-hydroxycyclohexyl phenyl ketone; benzophenone; 4-chlorobenzophenone; 4-methylbenzophenone; 4-phenylbenzophenone; 4, 4'-bis (diethylamino) benzophenone; 4, 4'-bis (N, N'-dimethylamino) benzophenone (Michler's ketone) ; isopropylthioxanthone; 2-hydroxy-2-methylpropiophenone; 2-methyl-4- (methylthio) -2-morpholinopropiophenone; methyl phenylglyoxylate; methyl 2-benzoylbenzoate; 2-ethylhexyl 4- (dimethylamino) benzoate; ethyl 4- (N, N-dimethylamino) benzoate; phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide; diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide; ethyl phenyl (2, 4, 6-trimethylbenzoyl) phosphinate; and, combinations thereof.

It is further preferred that the composition as defined herein above comprises as component e) at least one polyamine containing primary and /or secondary amine groups and has an equivalent weight per primary or secondary amine group of not more than 150, preferably not more than 125.

The composition as a whole may desirably be characterized by a molar ratio of epoxy-reactive groups to epoxy groups from 0.95: 1 to 1.5: 1, preferably from 0.95: 1 to 1.1: 1.

In accordance with a second aspect of the present invention, there is provided a method for forming a three dimensional object, said method comprising:

i) providing a carrier and an optically transparent member having a movable build surface, said carrier and build surface defining a build region there between;

ii) within said build region, applying by 3D printing a first layer of the composition as defined herein above and in the appended claims;

iii) irradiating said build region through said optically transparent member to at least partially cure that first layer;

iv) applying a subsequent layer of said composition as defined herein above and in the appended claims by 3D printing on the at least partially cured layer; and,

v) irradiating said build region through said optically transparent member to at least partially cure that subsequent layer.

In an embodiment thereof, there is provided an iterative method for forming a three dimensional object, wherein said steps iv) and v) as defined above are performed and repeated so as to dispose second, third, fourth and further layers within the build region.

It will be recognized that the recited build surface may be moved away from the carrier to maintain a suitable build region for the application of the defined composition. The build surface and the formed layers of at least partially cured composition provide the scaffold on which subsequent layers may be disposed: the provision of further support means is not precluded, however, and can be applied at an appropriate time to maintain the integrity of an intermediate and /or final three dimensional object. That final object may be separated from all supporting media and further processed, if necessary.

In accordance with a third aspect of the invention there is provided a three dimensional object obtained in accordance with the method defined herein above and in the appended claims.

DEFINITIONS

As used herein, the singular forms "a" , "an" and "the" include plural referents unless the context clearly dictates otherwise.

The terms “comprising” , “comprises” and “comprised of” as used herein are synonymous with “including” , “includes” , “containing” or “contains” , and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps.

When amounts, concentrations, dimensions and other parameters are expressed in the form of a range, a preferable range, an upper limit value, a lower limit value or preferable upper and limit values, it should be understood that any ranges obtainable by combining any upper limit or preferable value with any lower limit or preferable value are also specifically disclosed, irrespective of whether the obtained ranges are clearly mentioned in the context.

The words "preferred" , "preferably" , “desirably” and “particularly” are used frequently herein to refer to embodiments of the disclosure that may afford particular benefits, under certain circumstances. However, the recitation of one or more preferable, preferred, desirable or particular embodiments does not imply that other embodiments are not useful and is not intended to exclude those other embodiments from the scope of the disclosure.

As used throughout this application, the word “may” is used in a permissive sense –that is meaning to have the potential to -rather than in the mandatory sense.

The term "additive manufacturing" as used herein refers to methods of joining or shaping materials by which objects are built from 3D-model data, usually layer-upon-layer; it may be contrasted with subtractive manufacturing technologies. The term "3D-printing" is often used as a synonym for additive manufacturing. Conventionally, a digital model of the object is generated using known modeling methods, including Computer Aided Design (CAD) programs: the digital model is divided into units in which each unit indicates where the material should be located in a layer. The individual units are sent to an additive manufacturing system or 3D printer which deposits the material according to the individual units and generates the complete three-dimensional object layer by layer. The disclosure of ASTM52900-15 or, where appropriate, the updated version of said Standard may here be instructive.

As used herein, the term " (co) polymer" includes homopolymers, copolymers, block copolymers and terpolymers.

As used herein, the term "epoxide" denotes a compound characterized by the presence of at least one cyclic ether group, namely one wherein an ether oxygen atom is attached to two adjacent carbon atoms thereby forming a cyclic structure. The term is intended to encompass monoepoxide compounds, polyepoxide compounds (having two or more epoxide groups) and epoxide terminated prepolymers. The term “monoepoxide compound” is meant to denote epoxide compounds having one epoxy group. The term “polyepoxide compound” is meant to denote epoxide compounds having at least two epoxy groups. The term “diepoxide compound” is meant to denote epoxide compounds having two epoxy groups.

The epoxide may be unsubstituted but may also be inertly substituted. Exemplary inert substituents include chlorine, bromine, fluorine and phenyl.

As used herein, “epoxy equivalent weight” means that weight of resin, in grams, that contains one equivalent of epoxy. The number of epoxide groups in the epoxide compound is determined by heating a weighted sample of the compound with an excess of 0.2 N pyridinium chloride in chloroform solution at the boiling point under reflux for two hours whereby the pyridinium chloride hydrochlorinates the epoxy groups to the chlorohydrin groups. After cooling, the excess pyridinium chloride is backtitrated with 0.1 N sodium hydroxide in methanol to the phenolphthalein and point. Reference is made to: ASTM D1652-11 Standard Test Method for Epoxy Content of Epoxy Resins.

The term “aliphatic” as used herein means a straight or branched, saturated or unsaturated hydrocarbon group. Aliphatic includes alkyl groups, alkenyl groups, and alkynyl groups.

The term “alicyclic” as used herein refers to compounds which combine the properties of aliphatic and cyclic compounds and include, but are not limited, to monocyclic or polycyclic aliphatic hydrocarbons and bridged cycloalkyl compounds, which are optionally substituted with one or more functional groups. As will be appreciated by the skilled reader, “alicyclic” is intended herein to include, but not to be limited to, cycloalkyl, cycloalkenyl, and cycloalkynyl moieties, which are optionally substituted with one or more functional groups. Illustrative alicyclic groups, which may optionally bear one or more substitutents, include: cyclopropyl; -CH ₂-cyclopropyl; cyclobutyl; -CH ₂-cyclobutyl, cyclopentyl; -CH ₂-cyclopentyl; cyclohexyl; -CH ₂-cyclohexyl; cyclohexenylethyl; cyclohexanylethyl; and, norbornyl.

As used herein, "C ₁-C _n alkyl" group refers to a monovalent group that contains 1 to n carbons atoms, that is a radical of an alkane and includes straight-chain and branched organic groups. As such, a "C ₁-C ₃₀ alkyl" group refers to a monovalent group that contains from 1 to 30 carbons atoms, that is a radical of an alkane and includes straight-chain and branched organic groups. Examples of alkyl groups include, but are not limited to: methyl; ethyl; propyl; isopropyl; n-butyl; isobutyl; sec-butyl; tert-butyl; n-pentyl; n-hexyl; n-heptyl; and, 2-ethylhexyl. In the present invention, such alkyl groups may be unsubstituted or may be substituted with one or more substituents such as halo, nitro, cyano, amido, amino, sulfonyl, sulfinyl, sulfanyl, sulfoxy, urea, thiourea, sulfamoyl, sulfamide and hydroxy. The halogenated derivatives of the exemplary hydrocarbon radicals listed above might, in particular, be mentioned as examples of suitable substituted alkyl groups. In general, however, a preference for unsubstituted alkyl groups containing from 1-18 carbon atoms (C ₁-C ₁₈ alkyl) -for example unsubstituted alkyl groups containing from 1 to 12 carbon atoms (C ₁-C ₁₂ alkyl) -should be noted.

The term “C ₃ –C ₃₀ cycloalkyl” is understood to mean a saturated, mono-, bi-or tricyclic hydrocarbon group having from 3 to 30 carbon atoms. In general, a preference for cycloalkyl groups containing from 3-18 carbon atoms (C ₃-C ₁₈ cycloalkyl groups) should be noted. Examples of cycloalkyl groups include: cyclopropyl; cyclobutyl; cyclopentyl; cyclohexyl; cycloheptyl; cyclooctyl; adamantane; and, norbornane.

As used herein, an “C ₆-C ₁₈ aryl” group used alone or as part of a larger moiety -as in “aralkyl group” -refers to optionally substituted, monocyclic, bicyclic and tricyclic ring systems in which the monocyclic ring system is aromatic or at least one of the rings in a bicyclic or tricyclic ring system is aromatic. The bicyclic and tricyclic ring systems include benzofused 2-3 membered carbocyclic rings. Exemplary aryl groups include: phenyl; indenyl; naphthalenyl, tetrahydronaphthyl, tetrahydroindenyl; tetrahydroanthracenyl; and, anthracenyl. And a preference for phenyl groups may be noted.

As used herein, "C ₂-C ₁₂ alkenyl" refers to hydrocarbyl groups having from 2 to 12 carbon atoms and at least one unit of ethylenic unsaturation. The alkenyl group can be straight chained, branched or cyclic and may optionally be substituted. The term “alkenyl” also encompasses radicals having “cis” and “trans” configurations, or alternatively, “E” and “Z” configurations, as appreciated by those of ordinary skill in the art. In general, however, a preference for unsubstituted alkenyl groups containing from 2 to 10 (C _2-10) or 2 to 8 (C _2-8) carbon atoms should be noted. Examples of said C ₂-C ₁₂ alkenyl groups include, but are not limited to: -CH=CH ₂; -CH=CHCH ₃; -CH ₂CH=CH ₂; -C (=CH ₂) (CH ₃) ; -CH=CHCH ₂CH ₃; -CH ₂CH=CHCH ₃; -CH ₂CH ₂CH=CH ₂; -CH=C (CH ₃) ₂; -CH ₂C (=CH ₂) (CH ₃) ; -C (=CH ₂) CH ₂CH ₃; -C (CH ₃) =CHCH ₃; -C (CH ₃) CH=CH ₂; -CH=CHCH ₂CH ₂CH ₃; -CH ₂CH=CHCH ₂CH ₃; -CH ₂CH ₂CH=CHCH ₃; -CH ₂CH ₂CH ₂CH=CH ₂; -C (=CH ₂) CH ₂CH ₂CH ₃; -C (CH ₃) =CHCH ₂CH ₃; -CH (CH ₃) CH=CHCH _; -CH (CH ₃) CH ₂CH=CH ₂; -CH ₂CH=C (CH ₃) ₂; 1-cyclopent-1-enyl; 1-cyclopent-2-enyl; 1-cyclopent-3-enyl; 1-cyclohex-1-enyl; 1-cyclohex-2-enyl; and, 1-cyclohexyl-3-enyl.

As used herein, "alkylaryl" refers to alkyl-substituted aryl groups and "substituted alkylaryl" refers to alkylaryl groups further bearing one or more substituents as set forth above.

The term "hetero" as used herein refers to groups or moieties containing one or more heteroatoms, such as N, O, Si and S. Thus, for example "heterocyclic" refers to cyclic groups having, for example, N, O, Si or S as part of the ring structure. "Heteroalkyl" and "heterocycloalkyl" moieties are alkyl and cycloalkyl groups as defined hereinabove, respectively, containing N, O, Si or S as part of their structure.

As used herein, the term “catalytic amount” means a sub-stoichiometric amount of catalyst relative to a reactant, except where expressly stated otherwise.

The term “photo-curable composition” as used herein refers to a composition including a component which can be cross-linked, polymerized or cured by electromagnetic wave irradiation. The term “electromagnetic wave” is a generic term including microwaves, infrared radiation, UV light, visible light, X-rays, y-rays and particles beams including α-particles, proton beams, neutron beams and electron beams.

The term "photoinitiator" as used herein denotes a compound which can be activated by an energy-carrying activation beam -such as electromagnetic radiation -for instance upon irradiation therewith. The term is intended to encompass both photoacid generators and photobase generators. Specifically, the term “photoacid generator" refers to a compound or polymer which generates an acid for the catalysis of the acid hardening resin system upon exposure to actinic radiation. The term "photobase generator" means any material which when exposed to suitable radiation generates one or more bases.

The term “Lewis acid” used herein denotes any molecule or ion -often referred to as an electrophile -capable of combining with another molecule or ion by forming a covalent bond with two electrons from the second molecule or ion: a Lewis acid is thus an electron acceptor.

As employed herein a “primary amino group” refers to an NH ₂ group that is attached to an organic radical, and a “secondary amino group” refers to an NH group that is attached to two organic radicals, which may also together be part of a ring. Where used, the term “amine hydrogen” refers to the hydrogen atoms of primary and secondary amino groups.

The “amine equivalent weight” is a calculated value determined from the amine number. That amine number is determined by titration of the amine acetate ion by a dilute, typically 1N HCl solution. For a pure material, the amine number can be calculated using the molecular weights of the pure compound and KOH (56.1 g/mol) . Instructive guidance may be found, for illustration, in https: //dowac. custhelp. com/app/answers/detail/a_id/12987.

The term “Mannich Base” is used herein in accordance with its standard definition in the art as a ketonic amine obtainable from the condensation of a ketone with formaldehyde and ammonia or a primary or secondary amine ( https: //pubchem. ncbi. nlm. nih. gov/compound/9567537#section=Top) .

“Two-component (2K) compositions” in the context of the present invention are understood to be compositions in which an epoxide-group containing component and the hardener (curative) component must be stored in separate vessels because of their (high) reactivity. The two components are mixed only shortly before application and then react –where necessary with additional activation -with bond formation and thereby formation of a polymeric network. However, catalysts may also be employed or higher temperatures applied in order to accelerate the cross-linking reaction.

As used herein the qualification “rigid” defines a component that is self-supporting, inflexible and non-compressible. Having regard to the “supporting media” mentioned above, that media should be rigid and thus should be self-supporting and provide mechanical support to the coating layer disposed thereon. Without intention to the limit the present invention, that rigid supporting media should preferably be characterized by at least one of: a tensile modulus of at least 2000 MPa, as measured in accordance with ASTM D 638 at a temperature of 23℃ ± 2℃; and, a Flexural Modulus of at least 2000 MPa, as measured in accordance with ASTM D 790 at a temperature of 23℃ ± 2℃.

The Shore A hardness of a given material mentioned herein is determined using a durometer in accordance with ISO 868 entitled “Plastics and Ebonite-Determination of Indentation Hardness by Means of a Durometer (Shore Hardness) ” , the contents of which standard are incorporated herein by reference in their entirety. Throughout the present description, all standard Shore A hardness measurements were performed on injection molded plates at 10 seconds using Type A durometer.

Viscosities of the compositions described herein are, unless otherwise stipulated, measured using the Brookfield Viscometer, Model RVT at standard conditions of 20℃ and 50%Relative Humidity (RH) . The viscometer is calibrated using silicone oils of known viscosities, which vary from 1,000 cps to 50,000 cps. A set of RV spindles that attach to the viscometer are used for the calibration. Measurements of the compositions are done using the No. 6 spindle at a speed of 20 revolutions per minute for 1 minute until the viscometer equilibrates. The viscosity corresponding to the equilibrium reading is then calculated using the calibration.

The molecular weights referred to in this specification can be measured with gel permeation chromatography (GPC) using polystyrene calibration standards, such as is done according to ASTM 3536. The residual unsaturation of the polymers mentioned herein is determined by iodine monochloride titration.

As used herein, “ambient conditions” means the temperature and pressure of the surroundings in which the coating layer or the substrate of said coating layer is located.

As used herein, "anhydrous" means the relevant composition includes less than 0.25%by weight of water. For example the composition may contain less than 0.1%by weight of water or be completely free of water. The term “essentially free of solvent” should be interpreted analogously as meaning the relevant composition comprises less than 0.25%by weight of solvent.

DETAILED DESCRIPTION OF THE INVENTION

A) EPOXIDIZED POLYOLEFIN

The composition of the present invention comprises at least one epoxidized polyolefin which is characterized by a residual olefinic unsaturation of from 0.01 to 0.5 meq/g polymer and which is selected from the group consisting of epoxidized alicyclic polyolefin and epoxidized aliphatic polyolefin. Said epoxidized polyolefin should constitute from 5 to 90 wt. %, preferably from 10 to 80 wt. %of the composition.

Whilst no theoretical lower or upper limit is imposed upon the chain length of the epoxidized polyolefin (a) , certain practical considerations should be acknowledged which impose a limit on the degree of epoxidation of the polyolefin. In particular, that degree of epoxidation of the polyolefin must be considered in relation to the effectiveness of the curative and to the properties desired in the resulting cross-linked product: a highly epoxidized olefin polymer will produce a crosslinked product of somewhat different properties than would be obtained by the use of a polymer of a lower degree of epoxidation.

With this in mind, the choice of the epoxidized polymer is obviously important and a preference should be noted for: epoxidized polyolefins which are further characterized by: an epoxy oxygen content of from 5 to 10 percent by weight; an epoxy equivalent weight of 100 to 2,000 g/eq., for example from 100 to 500 g/eq.; and, a hydroxyl group content of from 1 to 3 percent by weight. Desirably, the epoxidized polyolefins should further be characterized by a substantially linear structure and /or a number average molecular weight (Mn) of from 1000 to 10000 g/mol, for example from 1000 to 5000 g/mol.

Preferred polymers are those of butadiene, isoprene or piperylene and the copolymers of butadiene, isoprene or piperylene with: mono-olefins, such as butene, styrene and substituted styrene; nitriles, such as acrylonitrile and methacrylonitrile; or, esters of acrylic and methacrylic acid.

The epoxidized polyolefin is preferably an epoxidized polybutadiene, epoxidized polyisoprene, or an epoxidized copolymer of butadiene or isoprene with styrene. Epoxidized butadiene polymers are preferred and US Patent No. 3,030, 336 may be noted as an instructive reference for the preparation of such polymers.

In an exemplary but not-limiting embodiment, the composition is characterized by comprising from 10 to 50 wt. %of (a) an epoxidized polyolefin selected from the group consisting of epoxidized polybutadiene, epoxidized polyisoprene and epoxidized copolymers of butadiene or isoprene with styrene, said epoxidized polyolefin being further characterized by: an epoxy oxygen content of from 5 to 10 wt. %; an epoxy equivalent weight of from 100 to 500 g/eq; a hydroxyl group content of from 1 to 3 percent by weight; and, a number average molecular weight (Mn) of from 1000 to 5000 g/mol.

B) EPOXIDE COMPOUNDS

The present compositions may optionally comprise at least one epoxide compound which is distinct from the epoxidized polyolefin (a) mentioned herein above. Said epoxide compounds should not have any residual ethylenic unsaturation and moreover should constitute from 0 to 80 wt. %, preferably 0 to 70 wt. %of the composition.

The epoxide compounds (b) as used herein may include mono-functional epoxy resins, multi-or poly-functional epoxy resins, and combinations thereof. The epoxy resins may be pure compounds but equally may be mixtures of epoxy functional compounds, including mixtures of compounds having different numbers of epoxy groups per molecule. An epoxy resin may be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic and may be substituted. Further, the epoxy resin may also be monomeric or polymeric.

Without intention to limit the present invention, illustrative monoepoxide compounds include: alkylene oxides; epoxy-substituted cycloaliphatic hydrocarbons, such as cyclohexene oxide, vinylcyclohexene monoxide, (+) -cis-limonene oxide, (+) -cis, trans-limonene oxide, (-) -cis, trans-limonene oxide, cyclooctene oxide, cyclododecene oxide and α-pinene oxide; epoxy-substituted aromatic hydrocarbons; monoepoxy substituted alkyl ethers of monohydric alcohols or phenols, such as the glycidyl ethers of aliphatic, cycloaliphatic and aromatic alcohols; monoepoxy-substituted alkyl esters of monocarboxylic acids, such as glycidyl esters of aliphatic, cycloaliphatic and aromatic monocarboxylic acids; monoepoxy-substituted alkyl esters of polycarboxylic acids wherein the other carboxy group (s) are esterified with alkanols; alkyl and alkenyl esters of epoxy-substituted monocarboxylic acids; epoxyalkyl ethers of polyhydric alcohols wherein the other OH group (s) are esterified or etherified with carboxylic acids or alcohols; and, monoesters of polyhydric alcohols and epoxy monocarboxylic acids, wherein the other OH group (s) are esterified or etherified with carboxylic acids or alcohols.

By way of example, the following glycidyl ethers might be mentioned as being particularly suitable monoepoxide compounds for use herein: methyl glycidyl ether; ethyl glycidyl ether; propyl glycidyl ether; butyl glycidyl ether; pentyl glycidyl ether; hexyl glycidyl ether; cyclohexyl glycidyl ether; octyl glycidyl ether; 2-ethylhexyl glycidyl ether; allyl glycidyl ether; benzyl glycidyl ether; phenyl glycidyl ether; 4-tert-butylphenyl glycidyl ether; 1-naphthyl glycidyl ether; 2-naphthyl glycidyl ether; 2-chlorophenyl glycidyl ether; 4-chlorophenyl glycidyl ether; 4-bromophenyl glycidyl ether; 2, 4, 6-trichlorophenyl glycidyl ether; 2, 4, 6-tribromophenyl glycidyl ether; pentafluorophenyl glycidyl ether; o-cresyl glycidyl ether; m-cresyl glycidyl ether; and, p-cresyl glycidyl ether.

In an important embodiment, the monoepoxide compound conforms to Formula (I) herein below:

wherein: R ², R ³, R ⁴ and R ⁵ may be the same or different and are independently selected from hydrogen, a halogen atom, a C ₁-C ₈ alkyl group, a C ₃ to C ₁₀ cycloalkyl group, a C ₂-C ₁₂ alkenyl, a C ₆-C ₁₈ aryl group or a C ₇-C ₁₈ aralkyl group, with the proviso that at least one of R ³ and R ⁴ is not hydrogen.

It is preferred that R ², R ³ and R ⁵ are hydrogen and R ⁴ is either a phenyl group or a C ₁-C ₈ alkyl group and, more preferably, a C ₁-C ₄ alkyl group.

Having regard to this embodiment, exemplary monoepoxides include: ethylene oxide; 1, 2-propylene oxide (propylene oxide) ; 1, 2-butylene oxide; cis-2, 3-epoxybutane; trans-2, 3-epoxybutane; 1, 2-epoxypentane; 1, 2-epoxyhexane; 1, 2-heptylene oxide; decene oxide; butadiene oxide; isoprene oxide; and, styrene oxide.

In certain embodiments of the present invention, an election is made to use in part (b) of the composition at least one monoepoxide compound selected from the group consisting of: ethylene oxide; propylene oxide; cyclohexene oxide; (+) -cis-limonene oxide; (+) -cis, trans-limonene oxide; (-) -cis, trans-limonene oxide; cyclooctene oxide; and, cyclododecene oxide. It is particularly preferred if propylene oxide is used as the reactant monoepoxide compound: this statement of particular preference is intended to encompass said propylene oxide being either one of the epoxide compounds present in part (b) or the sole epoxide compound present.

Again, without intention to limit the present invention, suitable polyepoxide compounds for part (b) of the composition may be liquid or solid under ambient conditions and should have an epoxy equivalent weight of from 100 to 700 g/eq, for example from 120 to 320 g/eq. And generally, diepoxide compounds having epoxy equivalent weights of less than 500 or even less than 400 are preferred: this is predominantly from a costs standpoint, as in their production, lower molecular weight epoxy resins require more limited processing in purification.

As examples of types or groups of polyepoxide compounds which may be used in part (b) , mention may be made of: glycidyl ethers of polyhydric alcohols and polyhydric phenols; glycidyl esters of polycarboxylic acids; and, epoxidized polyethylenically unsaturated esters, ethers and amides.

Suitable diglycidyl ether compounds may be aromatic, aliphatic or cycloaliphatic in nature and, as such, can be derivable from dihydric phenols and dihydric alcohols. And useful classes of such diglycidyl ethers are: diglycidyl ethers of aliphatic and cycloaliphatic diols, such as 1, 2-ethanediol, 1, 4-butanediol, 1, 6-hexanediol, 1, 8-octanediol, 1, 12–dodecanediol, cyclopentane diol and cyclohexane diol; bisphenol A based diglycidylethers; bisphenol F diglycidyl ethers; diglycidyl o-phthalate, diglycidyl isophthalate and diglycidyl terephthalate; polyalkyleneglycol based diglycidyl ethers, in particular polypropyleneglycol diglycidyl ethers; and, polycarbonatediol based glycidyl ethers. Other suitable diepoxides which might also be mentioned include: diepoxides of double unsaturated fatty acid C1-C18 alkyl esters; butadiene diepoxide; polybutadiene diglycidyl ether; vinylcyclohexene diepoxide; and, limonene diepoxide.

Further illustrative polyepoxide compounds include but are not limited to: glycerol polyglycidyl ether; trimethylolpropane polyglycidyl ether; pentaerythritol polyglycidyl ether; diglycerol polyglycidyl ether; polyglycerol polyglycidyl ether; and, sorbitol polyglycidyl ether.

And examples of highly preferred polyepoxide compounds include: bisphenol-A epoxy resins, such as DER ^TM 331, and DER ^TM 383; bisphenol-F epoxy resins, such as DER ^TM 354; bisphenol-A/F epoxy resin blends, such as DER ^TM 353; aliphatic glycidyl ethers, such as DER ^TM 736; polypropylene glycol diglycidyl ethers, such as DER ^TM 732; solid bisphenol-A epoxy resins, such as DER ^TM 661 and DER ^TM 664 UE; solutions of bisphenol-A solid epoxy resins, such as DER ^TM 671-X75; epoxy novolac resins, such as DEN ^TM 438; brominated epoxy resins such as DER ^TM 542; castor oil triglycidyl ether, such as ERISYS ^TM GE-35H; polyglycerol-3-polyglycidyl ether, such as ERISYS ^TM GE-38; and, sorbitol glycidyl ether, such as ERISYS ^TM GE-60.

In an exemplary but non-limiting embodiment of the present invention, the composition is characterized by comprising from 20 to 70 wt. %of (b) at least one polyepoxide compound selected from the group consisting of: glycidyl ethers of polyhydric alcohols; gycidyl ethers of polyhydric phenols; and, glycidyl esters of polycarboxylic acids.

Whilst it is does not represent a preferred embodiment, the present invention does not preclude the curable compositions further comprising one or more cyclic compounds selected from the group consisting of: oxetanes; cyclic carbonates; cyclic anhydrides; and, lactones. The disclosures of the following citations may be instructive in disclosing suitable cyclic carbonate functional compounds: US Patent No. 3,535,342; US Patent No. 4,835,289; US Patent No. 4,892,954; UK Patent No. GB-A-1,485,925; and, EP-A-0 119 840. However, such cyclic compounds should constitute less than 20 wt. %, preferably less than 10 wt. %or less than 5 wt. %, based on the total weight of parts (a) and (b) of the composition.

C) THIOL COMPOUND (S)

The composition of the present invention comprises at least one compound which has at least two reactive mercapto-groups per molecule. Suitable mercapto-group containing compounds, which may be used alone or in combination, include but are not limited to the following.

· Liquid mercaptan-terminated polysulfide polymers of which commercial examples include:

polymers (available from Morton Thiokol) , in particular the types LP-3, LP-33, LP-980, LP-23, LP-55, LP-56, LP-12, LP-31, LP-32 and LP-2 thereof; and,

polymers (from Akzo Nobel) , in particular the types G10, G112, G131, G1, G12, G21, G22, G44 and G 4.

· Mercaptan-terminated polyoxyalkylene ethers, obtainable by reacting polyoxyalkylenedi-and -triols either with epichlorohydrin or with an alkylene oxide, followed by sodium hydrogen sulfide.

· Mercaptan-terminated compounds in the form of polyoxyalkylene derivatives, known under the trade name of

(from Cognis) , in particular the types WR-8, LOF and 3-800 thereof.

· Polyesters of thiocarboxylic acids of which particular examples include: pentaerythritol tetramercapto-acetate (PETMP) ; trimethylolpropane trimercaptoacetate (TMPMP) ; glycol dimercaptoacetate; and, the esterification products of polyoxyalkylene diols and triols, ethoxylated trimethylolpropane and polyester diols with thiocarboxylic acids such as thioglycolic acid and 2-or 3-mercaptopropionic acid.

· 2, 4, 6-trimercapto-1, 3, 5-triazine, 2, 2′- (ethylenedioxy) -diethanethiol (triethylene glycol dimercaptan) and /or ethanedithiol.

A preference for the use of polyesters of thiocarboxylic acids and, in particular, for the use of at least one of pentaerythritol tetramercapto-acetate (PETMP) , trimethylolpropane trimercaptoacetate (TMPMP) and glycol dimercaptoacetate is acknowledged.

The at least one mercapto-group containing compound should constitute from 1 to 40 wt. %, preferably from 3 to 30 wt. %of the composition. And in a preferred embodiment, the composition of the present invention is characterized by comprising from 5 to 20 wt. %of (c) polyester of a thiocarboxylic acid selected from the group consisting of pentaerythritol tetramercapto-acetate (PETMP) , trimethylolpropane trimercaptoacetate (TMPMP) , glycol dimercaptoacetate and mixtures thereof.

D) PHOTOINITIATOR

The compositions of the present invention include d) at least one free radical photoinitiator compound which initiates the polymerization or hardening of the compositions upon irradiation with actinic radiation. It is established that photo-polymerizable compositions of the present invention could be both cationically polymerizable or free-radically polymerizable: whilst epoxy groups are cationically active, the inventors have elected a free-radical polymerization mechanism based on the presence in the composition of free-radically active, unsaturated groups.

Typically, free radical photoinitiators are divided into those that form radicals by cleavage, known as "Norrish Type I" , and those that form radicals by hydrogen abstraction, known as "Norrish Type II" . The Norrish Type II photoinitiators require a hydrogen donor, which serves as the free radical source: as the initiation is based on a bimolecular reaction, the Norrrish Type II photoinitiators are generally slower than Norrish Type I photoinitiators which are based on the unimolecular formation of radicals. On the other hand, Norrish Type II photoinitiators possess better optical absorption properties in the near-UV spectroscopic region. Whilst active hydrogen species are indeed present in the compositions according to the present invention, the skilled artisan should be able to select an appropriate free radical photoinitiator for additive fabrication based on the actinic radiation being employed in curing and the sensitivity of the photoinitiator (s) at that wavelength.

In accordance with an embodiment of the invention, the composition comprises d) at least one free radical photoinitiator selected from the group consisting of: benzoylphosphine oxides; aryl ketones; benzophenones; hydroxylated ketones; 1-hydroxyphenyl ketones; ketals; metallocenes; and combinations thereof.

In accordance with a preferred embodiment of the invention, the composition comprises d) at least one free radical photoinitiator selected from the group consisting of: benzoin dimethyl ether; 1-hydroxycyclohexyl phenyl ketone; benzophenone; 4-chlorobenzophenone; 4-methylbenzophenone; 4-phenylbenzophenone; 4, 4'-bis (diethylamino) benzophenone; 4, 4'-bis (N, N'-dimethylamino) benzophenone (Michler's ketone) ; isopropylthioxanthone; 2-hydroxy-2-methylpropiophenone; 2-methyl-4- (methylthio) -2-morpholinopropiophenone; methyl phenylglyoxylate; methyl 2-benzoylbenzoate; 2-ethylhexyl 4- (dimethylamino) benzoate; ethyl 4- (N, N-dimethylamino) benzoate; phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide; diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide; ethyl phenyl (2, 4, 6-trimethylbenzoyl) phosphinate; and, combinations thereof.

The photoinitiator d) should be present in the composition in an amount of from 0.05 to 5.0 wt. %, for example from 0.05 to 2.0 wt. %, based on the weight of the composition.

The purpose of irradiation of the curable compositions is to generate the active species from the photoinitiator d) which initiates the cure reactions. Once that species is generated, the cure chemistry is subject to the same rules of thermodynamics as any chemical reaction: the reaction rate may be accelerated by heat. The practice of using thermal treatments to enhance the actinic-radiation cure of monomers is generally known in the art, with an illustrative instructive reference being Crivello et al., “Dual Photo-and thermally initiated cationic polymerization of epoxy monomers, ” Journal of Polymer Science A, Polymer Chemistry., Vol. 44, Issue: 23, pp. 6750-6764, (Dec. 1, 2006) .

The use of the photoinitiator d) -and also the photobase generator and photoacid generators mentioned herein below -may produce residue compounds from the photochemical reaction in the final cured product. The residues may be detected by conventional analytical techniques such as: infrared, ultraviolet and NMR spectroscopy; gas or liquid chromatography; and, mass spectroscopy. Thus, the present invention may comprise cured (epoxy) matrix copolymers and detectable amounts of residues from a free radical photo-initiator and a photo-base/acid generator. Such residues are present in small amounts and do not normally interfere with the desired physiochemical properties of the final cured product.

As would be recognized by the skilled artisan, photosensitizers can be incorporated into the compositions to improve the efficiency with which the photoinitiator d) uses the energy delivered. The term "photosensitizer" is used in accordance with its standard meaning to represent any substance that either increases the rate of photoinitiated polymerization or shifts the wavelength at which polymerization occurs: Odian, Principles of Polymerization 3rd Edition (1991) , Page 222 provides an instructive reference in this regard. When present, photosensitizers should be used in an amount of from 5 to 25 wt. %, based on the weight of the photoinitiator d) .

E) POLYAMINE EPOXY CURING AGENT:

The present composition further comprises at least one polyamine having at least two amine hydrogens reactive toward epoxide groups. In particular, said polyamine may contain primary and /or secondary amine groups and have an equivalent weight per primary or secondary amine group of not more than 150, preferably not more than 125.

Suitable polyamines for use in the present invention, which may be used alone or in combination, include but are not limited to the following.

i) Aliphatic, cycloaliphatic or arylaliphatic primary diamines of which the following examples may be mentioned: 2, 2-dimethyl-1, 3-propanediamine; 1, 3-pentanediamine (DAMP) ; 1, 5-pentanediamine; 1, 5-diamino-2-methylpentane (MPMD) ; 2-butyl-2-ethyl-1, 5-pentanediamine (C11-neodiamine) ; 1, 6-hexanediamine (hexamethylenediamine, HMDA) ; 2, 5-dimethyl-1, 6-hexanediamine; 2, 2, 4-and /or 2, 4, 4-trimethylhexamethylenediamine; 1, 7-heptanediamine; 1, 8-octanediamine; 1, 9-nonanediamine; 1, 10-decanediamine; 1, 11-undecanediamine; 1, 12-dodecanediamine; 1, 2-, 1, 3-and 1, 4-diaminocyclohexane; bis (4-aminocyclohexyl) methane; bis (4-amino-3-methylcyclohexyl) methane; bis (4-amino-3-ethylcyclohexyl) methane; bis (4-amino-3, 5-dimethylcyclohexyl) methane; bis (4-amino-3-ethyl-5-methylcyclohexyl) methane; 1-amino-3-aminomethyl-3, 5, 5-trimethylcyclohexane (isophorone diamine, IPDA) ; 2-and /or 4-methyl-1, 3-diaminocyclohexane; 1, 3-bis (aminomethyl) -cyclohexane; 1, 4-bis (aminomethyl) cyclohexane; 2, 5 (2, 6) -bis (aminomethyl) -bicyclo [2.2.1] heptane (norborane diamine, NBDA) ; 3 (4) , 8 (9) -bis (aminomethyl) tricyclo [5.2.1.0 ^2, 6] -decane (TCD-diamine) ; 1, 4-diamino-2, 2, 6-trimethylcyclohexane (TMCDA) ; 1, 8-menthanediamine; 3, 9-bis (3-aminopropyl) -2, 4, 8, 10-tetraoxaspiro [5.5] undecane; and, 1, 3-bis (aminomethyl) benzene (MXDA) .

ii) Tertiary amine group-containing polyamines with two or three primary aliphatic amine groups of which the following specific examples may be mentioned: N, N′-bis (aminopropyl) -piperazine; N, N-bis (3-aminopropyl) methylamine; N, N-bis (3-aminopropyl) ethylamine; N, N-bis (3-aminopropyl) propylamine; N, N-bis (3-aminopropyl) cyclohexylamine; N, N-bis (3-aminopropyl) -2-ethyl-hexylamine; tris (2-aminoethyl) amine; tris (2-aminopropyl) amine; tris (3-aminopropyl) amine; and, the products from the double cyanoethylation and subsequent reduction of fatty amines derived from natural fatty acids, such as N, N-bis (3-aminopropyl) dodecylamine and N, N-bis (3-aminopropyl) tallow alkylamine, commercially available as

Y12D and

YT (from Akzo Nobel) .

iii) Ether group-containing aliphatic primary polyamines of which the following specific examples may be mentioned: bis (2-aminoethyl) ether; 3, 6-dioxaoctane-1, 8-diamine; 4, 7-dioxadecane-1, 10-diamine; 4, 7-dioxadecane-2, 9-diamine; 4, 9-dioxadodecane-1, 12-diamine; 5, 8-dioxadodecane-3, 10-diamine; 4, 7, 10-trioxatridecane-1, 13-diamine and higher oligomers of these diamines; bis (3-aminopropyl) polytetrahydrofuranes and other polytetrahydrofuran diamines; cycloaliphatic ether group-containing diamines obtained from the propoxylation and subsequent amination of 1, 4-dimethylolcyclohexane, such as that material commercially available as

RFD-270 (from Huntsman) ; polyoxyalkylenedi-or –triamines obtainable as products from the amination of polyoxyalkylenedi-and -triols and which are commercially available under the name of

(from Huntsman) , under the name of polyetheramine (from BASF) or under the name of PC

(from Nitroil) . A particular preference may be noted for the use of

D-230,

D-400,

D-600,

D-2000,

D-4000,

T-403,

T-3000,

T-5000,

EDR-104,

EDR-148 and

EDR-176, as well as corresponding amines from BASF or Nitroil.

iv) Primary diamines with secondary amine groups of which the following examples may be mentioned: 3- (2-aminoethyl) aminopropylamine, bis (hexamethylene) triamine (BHMT) ; diethylenetriamine (DETA) ; triethylenetetramine (TETA) ; tetraethylenepentamine (TEPA) ; pentaethylenehexamine (PEHA) ; higher homologs of linear polyethyleneamines, such as polyethylene polyamines with 5 to 7 ethyleneamine units (so-called “higher ethylenepolyamine, ” HEPA) ; products from the multiple cyanoethylation or cyanobutylation and subsequent hydrogenation of primary di-and polyamines with at least two primary amine groups, such as dipropylenetriamine (DPTA) , N- (2-aminoethyl) -1, 3-propanediamine (N3-amine) , N, N′-bis (3-aminopropyl) ethylenediamine (N4-amine) , N, N′-bis (3-aminopropyl) -1, 4-diaminobutane, N5- (3-aminopropyl) -2-methyl-1, 5-pentanediamine, N3- (3-aminopentyl) -1, 3-pentanediamine, N5- (3-amino-1-ethylpropyl) -2-methyl-1, 5-pentanediamine or N, N′-bis (3-amino-1-ethylpropyl) -2-methyl-1, 5-pentanediamine.

v) Polyamines with one primary and at least one secondary amino group of which the following examples may be mentioned: N-butyl-1, 2-ethanediamine; N-hexyl-1, 2-ethanediamine; N- (2-ethylhexyl) -1, 2-ethanediamine; N- cyclohexyl-1, 2-ethanediamine; 4-aminomethyl-piperidine; N- (2-aminoethyl) piperazine; N-methyl-1, 3-propanediamine; N-butyl-1, 3-propanediamine; N- (2-ethylhexyl) -1, 3-propanediamine; N-cyclohexyl-1, 3-propanediamine; 3-methylamino-1-pentylamine; 3-ethylamino-1-pentylamine; 3-cyclohexylamino-1-pentylamine; fatty diamines such as N-cocoalkyl-1, 3-propanediamine; products from the Michael-type addition reaction of primary aliphatic diamines with acrylonitrile, maleic or fumaric acid diesters, citraconic acid diesters, acrylic and methacrylic acid esters, acrylic and methacrylic acid amides and itaconic acid diesters, reacted in a 1: 1 molar ratio; products from the partial reductive alkylation of primary polyamines with aldehydes or ketones, especially N-monoalkylation products of the previously mentioned polyamines with two primary amine groups and in particular of 1, 6-hexanediamine, 1, 5-diamino-2-methylpentane, 1, 3-bis (aminomethyl) cyclohexane, 1, 4-bis (aminomethyl) cyclohexane, 1, 3-bis (aminomethyl) benzene, BHMT, DETA, TETA, TEPA, DPTA, N3-amine and N4-amine, wherein preferred alkyl groups are benzyl, isobutyl, hexyl and 2-ethylhexyl; and, partially styrenated polyamines such as those commercially available as

240 (from Mitsubishi Gas Chemical) .

vi) Secondary diamines and, in particular, N, N′-dialkylation products of the previously mentioned polyamines with two primary amine groups, especially N, N′-dialkylation products of 1, 6-hexanediamine, 1, 5-diamino-2-methylpentane, 1, 3-bis (aminomethyl) cyclohexane, 1, 4-bis (aminomethyl) -cyclohexane, 1, 3-bis (aminomethyl) benzene, BHMT, DETA, TETA, TEPA, DPTA, N3-amine or N4-amine, wherein preferred alkyl groups are 2-phenylethyl, benzyl, isobutyl, hexyl and 2-ethylhexyl.

vii) Aromatic polyamines of which mention may be made of: m-and p-phenylenediamine; 4, 4′-, 2, 4′and 2, 2′-diaminodiphenylmethane; 3, 3′-dichloro-4, 4′-diaminodiphenylmethane (MOCA) ; 2, 4-and 2, 6-tolylenediamine; mixtures of 3, 5-dimethylthio-2, 4-and -2, 6-tolylenediamine (available as

300 from Albermarle) ; mixtures of 3, 5-diethyl-2, 4-and -2, 6-tolylene diamine (DETDA) ; 3, 3′, 5, 5′-tetraethyl-4, 4′-diaminodiphenylmethane (M-DEA) ; 3, 3′, 5, 5′-tetraethyl-2, 2′-dichloro-4, 4′-diaminodiphenylmethane (M-CDEA) ; 3, 3′-diisopropyl-5, 5′-dimethyl-4, 4′-diaminodiphenylmethane (M-MIPA) ; 3, 3′, 5, 5′-tetraisopropyl-4, 4′-diaminodiphenylmethane (M-DIPA) ; 4, 4′-diamino diphenyl-sulfone (DDS) ; 4-amino-N- (4-aminophenyl) benzenesulfonamide; 5, 5′-methylenedianthranilic acid; dimethyl- (5, 5′-methylenedianthranilate) ; 1, 3-propylene-bis (4-aminobenzoate) ; 1, 4-butylene-bis (4-aminobenzoate) ; polytetramethylene oxide-bis (4-aminobenzoate) (available as

from Air Products) ; 1, 2-bis (2-aminophenylthio) ethane, 2-methylpropyl- (4-chloro-3, 5-diaminobenzoate) ; and, tert. butyl- (4-chloro-3, 5-diaminobenzoate) .

viii) Polyamidoamines of which indicative members include the reaction products of monohydric or polyhydric carboxylic acids or the esters or anhydrides thereof, -in particular dimer fatty acids -and an aliphatic, cycloaliphatic or aromatic polyamine, for instance polyalkyleneamines such as DETA or TETA. Commercially available polyamidoamines include:

100, 125, 140 and 150 (from Cognis) ;

223, 250 and 848 (from Huntsman) ;

3607 and 530 (from Huntsman) ; and,

EH 651, EH 654, EH 655, EH 661 and EH 663 (from Cytec) .

ix) Mannich bases and in particular the commercially available phenalkamines

NC-541, NC-557, NC-558, NC-566, Lite 2001 and Lite 2002 (available from Cardolite) ,

3440, 3441, 3442 and 3460 (available from Huntsman) and

EH 614, EH 621, EH 624, EH 628 and EH 629 (available from Cytec) .

Preferred among the aforementioned polyamines having at least two primary aliphatic amine groups are: isophorone diamine (IPDA) ; hexamethylene diamine (HMDA) ; 1, 3-bis (amino-methyl) cyclohexane; 1, 4-bis (aminomethyl) cyclohexane; bis (4-amino-cyclohexyl) methane; bis (4-amino-3-methylcyclohexyl) methane; NBDA; and, ether group-containing polyamines with an average molecular weight of up to 500 g/mol. Particularly preferred among said ether group-containing polyamines are

D-230 and D-600 (available from Huntsman) .

In an important embodiment of the present invention, the composition comprises a cycloaliphatic di-, tri-or higher polyamine. Desirably, said cycloaliphatic are primary amines and contain at least one primary amine group and more desirably the cycloaliphatic residues of the compounds contain one or more primary amine groups. Typical examples of such cycloaliphatic amines include primary amines containing one or two cyclohexyl, cycloheptyl, or cyclopentyl residues or combinations thereof. The cycloaliphatic residue is typically in α-or β-position to the amine groups, said α-position meaning directly bonded to the amino group and said β-position means the position adjacent to the α-position. And particular examples of such cycloaliphatic amine curing agents include: methylene dicyclohexylamines; methyl methylene dicyclohexylamines; dimethyl methylene dicyclohexylamines; and, isophorone diamines. Suitable cycloaliphatic amine curing agents are commercially available under the trade designation

2264,

2280,

2286 from Evonik; and, BAXXODUR EC331 from BASF, Ludwigshafen, Germany.

When formulating the composition, the polyamine curing agent e) is included in an amount such that the composition is in toto characterized by a molar ratio of epoxy-reactive groups to epoxy groups from 0.95: 1 to 1.5: 1, for example from 0.95: 1 to 1.1: 1. Notably, the molar ratio of epoxy-reactive groups to epoxy groups of 1: 1 is included with these stated ranges and itself represents a highly preferred molar ratio.

In an alternative expression of the preferred amount of polyamine curing agent, which expression is not intended to be mutually exclusive of that given above, the composition may be characterized by comprising from 1 to 50 wt. %, preferably from 15 to 40 wt. %of e) said polyamine curing agent.

F) ADDITIVES AND ADJUNCT INGREDIENTS

Said compositions obtained in the present invention –which can be formulated as either one component (1K) or two component compositions -will typically further comprise adjuvants and additives that can impart improved properties to these compositions. For instance, the adjuvants and additives may impart one or more of: improved elastic properties; improved elastic recovery; longer enabled processing time; faster curing time; and, lower residual tack.

Included among such adjuvants and additives –which independently of one another may be included in single components or both components of a two (2K) component composition -are catalysts, plasticizers, stabilizers including UV stabilizers, antioxidants, tougheners, fillers, reactive diluents, drying agents, adhesion promoters, fungicides, flame retardants, rheological adjuvants, color pigments or color pastes, and/or optionally also, to a small extent, non-reactive diluents.

For completeness, it is noted that in general adjunct materials and additives which contain epoxide-reactive groups will be blended into the hardener (curative) component of a two (2K) component composition. Materials that contain epoxide groups or which are reactive with the hardener (s) are generally formulated into the epoxide-containing component of a two (2K) component composition. Unreactive materials may be formulated into either or both of the components.

Suitable catalysts are substances that promote the reaction between the epoxide groups and the epoxide-reactive groups, for instance the reaction between the amine groups and the epoxide groups. A specific example relates to the use of an amine catalyst which functions by de-protonation of reactive thiol (-SH) groups present to thiolate (-S") , which thiolate reacts with epoxy groups by nucleophilic ring opening polymerization.

Without intention to the limit the catalysts used in the present invention, mention may be made of the following suitable catalysts: i) acids or compounds hydrolyzable to acids, in particular a) organic carboxylic acids, such as acetic acid, benzoic acid, salicylic acid, 2-nitrobenzoic acid and lactic acid; b) organic sulfonic acids, such as methanesulfonic acid, p-toluenesulfonic acid and 4-dodecylbenzenesulfonic acid; c) sulfonic acid esters; d) inorganic acids, such as phosphoric acid; e) Lewis acid compounds, such as BF ₃ amine complexes, SbF ₆ sulfonium compounds, bis-arene iron complexes; f) Bronsted acid compounds, such as pentafluoroantimonic acid complexes; and, e) mixtures of the aforementioned acids and acid esters; ii) tertiary amines, such as 1, 4-diazabicyclo [2.2.2] octane, benzyldimethylamine, α-methylbenzyl dimethylamine, triethanolamine, dimethylamino propylamine, imidazoles -including N-methylimidazole, N-vinylimidazole and 1, 2-dimethylimidazole -and salts of such tertiary amines; iii) quaternary ammonium salts, such as benzyltrimethyl ammonium chloride; iv) amidines, such as 1, 8-diazabicyclo [5.4.0] undec-7-ene; v) guanidines, such as 1, 1, 3, 3-tetramethylguanidine; vi) phenols, in particular bisphenols; vii) phenol resins; viii) Mannich bases; and, ix) phosphites, such as di-and triphenylphosphites.

In an embodiment, an amine catalyst for the curing a composition based on the epoxy resin may be photobase generator: upon exposure to UV radiation –typically in the wavelength from 320 to 420 nm -said photobase generator releases an amine, which catalyzes the addition of the epoxide reactive groups to the epoxide. The photobase generator is not specifically limited so long as it generates an amine directly or indirectly with light irradiation. However, suitable photobase generators which may be mentioned include: benzyl carbamates; benzoin carbamates; o-carbamoylhydroxyamines; O-carbamoyloximes; aromatic sulfonamides; alpha-lactams; N- (2-allylethenyl) amides; arylazide compounds, N-arylformamides, and 4- (ortho-nitrophenyl) dihydropyridines.

For completeness, the preparation of photobase generator compounds is known in the art and instructive references include: J. Cameron et al., J. Am. Chem. Soc, Vol. 113, No. 11, 4303-4313 (1991) ; J. Cameron et al., J. Polym. Mater. Sci. Eng., 64, 55 (1991) ; J. Cameron, et al., J. Org. Chem., 55, 5919-5922 (1990) ; and, U.S. 5,650,261 (Winkel) . Moreover, photobase generators are further described in: M. Shirai et al. Photochemical Reactions of Quatenary Ammonium Dithiocarbamates as Photobase Generators and Their Use in The Photoinitiated Thermal Crosslinking of Poly (gycidylmethacrylate) , Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 39, pp. 1329-1341 (2001) ; and, M. Shirai et al., Photoacid and photobase generators: chemistry and applications to polymeric materials, Progress in Polymer Science, Vol. 21, pp. 1-45, XP-002299394, 1996.

In an alternative embodiment, an acid catalyst may be selected from photoacid generators (PAGs) : upon irradiation with light energy, ionic photoacid generators undergo a fragmentation reaction and release one or more molecules of Lewis or Bronsted acid that catalyze the ring opening and addition of the pendent epoxide groups to form a crosslink. Useful photoacid generators are thermally stable, do not undergo thermally induced reactions with the forming copolymer and are readily dissolved or dispersed in the curable compositions. Photoacid generators are known in the art and instructive reference may be made to: K. Dietliker, Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints, Vol. Ill, SITA Technology Ltd., London (1991) ; and, Kirk-Othmer Encyclopedia of Chemical Technology, 4. Sup. Th Edition, Supplement Volume, John Wiley and Sons, New York, pp 253-255.

Exemplary cations which may be used as the cationic portion of the ionic PAG of the invention include organic onium cations such as those described in US Patent No. 4,250,311, US Patent No. 3,113,708, US Patent No. 4,069,055, US Patent No. 4,216,288, US Patent No. 5,084,586, US Patent No. 5,124,417, and, US Patent No. 5,554,664. The references specifically encompass aliphatic or aromatic Group IVA and VIIA (CAS version) centered onium salts, with a preference being noted for I-, S-, P-, Se-N-and C-centered onium salts, such as those selected from sulfoxonium, iodonium, sulfonium, selenonium, pyridinium, carbonium and phosphonium.

As is known in the art, the nature of the counter-anion in the ionic photoacid generator (PAG) can influence the rate and extent of cationic addition polymerization of the epoxy groups. For illustration, Crivello et al. Chem. Mater., 4, 692, (1992) reports that the order of reactivity among commonly used nucleophilic anions is SbF ₆ > AsF ₆ > PF ₆ > BF ₄. The influence of the anion on reactivity has been ascribed to three principle factors which the skilled artisan should compensate for in the present invention: (1) the acidity of the protonic or Lewis acid generated; (2) the degree of ion-pair separation in the propagating cationic chain; and, (3) the susceptibility of the anions to fluoride abstraction and consequent chain termination.

A "plasticizer" for the purposes of this invention is a substance that decreases the viscosity of the composition and thus facilitates its processability. Herein the plasticizer may constitute up to 10 wt. %or up to 5 wt. %, based on the total weight of the composition, and is preferably selected from the group consisting of: polydimethylsiloxanes (PDMS) ; diurethanes; ethers of monofunctional, linear or branched C4-C16 alcohols, such as Cetiol OE (obtainable from Cognis Deutschland GmbH, Düsseldorf) ; esters of abietic acid, butyric acid, thiobutyric acid, acetic acid, propionic acid esters and citric acid; esters based on nitrocellulose and polyvinyl acetate; fatty acid esters; dicarboxylic acid esters; esters of OH-group-carrying or epoxidized fatty acids; glycolic acid esters; benzoic acid esters; phosphoric acid esters; sulfonic acid esters; trimellitic acid esters; epoxidized plasticizers; polyether plasticizers, such as end-capped polyethylene or polypropylene glycols; polystyrene; hydrocarbon plasticizers; chlorinated paraffin; and, mixtures thereof. It is noted that, in principle, phthalic acid esters can be used as the plasticizer but these are not preferred due to their toxicological potential. It is preferred that the plasticizer comprises or consists of one or more polydimethylsiloxane (PDMS) .

"Stabilizers" for purposes of this invention are to be understood as antioxidants, UV stabilizers or hydrolysis stabilizers. Herein stabilizers may constitute in toto up to 10 wt. %or up to 5 wt. %, based on the total weight of the composition. Standard commercial examples of stabilizers suitable for use herein include: sterically hindered phenols; thioethers; benzotriazoles; benzophenones; benzoates; cyanoacrylates; acrylates; amines of the hindered amine light stabilizer (HALS) type; phosphorus; sulfur; and, mixtures thereof.

Those compositions of the present invention may optionally contain a toughening rubber which is desirably present in the form of a rubber-modified epoxy resin, in the form of core-shell particles or a combination thereof. The toughening rubber should have a glass transition temperature (T _g) of no greater than -25℃: preferably at least a portion of the toughening rubber should have a glass transition temperature (T _g) of -40℃ or lower, more preferably -50℃ or lower and even more preferably -70℃ or lower.

As noted, the compositions according to the present invention can additionally contain fillers. Suitable here are, for example, chalk, lime powder, precipitated and/or pyrogenic silicic acid, zeolites, bentonites, magnesium carbonate, diatomite, alumina, clay, talc, titanium oxide, iron oxide, zinc oxide, sand, quartz, flint, mica, glass powder, and other ground mineral substances. Organic fillers can also be used, in particular carbon black, graphite, wood fibers, wood flour, sawdust, cellulose, cotton, pulp, cotton, wood chips, chopped straw, chaff, ground walnut shells, and other chopped fibers. Short fibers such as glass fibers, glass filament, polyacrylonitrile, carbon fibers, Kevlar fibers, or polyethylene fibers can also be added. Aluminum powder is likewise suitable as a filler.

The pyrogenic and/or precipitated silicic acids advantageously have a BET surface area from 10 to 90 m ²/g. When they are used, they do not cause any additional increase in the viscosity of the composition according to the present invention, but do contribute to strengthening the cured composition.

It is likewise conceivable to use pyrogenic and/or precipitated silicic acids having a higher BET surface area, advantageously from 100 to 250 m ²/g, in particular from 110 to 170 m ²/g, as a filler: because of the greater BET surface area, the effect of strengthening the cured composition is achieved with a smaller proportion by weight of silicic acid.

Also suitable as fillers are hollow spheres having a mineral shell or a plastic shell. These can be, for example, hollow glass spheres that are obtainable commercially under the trade names Glass

Plastic-based hollow spheres, such as

or

may be used and are described in EP 0 520 426 B1: they are made up of inorganic or organic substances and each have a diameter of 1 mm or less, preferably 500 μm or less.

Fillers which impart thixotropy to the composition may be preferred for many applications: such fillers are also described as rheological adjuvants, e.g. hydrogenated castor oil, fatty acid amides, or swellable plastics such as PVC.

The total amount of fillers present in the compositions of the present invention will preferably be from 1 to 20 wt. %, and more preferably from 1 to 10 wt. %, based on the total weight of the composition. The desired viscosity of the curable composition will typically be determinative of the total amount of filler added and it is submitted that in order to be readily extrudable out of a suitable dispensing apparatus –such as a printer –the curable compositions should possess a viscosity of from 1000 to 100000, preferably from 1000 to 80000 mPas, or even from 1000 to 50000 mPas.

Examples of suitable pigments are titanium dioxide, iron oxides, or carbon black.

In order to enhance shelf life even further, it is often advisable to further stabilize the compositions of the present invention with respect to moisture penetration through using drying agents. A need also occasionally exists to lower the viscosity of an adhesive or sealant composition according to the present invention for specific applications, by using reactive diluent (s) . When present, the total amount of reactive diluents present will typically be up to 15 wt. %, for example up to 5 wt. %, based on the total weight of the composition.

The presence of non-reactive diluents in the compositions of the present invention is also not precluded where this can usefully moderate the viscosities thereof. For instance, but for illustration only, the compositions may contain one or more of: xylene; 2-methoxyethanol; dimethoxyethanol; 2-ethoxyethanol; 2-propoxyethanol; 2-isopropoxyethanol; 2- butoxyethanol; 2-phenoxyethanol; 2-benzyloxyethanol; benzyl alcohol; ethylene glycol; ethylene glycol dimethyl ether; ethylene glycol diethyl ether; ethylene glycol dibutyl ether; ethylene glycol diphenyl ether; diethylene glycol; diethylene glycol-monomethyl ether; diethylene glycol-monoethyl ether; diethylene glycol-mono-n-butyl ether; diethylene glycol dimethyl ether; diethylene glycol diethyl ether; diethylene glycoldi-n-butylyl ether; propylene glycol butyl ether; propylene glycol phenyl ether; dipropylene glycol; dipropylene glycol monomethyl ether; dipropylene glycol dimethyl ether; dipropylene glycoldi-n-butyl ether; N-methylpyrrolidone; diphenylmethane; diisopropylnaphthalene; petroleum fractions such as

products (available from Exxon) ; alkylphenols, such as tert-butylphenol, nonylphenol, dodecylphenol and 8, 11, 14-pentadecatrienylphenol; styrenated phenol; bisphenols; aromatic hydrocarbon resins especially those containing phenol groups, such as ethoxylated or propoxylated phenols; adipates; sebacates; phthalates; benzoates; organic phosphoric or sulfonic acid esters; and sulfonamides.

The above aside, it is preferred that said non-reactive diluents constitute less than 10 wt. %, in particular less than than 5 wt. %or less than 2 wt. %, based on the total weight of the composition.

For completeness, the compositions of the present invention may comprise one or more monoamines, such as hexylamine and benzylamine.

ILLUSTRATIVE EMBODIMENT OF THE INVENTION

Without intention to limit the present invention, good results have been obtained where the photo-curable composition for use in additive manufacturing comprises:

from 10 to 50 wt. %of (a) at least one epoxidized polyolefin having a residual olefinic unsaturation of from 0.01 to 0.5 meq/g polymer and which is selected from the group consisting of epoxidized polybutadiene, epoxidized polyisoprene and epoxidized copolymers of butadiene or isoprene with styrene, said epoxidized polyolefin being further characterized by: an epoxy oxygen content of from 5 to 10 wt. %; an epoxy equivalent weight of from 100 to 500 g/eq; a hydroxyl group content of from 1 to 3 percent by weight; and, a number average molecular weight (Mn) of from 1000 to 5000 g/mol;

from 20 to 70 wt. %of (b) at least one polyepoxide compound selected from the group consisting of: glycidyl ethers of polyhydric alcohols; gycidyl ethers of polyhydric phenols; and, glycidyl esters of polycarboxylic acids;

from 5 to 20 wt. %of (c) polyester of a thiocarboxylic acid selected from the group consisting of pentaerythritol tetramercapto-acetate (PETMP) , trimethylolpropane trimercaptoacetate (TMPMP) , glycol dimercaptoacetate and mixtures thereof;

from 0.05 to 2.0 wt. %of d) free radical photoinitiator compound selected from the group consisting of: benzoylphosphine oxides; aryl ketones; benzophenones; hydroxylated ketones; 1-hydroxyphenyl ketones; ketals; metallocenes; and combinations thereof; and,

from 1 to 50 wt. %of e) said polyamine having at least two amine hydrogens reactive toward epoxide groups.

PREPARATION OF THE COMPOSITIONS

To form a composition, the above described parts are brought together and mixed. As is known in the art, to form one component (1K) curable compositions, the elements of the composition are brought together and homogeneously mixed under conditions which inhibit or prevent the reactive components from reacting: as would be readily comprehended by the skilled artisan, this might include mixing conditions which limit or prevent exposure to moisture or irradiation or which limit or prevent the activation of a constituent latent catalyst. As such, it will often be preferred that the curative elements are not mixed by hand but are instead mixed by machine –a static or dynamic mixer, for example -in pre-determined amounts under anhydrous conditions without intentional photo-irradiation.

For the two component (2K) compositions, the reactive components are brought together and mixed in such a manner as to induce the hardening thereof. For both one (1K) and two (2K) component compositions, the reactive compounds should be mixed under sufficient shear forces to yield a homogeneous mixture. It is considered that this can be achieved without special conditions or special equipment. That said, suitable mixing devices might include: static mixing devices; magnetic stir bar apparatuses; wire whisk devices; augers; batch mixers; planetary mixers; C.W. Brabender or

style mixers; and, high shear mixers, such as blade-style blenders and rotary impellers.

For small-scale liner applications in which volumes of less than 2 liters will generally be used, the preferred packaging for the two component (2K) compositions will be side-by-side double cartridges or coaxial cartridges, in which two tubular chambers are arranged alongside one another or inside one another and are sealed with pistons: the driving of these pistons allows the components to be extruded from the cartridge, advantageously through a closely mounted static or dynamic mixer. For larger volume applications, the two components of the composition may advantageously be stored in drums or pails: in this case the two components are extruded via hydraulic presses, in particular by way of follower plates, and are supplied via pipelines to a mixing apparatus which can ensure fine and highly homogeneous mixing of the hardener and binder components. In any event, for any package it is important that the binder component be disposed with an airtight and moisture-tight seal, so that both components can be stored for a long time, ideally for 12 months or longer.

Non-limiting examples of two component dispensing apparatuses and methods that may be suitable for the present invention include those described in U.S. Patent No. 6,129,244 and US Patent No. 8,313,006.

Where applicable, two (2K) component compositions should broadly be formulated to exhibit an initial viscosity -determined immediately after mixing, for example, up to two minutes after mixing -of less than 200000 mPa·s, for instance less than 100000 mPa. s, at 25℃. Independently of or additional to said viscosity characteristics, the two (2K) component composition should be formulated to be bubble (foam) free upon mixing and subsequent curing. Moreover, the two component (2K) composition should further be formulated to demonstrate at least one, desirably at least two and most desirably all of the following properties: i) a long pot life, typically of at least 30 minutes and commonly of at least 60 or 120 minutes, which pot life should be understood herein to be the time after which the viscosity of a mixture at 20℃ will have risen to more than 50,000 mPas; ii) a maximum exotherm temperature of no greater than 120℃, preferably no greater than 100℃ and more preferably no greater than 80℃; and, iii) a Shore A hardness of at least 50, preferably at 60 and more preferably at least 70 after being cured and stored for 7 days at room temperature and 50%relative humidity.

METHODS AND APPLICATIONS

In accordance with the broadest process aspects of the present invention, the above described compositions are applied to a substrate and then cured in situ. Prior to applying the compositions, it is often advisable to pre-treat the relevant surfaces to remove foreign matter there from: this step can, if applicable, facilitate the subsequent adhesion of the compositions thereto. Such treatments are known in the art and can be performed in a single or multi-stage manner constituted by, for instance, the use of one or more of: an etching treatment with an acid suitable for the substrate and optionally an oxidizing agent; sonication; plasma treatment, including chemical plasma treatment, corona treatment, atmospheric plasma treatment and flame plasma treatment; immersion in a waterborne alkaline degreasing bath; treatment with a waterborne cleaning emulsion; treatment with a cleaning solvent, such as carbon tetrachloride or trichloroethylene; and, water rinsing, preferably with deionized or demineralized water. In those instances where a waterborne alkaline degreasing bath is used, any of the degreasing agent remaining on the surface should desirably be removed by rinsing the substrate surface with deionized or demineralized water.

In some embodiments, the adhesion of the coating compositions of the present invention to the preferably pre-treated substrate may be facilitated by the application of a primer thereto. Whilst the skilled artisan will be able to select an appropriate primer, instructive references for the choice of primer include but are not limited to: US Patent No. 3,671,483; US Patent No. 4,681,636; US Patent No. 4,749,741; US Patent No. 4,147,685; and, US Patent No. 6,231,990.

The compositions are then applied to the preferably pre-treated, optionally primed surfaces of the substrate. And, as noted above, in a preferred embodiment of the present invention, this application is effected by additive manufacturing methods.

Most broadly, two techniques are known for additive manufacturing are known and may be utilized in the present invention: a first in which new layers are formed at the top surface of the growing object; a second method in which new layers are formed at the bottom surface of the growing object. The teaching of the following documents may be instructive in the regard: US Patent No. 5,236,637 (Hull) ; US Patent No. 7,438,846; US Patent No. 7,892,474; US 2013/0292862 A1 (Joyce) ; US 2013/0295212 A1 (Chen et al. ) ; and Pan et al., J. Manufacturing Sci. and Eng. 134, 051011-1 (Oct. 2012) .

In a typical mode of application, the method of the present invention comprises the step of printing the above defined composition with a 3D printer, irradiating the composition so that it at least partially cures thereon to form a coating layer on the substrate. The resultant layer formed by 3D printing is desirably both continuous and of consistent thickness.

In an important embodiment, the present method incorporates the steps of: i) providing a carrier and an optically transparent member having a movable build surface, said carrier and build surface defining a build region there between; ii) within said build region, applying by 3D printing a first layer of the composition as defined herein above and in the appended claims; iii) irradiating said build region through said optically transparent member to at least partially cure that first layer; iv) applying a subsequent layer of said composition as defined herein above and in the appended claims by 3D printing on the at least partially cured layer; and, v) irradiating said build region through said optically transparent member to at least partially cure that subsequent layer. In an iterative process, steps iii) and iv) may be performed and repeated so as to dispose second, third, fourth and further layers on the substrate.

As used herein, the term "at least partially cured" means that curing of the curable composition has been initiated and that, for example, cross-linking of components of the composition has commenced. The term encompasses any amount of cure upon application of the curing condition, from the formation of a single cross-link to a fully cross-linked state. Obviously, the rate and mechanism with which the composition cures is contingent on various factors, including the components thereof, functional groups of the components and the parameters of the curing condition.

At least partial solidification of a given coating layer is generally indicative of cure or drying. However, both drying and cure may be indicated in other ways including, for instance, a viscosity change of the coating layer, an increased temperature of that coating layer and /or a transparency /opacity change of that coating layer. It may be desirable for the or each step iii) of the above described application process to be commenced only when the at least partially cured or partially dried preceding layer can substantially retain its shape upon exposure to ambient conditions. By "substantially retains its shape" it is meant that at least 50%by volume, and more usually at least 80%or 90%by volume of the at least partially cured or dried layer retains its shape and does not flow or deform upon exposure to ambient conditions for a period of 5 minutes. Under such circumstances, gravity should not therefore substantially impact the shape of the at least partially cured or partially dried layer upon exposure to ambient conditions.

For completeness, the shape of the at least partially dried or at least partially cured layer will impact whether said layer substantially retains its shape. For example, when said layer is rectangular or has another simplistic shape, the at least partially cured or dried layer may be more resistant to deformation at even lesser levels of cure or even lesser degrees of drying than layers having more complex shapes.

In certain embodiments, the 3D-printing of the subsequent layer (step iii) ) occurs before an at least partially cured layer has reached a final cured state, nominatively while the layer is still "green. " In such embodiments, printing of the layers may be considered "wet-on-wet" such that the adjacent layers at least physically bond, and may also chemically bond, to one another. For example, it is possible that components in each of the first and subsequent layers can chemically cross-link/cure across the print line, which effect can be beneficial to the longevity, durability and appearance of the 3D article. Importantly, the distinction between partial cure and a final cured state is whether the partially cured layer can undergo further curing or cross-linking. This does not actually preclude functional groups being present in the final cure state but such groups may remain un-reacted due to steric hindrance or other factors.

In the aforementioned iterative process, the thickness, width, shape and continuity of each layer may be independently selected such that the or each preceding and subsequent layer may be the same or different from one another in one or more of these regards. For example, a given subsequent layer may only contact a portion of an exposed surface of the at least partially cured or dried preceding layer: depending on the desired shape of the coating layer, the subsequent layer may build on that layer selectively.

The thickness and /or width tolerances of the or each layer may depend on the 3D printing process used, with certain printing processes having high resolutions and others having low resolutions. Whilst the present disclosure is not limited to any particular dimensions of any of the layers, it is recommended that the compositions be applied to a wet film thickness of from 10 to 5000 μm or from 10 to 1000μm. The application of thinner layers within this range is more economical but great control must be exercised in applying thinner layers to avoid the formation of discontinuous cured or dried films.

There is no particular intention to limit the types of 3D printers and/or 3D printing methodologies which may be utilized in the present invention. For instance, a suitable 3D printer may be selected from: fused filament fabrication printers; selective laser sintering printers; selective laser melting printers; stereolithography printers; powder-bed (binder jet) printers; material jet printers; direct metal laser sintering printers; electron beam melting printer; laminated object manufacturing deposition printers; directed energy deposition printers; laser powder forming printers; polyjet printers; ink-jetting printers; material jetting printers; and, syringe extrusion printer. It is further noted that the 3D printer may be independently selected during each printing step of an iterative process when employed in the present method: thus, if desired, each printing step of an iterative process may utilize a different 3D printer such that different characteristics are imparted with respect to distinct layers.

For solvent borne compositions which yield a film upon drying, any required drying step can of course be accelerated by the application of an elevated temperature, for instance a temperature in the range of from 50℃ to 150℃ or from 50℃ to 120℃. Conduction, convection and/or induction heating methods may be employed in this context. The use of forced air in conjunction with heating may be beneficial to the drying process in certain circumstances.

As will be recognized by the skilled artisan, any requisite step or, in an iterative process, each drying step for a solvent borne composition need not be performed in a single, continuous manner. It can be advantageous, for example, to apply heat in a first stage up until the onset of coating coalescence and while the coating composition remains fluid-like: in such a state, the coating may hold fillers, including microspheres in place, but will also flow sufficiently to enable it to become leveled on the substrate. Heat may then subsequently be applied again to a temperature sufficient to further drive the solvent off from the coating composition.

Conventionally, the energy source used to cure radiation curable compositions will emit at least one of ultraviolet (UV) radiation, infrared (IR) radiation, visible light, X-rays, gamma rays, or electron beams (e-beam) . Subsequent to their application by 3D-printing, the radiation curable coating compositions may typically be activated in less than 5 minutes, and commonly between 1 and 60 seconds –for instance between 3 and 12 seconds -when irradiated using commercial curing equipment.

Irradiating ultraviolet light should typically have a wavelength of from 150 to 600 nm and preferably a wavelength of from 200 to 450 nm. Useful sources of UV light include, for instance, extra high pressure mercury lamps, high pressure mercury lamps, medium pressure mercury lamps, low intensity fluorescent lamps, metal halide lamps, microwave powered lamps, xenon lamps, UV-LED lamps and laser beam sources such as excimer lasers and argon-ion lasers.

Where an e-beam is utilized to cure the layer (s) , standard parameters for the operating device may be: an accelerating voltage of from 0.1 to 100 keV; a vacuum of from 10 to 10 ^-3 Pa; an electron current of from 0.0001 to 1 ampere; and, power of from 0.1 watt to 1 kilowatt.

The amount of radiation necessary to cure an individual, radiation curable coating composition will depend on a variety of factors including the angle of exposure to the radiation and the thickness of a coating layer. Broadly however, a curing dosage of from 5 to 5000 mJ/cm ² may be cited as being typical: curing dosages of from 50 to 500 mJ/cm ², such as from 50 to 400 mJ/cm ² may be considered highly effective.

The curing of the so-printed curable compositions should typically occur at temperatures in the range of from -10℃ to 120℃, preferably from 0℃ to 70℃, and in particular from 20℃ to 60℃. The temperature that is suitable depends on the specific compounds present and the desired curing rate and can be determined in the individual case by the skilled artisan, using simple preliminary tests if necessary. Of course, curing at temperatures of from 10℃ to 35℃ or from 20℃ to 30℃ are especially advantageous as they obviate the requirement to substantially heat or cool the mixture from the usually prevailing ambient temperature. Where applicable, however, the temperature of the curable compositions may be raised above the mixing temperature and /or the application temperature using conventional means, including microwave induction.

The following example is illustrative of the present invention and is not intended to limit the scope of the invention in any way.

EXAMPLE

The following compounds are employed in the Example:

DER ^TM 331: Bisphenol-F epoxy resins available from Dow Chemical Company

JP-400: Epoxidized polybutadiene available from Nisso Soda Company Limited

Ancamine 2264: Polycycloaliphatic polyamine available from Evonik Corporation

Darocur 1173: 2-Hydroxy-2-methylpropiophenone available from Sigma Aldrich

PETMP: Pentaerythritol tetrakis (3-mercaptopropionate) available from Sigma Aldrich

The following composition as defined in Table 1 was prepared under mixing using a rotation revolution mixer, Thinky A-250:

Table 1

Ingredient	Percentage by Weight of the Composition (%w/w)
DER 331	59.0
JP-400	30.0
Ancamine 2264	10.0
PETMP	20.0
Darocur 1173	1.0

The composition was applied to a rigid planar Teflon substrate using a stereolithography (SLA) additive manufacturing technique employing a Formlabs Form 2 3D-printer.

The printed composition had an initial viscosity of 40000 cps at 25℃ and was exposed to UV light irradiation for 5 min and then left at room temperature to obtain the rigid, cured resin. The composition was allowed to dry in air to a dry film thickness of from 400 to 500 μm: the dried coating layer was characterized by a Shore D hardness of 75 ± 3.

In view of the foregoing description and example, it will be apparent to those skilled in the art that equivalent modifications thereof can be made without departing from the scope of the claims.

Claims

A photo-curable composition for use in additive manufacturing, said composition comprising:

a) at least one epoxidized polyolefin which is characterized by a residual olefinic unsaturation of from 0.01 to 0.5 meq/g polymer and which is selected from the group consisting of epoxidized alicyclic polyolefin and epoxidized aliphatic polyolefin;

optionally b) at least one epoxide compound which is distinct from the epoxidized polyolefin (a) ;

c) at least one compound which has at least two reactive mercapto-groups per molecule;

d) at least one free radical photoinitiator compound; and,

e) at least one polyamine having at least two amine hydrogens reactive toward epoxide groups.
The composition according to claim 1 comprising from 5 to 90 wt. %, preferably from 10 to 80 wt. %of a) said at least one epoxidized polyolefin, based on the total weight of the composition.
The composition according to claim 1 or claim 2, wherein said at least one epoxidized polyolefin is further characterized by an epoxy oxygen content of from 5 to 10 percent by weight, an epoxy equivalent weight of 100 to 2,000 g/eq. and a hydroxyl group content of from 1 to 3 percent by weight.
The composition according to any one of claims 1 to 3, wherein said at least one epoxidized polyolefin is further characterized by a number average molecular weight (Mn) of from 1000 to 10000 g/mol.
The composition according to any one of claims 1 to 4 comprising b) said at least one epoxide compound in an amount up to 80 wt. %, based on the weight of the composition.
The composition according to any one of claims 1 to 5 comprising a polyepoxide compound having an epoxy equivalent weight of from 100 to 700 g/eq.
The composition according to any one of claims 1 to 6 comprising from 1 to 40 wt. %, preferably from 3 to 30 wt. %of c) said at least one mercapto-group containing compound.
The composition according to any one of claims 1 to 7, wherein said free radical photoinitiator d) is selected from the group consisting of: benzoylphosphine oxides; aryl ketones; benzophenones; hydroxylated ketones; 1-hydroxyphenyl ketones; ketals; metallocenes; and combinations thereof.
The composition according to any one of claims 1 to 7, wherein said free radical photoinitiator d) is selected from the group consisting of: benzoin dimethyl ether; 1-hydroxycyclohexyl phenyl ketone; benzophenone; 4- chlorobenzophenone; 4-methylbenzophenone; 4-phenylbenzophenone; 4, 4'-bis (diethylamino) benzophenone; 4, 4'-bis (N, N'-dimethylamino) benzophenone (Michler's ketone) ; isopropylthioxanthone; 2-hydroxy-2-methylpropiophenone; 2-methyl-4- (methylthio) -2-morpholinopropiophenone; methyl phenylglyoxylate; methyl 2-benzoylbenzoate; 2-ethylhexyl 4- (dimethylamino) benzoate; ethyl 4- (N, N-dimethylamino) benzoate; phenylbis (2, 4, 6-trimethylbenzoyl) phosphine oxide; diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide; ethyl phenyl (2, 4, 6-trimethylbenzoyl) phosphinate; and, combinations thereof.
The composition according to any one of claims 1 to 9 comprising from 0.05 to 5.0 wt. %, preferably from 0.05 to 2.0 wt. %of d) said at least one free radical photoinitiator compound, based on the weight of the composition.
The composition according to any one of claims 1 to 10, wherein said at least one polyamine contains primary and /or secondary amine groups and has an equivalent weight per primary or secondary amine group of not more than 150, preferably not more than 125.
A photo-curable composition for use in additive manufacturing according to claim 1, said composition comprising:

from 10 to 50 wt. %of (a) at least one epoxidized polyolefin having a residual olefinic unsaturation of from 0.01 to 0.5 meq/g polymer and which is selected from the group consisting of epoxidized polybutadiene, epoxidized polyisoprene and epoxidized copolymers of butadiene or isoprene with styrene, said epoxidized polyolefin being further characterized by: an epoxy oxygen content of from 5 to 10 wt. %; an epoxy equivalent weight of from 100 to 500 g/eq; a hydroxyl group content of from 1 to 3 percent by weight; and, a number average molecular weight (Mn) of from 1000 to 5000 g/mol;

from 20 to 70 wt. %of (b) at least one polyepoxide compound selected from the group consisting of: glycidyl ethers of polyhydric alcohols; gycidyl ethers of polyhydric phenols; and, glycidyl esters of polycarboxylic acids;

from 5 to 20 wt. %of (c) polyester of a thiocarboxylic acid selected from the group consisting of pentaerythritol tetramercapto-acetate (PETMP) , trimethylolpropane trimercaptoacetate (TMPMP) , glycol dimercaptoacetate and mixtures thereof;

from 0.05 to 2.0 wt. %of d) free radical photoinitiator compound selected from the group consisting of: benzoylphosphine oxides; aryl ketones; benzophenones; hydroxylated ketones; 1-hydroxyphenyl ketones; ketals; metallocenes; and combinations thereof; and,

from 1 to 50 wt. %of e) said polyamine having at least two amine hydrogens reactive toward epoxide groups.
The composition according to any one of claims 1 to 12 characterized by a molar ratio of epoxy-reactive groups to epoxy groups from 0.95: 1 to 1.5: 1, preferably from 0.95: 1 to 1.1: 1.
A method for forming a three dimensional object, said method comprising:

i) providing a carrier and an optically transparent member having a movable build surface, said carrier and build surface defining a build region there between;

ii) within said build region, applying by 3D printing a first layer of the composition as defined in any one of claims 1 to 13;

iii) irradiating said build region through said optically transparent member to at least partially cure that first layer;

iv) applying a subsequent layer of said composition by 3D printing on the at least partially cured layer; and,

v) irradiating said build region through said optically transparent member to at least partially cure that subsequent layer.
An iterative method according to claim 14 for forming a three dimensional object, wherein said steps iv) and v) are performed and repeated so as to dispose second, third, fourth and further layers within the build region.