Photocurable compositions for three-dimensional investment pattern casting and their uses

Abstract

A thermoreversible photocurable composition is disclosed that has high strength at low temperatures but melts at high temperatures, making it well suited as an investment casting pattern composition.

Description

[Technical Field]

[0001] The present invention relates to photocurable compositions that polymerize to a solid state when exposed to UV light and then soften and melt when heated, making them particularly useful for producing three-dimensional investment patterns. [Background technology]

[0002] Investment casting is a method of creating complex objects in a variety of industries by (1) creating a three-dimensional pattern, (2) creating a shell over the three-dimensional pattern using a slurry composition, (3) removing the three-dimensional pattern from the shell using heat, (4) forming an object to be molded within the investment shell where the pattern was removed, and (5) removing or destroying the shell from the object. Investment casting allows for the production of complex objects with excellent dimensional accuracy and excellent as-cast surface finish. Articles such as jewelry, turbine rotors, gears, electronic device housings, valves, electronic components, and medical devices have been cast from patterns.

[0003] The two most common methods for creating three-dimensional patterns in investment casting technology are (1) fused deposition modeling (FDM) and (2) stereolithography (SLA) / digital light processing (DLP). Investment patterns created with FDM materials melt at temperatures between 100 and 200°C, making them easier to remove, but they lack precision and have lower mechanical properties than SLA technology. Investment patterns made with SLA and DLP resins have superior precision and mechanical properties, but because their chemical composition does not melt, they must be baked at temperatures above 200°C. This high-temperature baking process can cause thermal expansion of the investment pattern, potentially resulting in cracks in the shell. In investment casting, maintaining the integrity of the shell is crucial to the formation of the final object.

[0004] The present invention fills a need in the art for high precision, high strength, and easily removable three-dimensional investment patterns. Summary of the Invention [Means for solving the problem]

[0005] The present invention provides a thermoreversible photocurable composition for three-dimensional investment casting patterns in investment casting processes that require strong mechanical strength when formed, but soften and melt when heated.

[0006] In one embodiment, the investment casting pattern composition comprises: A) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value of more than about 25°C; C) A thermoreversible crosslinker with UV curing function and thermoreversible covalent bond; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, an irreversible chain transfer agent, an antioxidant, a hindered amine light stabilizer, or a mixture thereof; Includes.

[0007] In another embodiment, the present invention provides: A) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value of more than about 25°C; C) Oligomers with two or more furan-maleimide Diels-Alder adducts; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, an irreversible chain transfer agent, an addition-fragmentation chain transfer agent (AFCT), an antioxidant, a hindered amine light stabilizer, or a mixture thereof; The present invention relates to a photocurable composition comprising:

[0008] The photocurable composition may be used as the basis for an investment casting pattern to form an object using an investment casting process. The photocurable composition maintains high mechanical strength at temperatures below about 130°C due to thermoreversible bonds in the composition, and softens and melts at temperatures above about 130°C.

[0009] In yet another embodiment: 1) aA) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value of more than about 25°C; C) A thermoreversible crosslinker with UV curing function and thermoreversible covalent bond; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, an irreversible chain transfer agent, an antioxidant, a hindered amine light stabilizer, or a mixture thereof; preparing a photocurable composition comprising: b. photocuring the photocurable composition to form a cured three-dimensional pattern having a first side and a second side, the second side being an outermost side; 2) applying a slurry solution onto the second surface of the hardened three-dimensional pattern; 3) drying, curing or solidifying the slurry solution to form a shell on the cured pattern; 4) heating the hardened three-dimensional pattern and the shell to a temperature sufficient to soften the hardened three-dimensional pattern; and 5) separating the hardened three-dimensional pattern from the shell; The present invention relates to a method for manufacturing an investment casting shell, including:

[0010] In another embodiment, the present invention provides: 1) combining and mixing the following ingredients to form a mixture: A) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value of more than about 25°C; C) A thermoreversible crosslinker with UV curing function and thermoreversible covalent bond; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, an irreversible chain transfer agent, an antioxidant, a hindered amine light stabilizer, or a mixture thereof; 2) applying the mixture onto a substrate or depositing the mixture as a free-standing 3D structure; and 3) photocuring the mixture to harden the removable photocurable composition; The present invention relates to a method for producing a removable photocurable composition, comprising: 4) The removable photocurable material can be removed by heating it at a temperature of about 130°C to about 250°C. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a cured photocurable composition. [Figure 2] 2A-2D are differential scanning calorimetry (DSC) curves of various compositions. DETAILED DESCRIPTION OF THE INVENTION

[0012] Investment casting is a process in which a pattern is surrounded by a slurry to create an investment shell. The shell is then separated from the pattern (typically by heating). Once separated, the investment shell is used as the basis for forming articles such as turbine rotors, gears, electronics housings, valves, electronic components, and medical devices.

[0013] The three-dimensional object is photocurable by actinic radiation, which is electromagnetic radiation capable of causing a photochemical reaction.

[0014] As used herein, the term melting point of a substance refers to the temperature at which the substance changes state from solid to liquid. At the melting point, the solid and liquid phases exist in equilibrium. As used herein, the term softening point refers to the temperature at which a substance softens, particularly the temperature at which an amorphous substance begins to soften.

[0015] As used herein, a monomer is defined as a molecule that can be polymerized into a polymer. The monomer may be a monofunctional monomer having a single functional polymerizable group, or a polyfunctional monomer having two or more functional polymerizable groups. The molecular weight of the monomer may be low (e.g., about 100 to about 1,000 daltons), medium (e.g., about 1,000 to about 5,000 daltons), or high (e.g., about 5,000 to about 20,000 daltons).

[0016] The present invention provides a thermoreversible, photocurable investment pattern composition. The pattern must be formed in a way that maintains the integrity of both the pattern itself and the shell during the heating and removal process. In one embodiment, the investment casting pattern composition comprises: A) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value of more than about 25°C; C) A thermoreversible crosslinker with UV curing function and thermoreversible covalent bond; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, a reversible chain transfer agent (RAFT), an antioxidant, a hindered amine light stabilizer, or a mixture thereof; Includes.

[0017] Investment casting pattern compositions require a combination of cationically or radically curable monomers to form the polymer backbone. The combination of Monomer A, which has a glass transition temperature value below about 25° C., and Monomer B, which has a glass transition temperature value above about 25° C., provides a polymeric network suitable for investment patterns.

[0018] The backbone is formed from at least two monomers, each of which independently has a functional group selected from (meth)acrylate, acrylate, vinyl ester, vinyl, ether, allyl, N-vinyl, vinylamide, thiol, (meth)acrylamide, vinyl carbonate, acryloyl, vinyl carbamate, maleimide, cyanoacrylate, thiol and epoxide, styrene, vinyl halide, acrylonitrile, nadimide, itaconimide, and vinyl ether. The term "backbone" is intended to refer to the chemical moieties to which the functional groups are attached or the chemical moieties present between the functional groups. In another embodiment, the backbone is formed from a single monomer.

[0019] Monomer A has a glass transition (Tg) temperature of less than about 25°C, preferably less than about 0°C, and most preferably less than about -15°C, and contains at least one of the above-mentioned reactive groups. The functional group of Monomer A is preferably a methacrylate or acrylate. Particularly preferred examples of Monomer A include lauryl acrylate (Tg = 15°C), lauryl methacrylate (Tg = -65°C), isodecyl acrylate (Tg = -58°C), isodecyl methacrylate (Tg = -70°C), 2-propylheptyl acrylate (Tg = -68°C), isobutyl acrylate (Tg = -24°C), ethyl diglycol acrylate (Tg = -53°C), heptadecyl acrylate (Tg = -64°C), and 4-hydroxybutyl acrylate (Tg = -65°C).

[0020] Monomer A is present in the range of about 1% to about 30% by weight of the total investment casting pattern composition, preferably about 3% to about 15% by weight.

[0021] Monomer B has a glass transition temperature value greater than about 25° C., preferably greater than 50° C., more preferably greater than 75° C. It is particularly preferred that Monomer B comprises a methacrylate, acrylate, vinyl ester, vinyl, ether, allyl, N-vinyl, vinylamide, acrylamide, vinyl carbonate, acryloyl, vinyl carbamate, maleimide, cyanoacrylate, thiol, or epoxide functional group.

[0022] Examples of reactive groups for the monomer B group include isobornyl acrylate (Tg=95°C), isobornyl methacrylate (Tg=110°C), N-vinyl caprolactam (Tg=125°C), cyclohexyl methacrylate (Tg=92°C), hydroxyethyl methacrylate (Tg=55°C), hydroxypropyl methacrylate (Tg=76°C), phenyl methacrylate (Tg=110°C), methacrylic acid (Tg=228°C), acrylamide (Tg=165°C), N-vinylpyrrolidone (Tg=150°C), acryloylmorpholine (Tg=145°C), and N,N-dimethylacrylamide (Tg=119°C).

[0023] Monomer B is present in the range of about 10% to about 75% by weight of the total investment casting pattern composition, preferably about 20% to about 60% by weight, and more preferably about 25% to about 55% by weight.

[0024] Combining two monomers with different Tg's can provide a balanced combination of high strength, high ductility, and high modulus of elasticity. If the Tg of the monomer combination used in investment casting is too high (e.g., above 100°C), the resulting polymer will exhibit high viscosity upon heating and will be difficult to soften. In contrast, if the Tg of the monofunctional monomer used is too low (e.g., below 20°C), the mechanical properties of the resulting polymer will be poor, and the investment pattern will be distorted by applied stress.

[0025] Combining the above range of monomers with a thermo-reversible crosslinker provides sufficient mechanical and physical properties in terms of softness, tensile strength, and moldability while maintaining meltability.

[0026] The elastic modulus of the backbone, including the thermoreversible crosslinker, monomer A and monomer B should be greater than about 10 MPa Young's modulus according to ASTM D638.

[0027] The investment casting pattern composition further comprises a thermoreversible crosslinker having UV-curable functional groups and thermoreversible covalent bonds. The thermoreversible crosslinker comprises: a) a bismaleimide or a compound having two or more maleimide groups; b) furfuryl methacrylate or furfuryl arylate; It is produced by the reaction: The molar ratio of a to b is 1:0.5 to 1:2.

[0028] In one embodiment, the thermoreversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of furfuryl methacrylate. In another embodiment, the thermoreversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of furfuryl acrylate. In yet another embodiment, the thermoreversible crosslinker is prepared by reacting a starting material containing two or more maleimide groups with 0.5 to 1 molar equivalent of furfuryl methacrylate per maleimide. In another embodiment, the thermoreversible crosslinker is prepared by reacting a starting material containing two or more maleimide groups with 0.5 to 1 molar equivalent of furfuryl acrylate per maleimide. In another embodiment, the thermoreversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one methacrylate group. In yet another embodiment, the thermally reversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one acrylate group.

[0029] The Diels-Alder reaction forms an adduct between bismaleimide and furfuryl acrylate at temperatures up to about 80°C. The adduct is thermoreversible through a reverse Diels-Alder reaction at temperatures between about 80°C and about 180°C. The adduct forms when the temperature rises to about 80°C, and the bond dissociates when the adduct reaches the reversible temperature between about 80°C and 180°C. The best way to dissociate the adduct is to hold it above the reversible temperature for the shortest possible time. The temperature and time can be determined by experimentation by those skilled in the art. For example, a short time at a high temperature or a long time at a low temperature.

[0030] [ka]

[0031] The thermoreversible crosslinker forms a network reaction of polymers with pendant furan and / or maleimide heterocycles.

[0032] [ka]

[0033] The stereochemistry and actual location of the furan or bismaleimide within the polymer chain determines its reactivity.

[0034] In one example, the thermoreversible crosslinker is a furan-maleimide Diels-Alder adduct of bismaleimide (1,1'-(methylenedi-4,1-phenylene)bismaleimide), which reacts with two molar equivalents of furfuryl methacrylate to form (methylenebis(4,1-phenylene))bis(1,3-dioxo-2,3,3a,4,7,7a-hexahydro-1H-4,7-epoxyisoindole-2,5-diyl)bis(2-methylacrylate).

[0035] In yet another embodiment, the thermoreversible crosslinker is prepared by reacting a polyimide having pendant maleimide functional groups with a trifuran derivative.

[0036] In one embodiment, the thermoreversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of furfuryl glycidyl ether. In another embodiment, the thermoreversible crosslinker is prepared by reacting a starting material containing two or more maleimide groups with 0.5 to 1 molar equivalent of furfuryl glycidyl ether per maleimide.

[0037] In another embodiment, the thermally reversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one epoxy group.

[0038] In another embodiment, the thermally reversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one acrylamide group.

[0039] In another embodiment, the thermally reversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one methacrylamide group.

[0040] In another embodiment, the thermally reversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one vinyl group.

[0041] In another embodiment, the thermally reversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one vinyl group.

[0042] In another embodiment, the thermally reversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one vinyl ester group.

[0043] In another embodiment, the thermally reversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one vinyl ether group.

[0044] In another embodiment, the thermally reversible crosslinker is prepared by reacting a bismaleimide with two molar equivalents of a reactant containing one furfuryl group and one cyanoacrylate group.

[0045] The thermoreversible crosslinker can have a variety of molecular weight ranges, including low molecular weight (about 500 to about 1,000 daltons), medium molecular weight (about 1,000 to about 5,000), and high molecular weight (5,000 to about 10,000 daltons). Those skilled in the art can select an appropriate thermoreversible crosslinker with an appropriate molecular weight range depending on factors such as viscosity, reaction rate, and miscibility.

[0046] The thermoreversible crosslinking agent is present in an amount of from about 10% to about 90% by weight, preferably from about 20% to about 50% by weight of the total investment casting pattern composition.

[0047] The investment casting pattern composition also includes a photoinitiator, including both Type I and Type II photoinitiators. Suitable photoinitiators include triazines, ketones, peroxides, diketones, azides, azo derivatives, disulfide derivatives, disilane derivatives, thiol derivatives, diselenide derivatives, diphenylditelluride derivatives, digermane derivatives, distannane derivatives, carbogermanium compounds, carbon-silicon derivatives, sulfur-carbon derivatives, sulfur-silicon derivatives, peresters, Barton's ester derivatives, hydroxamic and thiohydroxamic acids and esters, organic borates, organometallic compounds, titanocenes, chromium complexes, aluminate complexes, carbon-sulfur or sulfur-sulfur iniferter compounds, oxyamines, aldehydes, acetals, silanes, phosphorus-containing compounds, borane complexes, thioxanthone derivatives, coumarins, anthraquinones, fluorenones, and ferrocenium salts. In one embodiment, the photoinitiator is a Norrish Type I initiator selected from 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 1-hydroxycyclohexyl-phenyl ketone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO), or ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (TPO-L), available from IGM Resins under the registered trademark OMNIPOL TP series.

[0048] Commercially available photoinitiators include OMIRAD TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide), OMIRAD 184 (1-hydroxycyclohexylphenyl ketone), the Irgacure series, the Chemicure series, and the Daido UV-cure series.

[0049] When used, the photoinitiator is present in an amount of from about 0.01% to about 15% by weight of the total composition.

[0050] The investment casting pattern composition may contain a thermal initiator, but does not require a thermal initiator.

[0051] The investment casting pattern composition may further include additives including chain transfer agents, irreversible chain transfer agents, antioxidants, hindered amine light stabilizers, amine synergists (both reactive and non-reactive), optical brighteners, ultraviolet light screeners, fillers including both inorganic and organic fillers, dyes and pigments, waxes and wax-like additives, plasticizers, or mixtures thereof.

[0052] Chain transfer agents include free radical living polymerization catalysts, catalytic chain transfer agents, reversible addition-fragmentation chain transfer (RAFT) agents, and iodine transfer agents for polymerization.

[0053] Particularly preferred additives are addition-fragmentation chain transfer agents. Exemplary additives include allyl sulfide, allyl phenyl sulfone, ethyl 2-tosyloxyacrylate, ethyl 2-(1-hydroxyperoxyethyl)propenoate, mono-β-allyl sulfone, α-(benzyloxy)styrene, carbon tetrachloride, carbon tetrabromide, bromotrichloromethane, 4-methylbenzenethiol, pentaphenylethane, tert-nonyl mercaptan, 4,4'-thiobisbenzenethiol, n-octyl mercaptan, thioglycolic acid, and mixtures thereof. Addition-fragmentation chain transfer agents can design and aid in the reversibility of investment casting.

[0054] The Diels-Alder reaction of bismaleimide and furfuryl acrylate undergoes a side reaction of forming branches in the polymer backbone under free radical polymerization. This increases the molecular weight and affects irreversible crosslinking reactions during investment casting. This avoids the branching side reaction of the polymer and effectively reduces the molecular weight. A chain transfer agent is added to the investment casting composition. The addition of this chain transfer agent softens the polymer at approximately 130°C in the investment casting composition. This softens the investment casting composition sufficiently to allow it to be separated from the master pattern by heat.

[0055] Figure 1 is a schematic diagram of a cured photocurable composition. The squares represent hard segments formed from high Tg monomers. The hard segments provide rigidity and strength to the cured product. The soft segments formed from low Tg monomers are represented by lines and provide flexibility and toughness to the cured product. The thermoreversible crosslinkers are represented as spheres connected to the hard segments, which can be debonded and separated by heat. The chain transfer agent can adjust the molecular weight of the polymer and shorten the unit length (n) of the polymer. Under sufficient heat exposure, the cured photocurable composition softens and melts due to the separation of the thermoreversible crosslinkers and the attainment of the glass transition temperature.

[0056] Exemplary antioxidants include butylated hydroxytoluene, 4-methoxyphenol, 4,4′-thiobis(2-tert-butyl-5-methylphenol), 2,2′-methylenebis(6-tert-butyl-4-methylphenol), 2,5-di(tert-amyl)hydroquinone, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate, and tris(2,4-di-tert-butylphenyl)phosphite.

[0057] Exemplary hindered amine light stabilizers include N,N',N'',N'''-tetrakis(4,6-bis(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)triazin-2-yl)-4,7-diazadecane-1,10-diamine, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, decanedioic acid, 1,10-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)ester decanedioic acid, 1-methyl 10-(1,2,2,6,6-pentamethyl-4-piperidinyl), and bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate.

[0058] Typical amine synergists or coinitiators commonly used with Type II photoinitiators include, but are not limited to, tertiary aliphatic amines such as methyldiethanolamine, dimethylethanolamine, triethanolamine, triethylamine, and N-methylmorpholine; aromatic amines such as amyl paradimethylaminobenzoate, 2-n-butoxyethyl-4-(dimethylamino)benzoate, 2-(dimethylamino)ethyl benzoate, ethyl-4-(dimethylamino)benzoate, and 2-ethylhexyl-4-(dimethylamino)benzoate; and (meth)acrylated amines such as dialkylaminoalkyl(meth)acrylates (e.g., diethylaminoethyl acrylate) or N-morpholinoalkyl-(meth)acrylates (e.g., N-morpholinoethyl-acrylate).

[0059] In certain embodiments, the photocurable composition may include one or more optical brighteners (i.e., optical brightening agents). Optical brighteners, optical brightening agents (OBAs), fluorescent brightening agents (FBAs), or fluorescent whitening agents (FWAs) are compounds that absorb light in the ultraviolet and violet regions of the electromagnetic spectrum (typically 340-370 nm) and re-emit light in the blue region (typically 420-470 nm) by fluorescence. Suitable optical brighteners include, but are not limited to, bisbenzoxazoles; coumarins; stilbenes, including triazine stilbenes and biphenyl stilbenes; diazoles; triazoles; benzoxazolines; combinations thereof; and the like. Fluorescent brighteners are preferred. In some embodiments, the optical brightener acts as a sensitizer. Commercially available optical brighteners include, but are not limited to, Optiblank PL (3V Sigma); Benetex OB, OB Plus, and OB-M1 (Meizo).

[0060] UV blocking agents. Any suitable filler may be used in connection with the various embodiments described herein depending on the desired properties of the part or object being manufactured. Accordingly, the filler may be solid or liquid, organic or inorganic, and reactive and non-reactive rubbers, all examples of which include siloxanes, organic phosphinates, acrylonitrile butadiene rubber; reactive and non-reactive thermoplastics (such as poly(etherimide), maleimide-styrene terpolymer, polyarylate, polysulfone, and polyethersulfone); silicates (such as talc, clay, silica, or mica), glass, carbon nanotubes, graphene, carbon fiber, metals, and cellulose nanocrystals, and combinations thereof.

[0061] Any suitable filler may be used in connection with the various embodiments described herein, depending on the desired properties of the part or object being manufactured. Accordingly, the filler may be solid or liquid, organic or inorganic, and may include reactive and non-reactive rubbers, all of which include siloxanes, organic phosphinates, acrylonitrile-butadiene rubbers; reactive and non-reactive thermoplastics (such as poly(etherimides), maleimide-styrene terpolymers, polyarylates, polysulfones, polyethersulfones, etc.); silicates (such as talc, clay, silica, or mica); glass; carbon nanotubes; graphene; carbon fibers; metals; cellulose nanocrystals; and combinations thereof. The photocurable composition may include one or more polymeric and / or inorganic reinforcing agents. The reinforcing agents may be substantially uniformly dispersed in the polymerization product in the form of particles. The particles may have a diameter of less than 5 μm. Such toughening agents include elastomers, branched polymers, hyperbranched polymers, dendrimers, rubbery polymers, rubbery copolymers, block copolymers, core-shell particles, oxides, or inorganic materials (such as clays, polyhedral oligomeric silsesquioxanes (POSS), carbonaceous materials (e.g., carbon black, carbon nanotubes, carbon nanofibers, and fullerenes), ceramics, and silicon carbide), with or without surface modification or functionalization. Core-shell particle compositions, such as those described in U.S. Patent Application Publication Nos. 2010 / 0280151 and 2007 / 0027233, the entire contents of which are incorporated herein by reference, may also be added as fillers. In some embodiments, the core-shell rubber particles are nanoparticles, i.e., have an average particle size of less than 1,000 nanometers (nm). Typically, the average particle size of core-shell rubber nanoparticles is less than 500 nm, i.e., less than 300 nm, less than 200 nm, less than 100 nm, or less than 50 nm. Typically, such particles are spherical, so the particle size is the diameter, but if the particle is not spherical, the particle size is defined as the longest dimension of the particle.

[0062] Examples of waxes and wax-like additives include microcrystalline wax, beeswax, carnauba wax, paraffin wax, polyethylene glycol wax, candelilla wax, ozokerite wax, olicary wax, microcrystalline wax, amide wax, erucamide wax, polypropylene wax, paraffin wax, polyethylene wax, polytetrafluoroethylene wax, carnauba wax, polyethylene glycol having a molecular weight of more than 1000 daltons, poly(tetramethylene ether) glycol having a molecular weight of more than 650 daltons, etc. The wax may also be a combination of these waxes. The waxes and wax-like additives may have reactive or non-reactive functional groups on them.

[0063] In certain embodiments, the photocurable composition may include one or more plasticizers. Suitable plasticizers include, but are not limited to, phthalates, benzoic acid-based esters, polyketones, diphenates, cyclohexane polycarboxylic acid esters, dialkyl adipates, or mixtures thereof. Some examples include bis(2-ethylhexyl phthalate) (DEHP or DOP), diisononyl phthalate (DINP), dioctyl phthalate (DnOP), diisodecyl phthalate (DIDP), dipropylheptyl phthalate (DPHP), di-2-ethylhexyl terephthalate (DOTP or DEHT), and diisononyl-1,2 cyclohexanedicarboxylate (DIDC, for example, BASF's Hexamol® Dinch®).

[0064] The photocurable composition may have additional ingredients dissolved or dispersed therein, including pigments, dyes, detectable compounds (such as fluorescent, phosphorescent, and radioactive), fillers, light absorbers, dispersants, slip agents, leveling agents, optical brighteners, defoamers, antistatic agents, ultraviolet sensitizers, waxes, plasticizers, amine synergists or coinitiators, or polymerization inhibitors, etc., depending on the particular purpose of the product being made.

[0065] In certain embodiments, the photocurable composition may contain one or more surfactants or dispersants. Surfactants include, but are not limited to, anionic surfactants, nonionic surfactants, cationic surfactants, or amphoteric surfactants. Examples of anionic surfactants include mixed fatty acid sodium soaps and fatty acid sodium salts such as sodium stearate, higher alcohol sodium sulfates, sodium alkyl sulfates, alkylbenzene sulfonic acids, etc. Examples of cationic surfactants and amphoteric surfactants include alkylamines, alkylbetaines, etc. Examples of dispersants include ethyl cellulose, ethylhydroxyethyl cellulose, etc.

[0066] In certain embodiments, the photocurable composition may include one or more slip agents, including, but not limited to, silicones such as polydimethylsiloxane (PDMS), fluoropolymers, alkyl ketal esters, fatty acid amides, etc. Fatty acid amides are generally derived from saturated and / or unsaturated aliphatic fatty acids containing 16 to 22 carbon atoms, including, but not limited to, erucamide, oleamide, stearamide, behenamide, oleyl palmitamide, etc.

[0067] In certain embodiments, the photocurable composition may include one or more leveling agents, including, but not limited to, polyaminoamides and derivatives thereof, polyalkanolamines and derivatives thereof, polyethyleneimines and derivatives thereof, quaternized polyethyleneimines, polyglycines, poly(allylamine), polyanilines, polyureas, polyacrylamides, poly(melamine-co-formaldehyde), reaction products of amines and epichlorohydrin, reaction products of amines, epichlorohydrin, and polyalkylene oxides, reaction products of amines and polyepoxides, polyvinylpyridines, polyvinylimidazoles, polyvinylpyrrolidones, or copolymers thereof, nigrosine, hydrogen halides of pentamethyl-para-rosaniline, hydrogen halides of hexamethyl-para-rosaniline, or compounds containing a functional group of the formula NRS, where R is a substituted alkyl, unsubstituted alkyl, substituted aryl, or unsubstituted aryl. Typically, the alkyl group is (C1-C6) alkyl, preferably (C1-C4) alkyl. Generally, the aryl group includes (C6-C20) aryl, preferably (C6-C10) aryl. Such aryl groups may further include heteroatoms such as sulfur, nitrogen, and oxygen. Preferably, the aryl group is phenyl or naphthyl. Compounds containing a functional group of formula NRS are generally known and generally commercially available, and may be used without further purification.

[0068] The additives are present in an amount of from about 0.01% to about 60%, preferably from about 1% to 25%, more preferably from about 1% to about 10% by weight of the total composition.

[0069] The components are then combined and mixed until they react to prepare a composition. The reacted mixture is applied to a substrate or deposited as a free-standing 3D structure by coating, lithography, and / or printing. Applications include digital light processing, stereolithography, slot-die coating, spray coating, wet coating, screen printing, UV nanoimprint lithography or photo-nanoimprint lithography, step and flash imprint lithography, selective laser sintering, fused deposition modeling, fused filament fabrication, polyjet, inkjet printing, and the like. Those skilled in the art may use solvents, monomers, and rheology modifiers to modify the viscosity of the composition to suit the chosen application method.

[0070] To photocure the photocurable composition, the composition is exposed to radiation in the range of 355 nm to 405 nm of the electromagnetic spectrum. The radiation may be emitted from an LED light source, which may be selected from a laser, multiple lasers, a projector, or multiple projectors. The LED light source may be applied from below or above the reservoir containing the photocurable composition.

[0071] Curing is achieved by exposing the composition to actinic radiation, ultraviolet light, and visible light, which polymerizes and hardens the composition. Single-reaction mechanism energy polymerization uses energy to initiate and drive polymerization via a single reaction mechanism. Irradiation involves exposure to actinic radiation, ultraviolet light, and visible light. Examples include ultraviolet light (100 nm to 405 nm), visible light (405 nm to 700 nm), or electron beams. Examples of suitable light sources include LEDs, laser diodes, laser beams, lamps (e.g., halogen lamps, Xe, Xe-Hg lamps), LED lasers or LED projectors used in additive manufacturing, LCD, LED, or plasma screens, and visible light irradiating mobile or tablet devices. The polymerization is carried out via a single reaction mechanism, such as free radical, cationic, Michael addition, step-growth, or click chemistry. Typically, photocurable compositions in a liquid or viscous state polymerize to form three-dimensional solids.

[0072] Optionally, the formed investment casting pattern may be treated with a solvent or cleaning fluid. The solvent or cleaning fluid may be selected from lower alkyl alcohols, such as isopropanol, or mild surfactants. The solvent or cleaning fluid may be heated to an elevated temperature during use. In this manner, any unreacted material on the surface of the part may become fluid, making it easier to remove by solvation or mechanical agitation, such as ultrasonication.

[0073] Dimensional stability of an investment pattern is defined as 90% of the final part structure being within a certain tolerance or error, for example, less than about 500 μm, e.g., 200 μm, preferably 100 μm, when compared to the original design / CAD model.

[0074] A slurry is formed on the investment pattern, introduced into the outer layer of the pattern, and then cured to form a shell. This can be either drying or curing. The cured investment shell is then heated to a temperature sufficient to soften the investment pattern and remove it from the investment shell. Above a specific temperature, particularly in the range of about 120°C to about 200°C, and more preferably in the range of about 130°C to about 180°C, the investment pattern softens and can be easily removed from the shell. The composition of the investment pattern can be designed by fine-tuning the thermoreversible crosslinker and chain transfer agent to soften at a specific temperature within the range of 120°C to 200°C. In one embodiment, the photocurable composition provides high mechanical strength below 130°C and melts at temperatures above 130°C.

[0075] Without being bound by any particular theory, the addition of a difunctional monomer or oligomer with a balanced Tg imparts strength to the polymer backbone. This resembles an irreversibly crosslinked system of difunctional monomers / oligomers, similar to thermosets, which do not melt but rather burn when heated. The investment casting compositions herein are designed to decrosslink the difunctional monomers / oligomers via a reversible Diels-Alder reaction upon exposure to heat. The combination of the reversible Diels-Alder reaction and a chain transfer reagent that reduces the side chains and the overall molecular weight of the polymer results in the investment casting pattern softening around 130°C. The investment casting compositions described herein are designed to develop mechanical strength below 130°C and become ductile above 130°C. This unique property has led to applications in the pharmaceutical, agricultural, adhesive, and packaging industries.

[0076] Heat allows for the thermoreversibility of the photocurable composition, which has many applications, including investment casting processes. Three-dimensional printing can be used to apply the thermoreversible photocurable composition when rework or removal is required. This composition may be applied in a variety of ways.

[0077] The separated investment shell can be used as a basis for forming an object or product. A second composition is formed on the innermost layer of the investment shell and then cured to essentially assume the shape of the removed pattern. After the second composition has cured, the investment shell can be removed by heat or destroyed to separate it from the object.

[0078] It will be apparent to those skilled in the art that many modifications and variations can be made in this invention without departing from its spirit and scope. The specific embodiments described herein are offered by way of example only, and the invention is limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. [Example]

[0079] A thermoreversible crosslinker was prepared by dissolving 1,1'-(methylenedi-4,1-phenylene)bismaleimide in acryloylmorpholine (ACMO), centrifugal mixing at 2000 RPM for 5 minutes, and adding two equivalents of furfuryl methacrylate. The solution was transferred to a round-bottom flask and mixed at 100 RPM for 8 hours at 60°C, then cooled to 25°C for 24 hours.

[0080] All the ingredients listed in Table 1 were mixed in a container and mixed in an overhead mixer (Cowles blade) at 800 RPM for 2 hours to produce Samples A to D. The resulting liquid resin was mixed in 100 micron layers at 75 mJ / cm per layer. 2 The specimens were loaded into a DLP-based 3D printer configured to print at a dose of 1500 mJ / cm2, and ASTM D638 Type IV specimens were printed. The specimens were post-treated by rinsing with isopropanol alcohol for 2 minutes and then air-drying at 25°C for 30 minutes. Each specimen was exposed to a mercury lamp at 1500 mJ / cm2. 2 (total exposure energy) and then stored at 25°C for 24 hours before testing on an Instron Dual Beam instrument.

[0081] DSC was performed on each specimen according to ASTM E794-06 (temperature ramp rate 5°C / min, N2 purge 50 mL / min, range 25-300°C). Peaks and transitions (if present) were determined, and the results are shown in Table 1. DSC measurements were based on two specimens. One of the two specimen DSC curves for each of Samples A-D is shown in Figure 2.

[0082] [Table 1]

[0083] Example A contains a thermoreversible crosslinker, a MW-controlling additive, a high Tg component, and a low Tg component. As shown in Figure 2A, there are endothermic peaks at 110 and 130 °C, which correspond to the reverse Diels-Alder reaction (thermal decrosslinking). Example A also exhibits additional endothermic transitions at 70 and 100 °C, indicating melting. Example A melted to a liquid above 130 °C. Example B does not contain a MW-controlling additive, and therefore only softens above 130 °C without any signs of melting.

[0084] In Example C, the thermoreversible crosslinker was replaced with a standard crosslinker, a urethane methacrylate oligomer. As shown in the DSC curve, no endothermic transition occurred and the sample remained a thermoset and did not melt or soften above 150°C.

[0085] Example D does not contain any low Tg components. The DSC curves for each exhibited an endothermic peak at 130 °C, corresponding to the reverse Diels-Alder reaction, but the composition did not melt above 150 °C. A gel-like material formed above 130 °C.

Claims

1. A) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value greater than about 25°C; C) a thermoreversible crosslinker having a UV curing function and a thermoreversible covalent bond; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, an irreversible chain transfer agent, an antioxidant, a hindered amine light stabilizer, or a mixture thereof; 1. An investment casting pattern composition comprising:

2. 10. The investment casting pattern composition of claim 1, wherein the monomer A has a functional group selected from methacrylate, acrylate, vinyl ester, vinyl ether, allyl, N-vinyl, vinylamide, acrylamide, vinyl carbonate, acryloyl, vinyl carbamate, maleimide, cyanoacrylate, thiol, or epoxy.

3. 3. The investment casting pattern composition of claim 2, wherein said monomer A has a functional group selected from methacrylate, acrylate, N-vinyl, acrylamide, maleimide, or acryloyl.

4. 2. The investment casting pattern composition of claim 1, wherein the monomer B has a functional group selected from methacrylate, acrylate, vinyl ester, vinyl ether, allyl, N-vinyl, vinylamide, acrylamide, vinyl carbonate, acryloyl, vinyl carbamate, maleimide, cyanoacrylate, thiol, or epoxy.

5. 5. The investment casting pattern composition of claim 4, wherein said monomer B has a functionality selected from narrow methacrylate, acrylate, N-vinyl, acrylamide, maleimide, or acryloyl.

6. The thermoreversible crosslinking agent is a) a bismaleimide or a compound having two or more maleimide groups; b) furfuryl methacrylate or furfuryl arylate; is prepared by reacting 10. The investment casting pattern composition of claim 1, wherein the molar ratio of a to b is from 0.5 to 2 equivalents.

7. 2. The investment casting pattern composition of claim 1, wherein the photoinitiator is a Norrish Type I initiator selected from 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 1-hydroxycyclohexyl-phenyl ketone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO), or ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (TPO-L).

8. 2. The investment casting pattern composition of claim 1, wherein the additive is a chain transfer agent selected from the group consisting of allyl sulfide, allyl phenyl sulfone, ethyl 2-tosyloxyacrylate, ethyl 2-(1-hydroxyperoxyethyl)propenoate, mono-β-allyl sulfone, α-(benzyloxy)styrene, carbon tetrachloride, carbon tetrabromide, bromotrichloromethane, 4-methylbenzenethiol, pentaphenylethane, tert-nonyl mercaptan, 4,4′-thiobisbenzenethiol, N-octyl mercaptan, thioglycolic acid, and mixtures thereof.

9. 10. The investment casting pattern composition of claim 1, wherein the melting point is from about 100°C to about 250°C.

10. A) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value greater than about 25°C; C) Oligomers having two or more furan-maleimide Diels-Alder adducts; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, an irreversible chain transfer agent, an addition-fragmentation chain transfer agent (AFCT), an antioxidant, a hindered amine light stabilizer, or a mixture thereof; A photocurable composition comprising:

11. 11. The photocurable composition of claim 10, wherein said monomer A has functional groups consisting of methacrylate, acrylate, vinyl ester, vinyl ether, allyl, N-vinyl, and mixtures thereof.

12. 11. The photocurable composition of claim 10, wherein said monomer B has functional groups consisting of methacrylate, acrylate, vinyl ester, vinyl ether, allyl, N-vinyl, and mixtures thereof.

13. The oligomer is a) a bismaleimide or a compound having two or more maleimide groups; b) Furfuryl methacrylate or furfuryl arylate is prepared by reacting 11. The photocurable composition according to claim 10, wherein the molar ratio of a to b is 0.5 to 2 equivalents.

14. 11. The photocurable composition of claim 10, wherein the photoinitiator is a Norrish Type I initiator selected from 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 1-hydroxycyclohexyl-phenyl ketone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO), or ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (TPO-L).

15. 11. The photocurable composition of claim 10, wherein the additive is a chain transfer agent selected from the group consisting of allyl sulfide, allyl phenyl sulfone, ethyl 2-tosyloxyacrylate, ethyl 2-(1-hydroxyperoxyethyl)propenoate, mono-β-allyl sulfone, α-(benzyloxy)styrene, carbon tetrachloride, carbon tetrabromide, bromotrichloromethane, 4-methylbenzenethiol, pentaphenylethane, tert-nonyl mercaptan, 4,4′-thiobisbenzenethiol, N-octyl mercaptan, thioglycolic acid, and mixtures thereof.

16. The photocurable composition of claim 10 having a melting point of from about 100°C to about 250°C.

17. The cured photocurable composition of claim 10.

18. 1) a. A) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value greater than about 25°C; C) a thermoreversible crosslinker having a UV curing function and a thermoreversible covalent bond; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, an irreversible chain transfer agent, an antioxidant, a hindered amine light stabilizer, or a mixture thereof; preparing a photocurable composition comprising: b. photocuring the photocurable composition to form a cured three-dimensional pattern having a first side and a second side, the second side being an outermost side; 2) applying a slurry solution onto the second surface of the hardened three-dimensional pattern; 3) drying, curing or solidifying the slurry solution to form a shell on the cured pattern; 4) heating the hardened three-dimensional pattern and the shell to a temperature sufficient to soften the hardened three-dimensional pattern; and 5) separating the hardened three-dimensional pattern from the shell; 1. A method for manufacturing a three-dimensional investment shell, comprising:

19. 20. The method for producing a shell according to claim 18, wherein the temperature in step 4) is from about 130°C to about 250°C.

20. 1) preparing a pattern having a first surface and a second surface, the second surface being the outermost, the pattern being prepared by photocuring a photocurable composition comprising: A) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value greater than about 25°C; C) a thermoreversible crosslinker having a UV curing function and a thermoreversible covalent bond; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, an irreversible chain transfer agent, an antioxidant, a hindered amine light stabilizer, or a mixture thereof; 2) applying a slurry solution to a second surface of the pattern; 3) drying, curing or solidifying the slurry solution to form a shell on the second surface of the pattern; 4) heating the pattern and the shell to a temperature sufficient to soften the pattern; 5) separating the pattern from a shell having a first surface and a second surface, the first surface being the innermost surface; 6) applying a second composition to the first surface of the shell; 7) drying, curing or solidifying the second composition; and 8) removing the shell from the second composition, thereby forming an object; A method of manufacturing an object, comprising:

21. 1) combining and mixing the following ingredients to form a mixture: A) Monomer A having a glass transition temperature value of less than about 25°C; B) Monomer B having a glass transition temperature value greater than about 25°C; C) a thermoreversible crosslinker having a UV curing function and a thermoreversible covalent bond; D) a photoinitiator; and E) an additive selected from the group consisting of a chain transfer agent, an irreversible chain transfer agent, an antioxidant, a hindered amine light stabilizer, or a mixture thereof; 2) applying the mixture onto a substrate or depositing the mixture as a free-standing 3D structure; and 3) photocuring the mixture to harden it into a removable photocurable composition; A method for producing a thermoreversible photocurable composition, comprising:

22. 22. The method for producing a thermoreversible photocurable composition according to claim 21, wherein applying the mixture is by digital light processing, stereolithography, slot die coating, spray coating, wet coating, screen printing, UV nanoimprint lithography or photo nanoimprint lithography, step and flash imprint lithography, selective laser sintering, fused deposition modeling, fused filament fabrication, polyjet, or inkjet printing.

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