Additive manufacturing method for realizing three-dimensional parts having excellent characteristics

Abstract

Provided herein are additive manufacturing methods for achieving three-dimensional parts with superior properties.

Description

Technical Field

[0001] The present disclosure relates to a stereolithography method for realizing three dimensional parts having excellent characteristics.

Background Art

[0002] <Brief Description of Related Art> When an energy polymerizable resin having a single reaction mechanism is cured, its mechanical properties generally deteriorate compared to conventional thermoplastics. The toughness of many engineering thermoplastic materials, such as impact strength, elongation, and tensile strength, is much higher than that of energy polymer materials having a single reaction mechanism. Further, when conventional energy polymerizable resins are formulated to achieve a higher heat deflection temperature (HDT), they exhibit even lower toughness.

[0003] Energy polymer materials, which are attempts to improve the mechanical property performance of a single reaction mechanism, use high molecular weight polyfunctional energy polymerizable oligomers. These oligomers have a low crosslink density when polymerized, but a high overall chain molecular weight. However, due to the high viscosity of high molecular weight oligomers, their use in viscosity-limited applications such as inkjet printing, stereolithography (SLA), digital light processing (DLP), and three-dimensional printing (3DP) is restricted.

[0004] In conventional stereolithography techniques, the construction of three-dimensional parts is performed in a stepwise or layer-by-layer manner. In particular, layer formation is generally performed by solidification of a photocurable resin exposed to visible light or UV light irradiation.

[0005] When a new layer is formed on the top surface of the growing part, after each irradiation step, the part under construction is lowered into a "pool" of resin, a new layer of resin is coated on top of it, and a new irradiation step is performed. The drawback of such "top-down" techniques is that the object growing within the (potentially deep) pool of liquid resin is submerged and it is necessary to reconstruct the exact upper layer of the liquid resin.

[0006] When a new layer is formed at the bottom of the object being grown, after each irradiation step, the object under construction is moved away from the bottom plate of the production well. Such "bottom-up" techniques have the potential to eliminate the need for a deep well in which the object is submerged by instead lifting the object from a relatively shallow well or pool. The viscosity is also a constraint for both of these lamination techniques because fluids with viscosities less than 2000 cPs typically require a consistent layer at the upper or lower interface. Additionally, the bottom-up technique approach is preferred over more rigid materials in order to ensure a consistent layer-by-layer placement and surface finish of the final part. The pot life stability is also an important consideration for all techniques because polymerization that can occur in the absence of energy initiation can result in part defects or solidification of the entire bath. Examples of such polymerization reactions can occur in many of the dual reaction mechanism materials provided by Carbon Inc., such as CE220, CE221, EPU40, EPX81, FP50, RPU60, RPU61, and RPU70.

[0007] An energy-polymerizable resin having a single reaction mechanism is described in U.S. Patent No. 10,239,255, and its mechanical properties are improved through a compounding strategy. The '255 patent claims a free-radical polymerizable liquid. The free-radical polymerizable liquid contains a reactive oligomer, and the reactive oligomer includes at least one (i) polyfunctional methacrylate oligomer and (ii) polyfunctional acrylate oligomer; a reactive monofunctional monomer, and the reactive monofunctional monomer is at least one of (i) a monofunctional N-vinyl monomer, (ii) a monofunctional vinyl ether monomer, (iii) a monofunctional vinyl ester monomer, (iv) a monofunctional vinyl amide monomer, (v) a styrene monomer, (vi) a monofunctional acrylamide monomer, (vii) a monofunctional (meth)acrylate monomer, (viii) a cyanoacrylate monomer, (ix) a monofunctional vinyl carbonate monomer, (x) a monofunctional acryloyl monomer, and (xi) a monofunctional vinyl carbamate monomer. The molar bonding ratio of the reactive ethylenic unsaturated group of the reactive monofunctional species to the reactive ethylenic unsaturated group of the reactive polyfunctional species is at least 10:1. The total weight percentage of the reactive monofunctional species in the calculation of the molar bonding ratio is at least 25% of the polymerizable liquid, and the total weight percentage of the reactive polyfunctional species in the calculation of the molar bonding ratio is at least 25% of the polymerizable liquid. The free-radical polymerizable liquid is an energy-polymerizable liquid that can be cured by a single reaction mechanism to form a photoplastic material.

Summary of the Invention

Problems to be Solved by the Invention

[0008] Nevertheless, in many three-dimensional parts manufactured by, for example, inkjet printing, SLA, DLP, or 3DP, further improvement of physical properties (such as toughness at a high heat deflection temperature) is still desired. So far, these improvements have not been realized yet. Therefore, the need for a method to achieve the required properties in such parts still exists.

Means for Solving the Problems

[0009] <Summary> That need is met herein.

[0010] Generally, that need is met by a process technology that involves the use of a functionalized material that is not fluid at room temperature.

[0011] Provided herein is a method for performing stereolithography using a photocurable composition to form a three-dimensional part. Typically, stereolithography is performed on a build substrate. And the three-dimensional part is created based on data indicating a predetermined pattern. This method includes the following steps: A. Providing a non-fluid photocurable composition in a reservoir such as a hopper, container or vessel; B. Exposing the photocurable composition to conditions favorable for making the photocurable composition fluid; C. Exposing the fluid photocurable composition to radiation in the electromagnetic spectrum appropriate to initiate its polymerization such that a three-dimensional printed part is created according to data indicating a predetermined pattern. including.

[0012] In one embodiment, when polymerized, the photocurable composition has adjustable mechanical properties by varying the energy polymerization conditions by additional exposure to radiation in the electromagnetic spectrum.

DETAILED DESCRIPTION OF THE INVENTION

[0013] <Detailed Description> As described above, provided herein is a method for performing stereolithography using a photocurable composition to form a three-dimensional part. Typically, stereolithography is performed on a build substrate. And the three-dimensional part is created based on data indicating a predetermined pattern. This method includes the following steps: A. Providing a non-fluid photocurable composition in a reservoir; B. exposing the photocurable composition to conditions favorable for rendering the photocurable composition in a fluid state; C. exposing the fluid photocurable composition to radiation in the electromagnetic spectrum suitable for initiating its polymerization such that the three-dimensional printed part is fabricated according to data indicative of a predetermined pattern; comprising.

[0014] The photocurable composition comprises a functionalized component that is solid or non-fluid at room temperature. The solid functional component should have at least one, desirably at least two functional groups selected from (meth)acrylates, α-olefins, N-vinyls, vinylamides, cyanoacrylates, (meth)acrylamides, acryloyls, styrenics, epoxides, thiols, 1,3-dienes, vinyl halides, acrylonitriles, vinyl esters, maleimides, nadimides, itaconimides, vinyl ethers, vinyl carbonates, and vinyl carbamates. Desirably, the functional group is a (meth)acrylate. And desirably, there are at least two (meth)acrylate functional groups.

[0015] In one aspect, the photocurable composition comprises a functionalized component that is solid or non-fluid at room temperature and has a backbone selected from sulfones, styrenes, isocyanurates, cyanate esters, maleimides, nadimides, itaconimides, bicycloalkyls (e.g., adamantyl, fenchyl or norbornyl), biphenyls, novolacs, triazines, carbonates, amides, urethanes, ureas, polyesters, and combinations thereof. The term "backbone" is intended to refer to the chemical moiety to which the functional groups are attached or between which the functional groups are attached.

[0016] For a suitable selection of solid or non - flowing functionalized components at room temperature, commercially available ones include, for example, BR - 571 from Dymax Corporation, Torrington, CT, CN9788 from Sartomer Inc., Exton, PA, many bis - maleimides from Huntsman Corporation, and Compimide MDAB and Compimide 200 from Evonik, etc.

[0017] In some embodiments, the photocurable composition comprises from about 1, 2 or 5 weight percent to 20, 30, 40, 90 or 99 weight percent of a solid or non - flowing functionalized material at room temperature.

[0018] Desirably, the solid functionalized component should be used in an amount of about 90 to about 99 weight percent based on the photocurable composition.

[0019] The photocurable composition comprises a solid or non - flowing functionalized component at room temperature that should have a molecular weight greater than about 400 Mn, desirably greater than about 800 Mn, more desirably greater than about 1200 Mn, as measured in Daltons respectively.

[0020] In one aspect, the photocurable composition comprises a solid or non - flowing functionalized component at room temperature that contains a crystalline structure at a temperature of about 25 °C (usually considered room temperature) or higher.

[0021] For a suitable selection of solid or non - flowing functionalized components in the crystalline structure at room temperature, it includes sulfones, styrenes, isocyanurates, cyanate esters, maleimides, nadimides, itaconamides, bicycloalkyls (e.g., adamantyl, menthyl or norbornyl), biphenyls, novolacs, triazines, carbonates, amides, urethanes, ureas, polyesters, and combinations thereof.

[0022] The photocurable composition contains a functionalized component that is solid or non-fluid at room temperature and, in another aspect, exhibits a solid-to-liquid phase change of from 1°C to 10°C, such as within 5°C, over a period of 20 minutes upon an increase in temperature measured by DSC.

[0023] The photocurable composition should often also contain a photoinitiator. Suitable photoinitiators include triazines, ketones, peroxides, diketones, azides, azo derivatives, disulfide derivatives, disilane derivatives, thiol derivatives, diselenide derivatives, diphenylditelluride derivatives, digermanium derivatives, distannane derivatives, carbon-germanium compounds, carbon-silicon derivatives, sulfur-carbon derivatives, sulfur-silicon derivatives, peresters, Barton ester derivatives, hydroxamic acids and thiohydroxamic acids and esters, organic borates, organometallic compounds, titanocenes, chromium complexes, aluminate complexes, carbon-sulfur or sulfur-sulfur initiator compounds, oximes, aldehydes, acetals, silanes, phosphorus-containing compounds, borane complexes, thioxanthone derivatives, coumarins, anthraquinones, fluorenones, and ferrocenium salts. Particularly desirable photoinitiators include benzophenone, anthraquinone, and fluorenone.

[0024] When used, the photoinitiator should be present in an amount of from about 0.01 weight percent to about 15 weight percent.

[0025] The photocurable composition may contain a thermal initiator but does not require it.

[0026] In step B of the method of the present invention, the photocurable composition should be exposed to a temperature between about 45°C and about 160°C, desirably between about 60°C and about 120°C.

[0027] In step B of the method of the present invention, the photocurable composition should have a vapor pressure of less than about 1 mmHg, desirably less than about 0.1 mmHg, more desirably less than about 0.01 mmHg.

[0028] And in step C of the method of the present invention, the photocurable composition should have a vapor pressure of less than about 1 mmHg, desirably less than about 0.1 mmHg, and more desirably less than about 0.01 mmHg.

[0029] In step B of the method of the present invention, the photocurable composition is maintained in a reservoir that is heated to a temperature of from about 45°C to about 160°C, desirably from about 60°C to about 120°C.

[0030] And in step C of the method of the present invention, the photocurable composition is maintained in a reservoir that is heated to a temperature of the composition of from about 45°C to about 160°C, desirably from about 60°C to about 120°C.

[0031] In step C of the method of the present invention, the photocurable composition should be maintained at a temperature at which the photocurable composition can be fluid. That temperature may be about 30°C to about 120°C higher than room temperature, which is a temperature at which dispensing or printing can be performed. Room temperature is usually about 25°C.

[0032] In step C of the method of the present invention, the photocurable composition is exposed to radiation in the electromagnetic spectrum in the range from 355 nm to 405 nm. That radiation can be emitted from an LED source selected from a laser, a plurality of lasers, a projector or a plurality of projectors. The LED source can be applied from below or above the reservoir containing the photocurable composition.

[0033] Energy polymerization of a single reaction mechanism involves initiating and driving polymerization through one reaction mechanism using energy. Irradiation by exposure to actinic rays, ultraviolet rays, or visible light. Such examples include UV light (100 nm to 405 nm), visible light (405 nm to 700 nm), or an electron beam. Examples of suitable light sources include LEDs, laser diodes, laser beams, lamps (such as halogen lamps, Xe, Xe-Hg lamps, etc.), LED lasers or LED projectors used in additive manufacturing, visible light irradiation LCDs, LED or plasma screens, mobile or tablet devices. Next, this polymerization is carried out by a single reaction mechanism such as, by way of example, free radical, cationic, Michael addition, step-growth, click chemistry, etc.

[0034] The photoplastic material is formed by a single reaction mechanism of the photocurable composition after implementing the method of the present invention. Compared with existing photopolymers, the photoplastic has mechanical properties comparable to those of thermoplastics.

[0035] As in U.S. Patent No. 10,239,255 (Talken), the polymerization of the photocurable composition occurs through a single reaction mechanism. For details, refer to the '255 patent.

[0036] In step C of the method of the present invention, in addition to exposure to radiation in the electromagnetic spectrum, the photocurable composition can be exposed to temperature conditions higher than the high temperature conditions used in step B to make the photocurable composition fluid.

[0037] The three-dimensional part formed in step C of the method of the present invention can have a heat deflection temperature (at 0.455 MPa) at least as high as the high temperature of at least step B or step C.

[0038] The three-dimensional part formed in step C of the method of the present invention should achieve at least about 50% of at least one of its ultimate strength, its ultimate stiffness, and its ultimate heat deflection temperature.

[0039] In some embodiments, the method of the present invention uses a photocurable composition as a chip, pellet, powder, wire, spool, or some other particulate solid form factor.

[0040] In some embodiments, the photocurable composition is exposed to a high temperature between about 45°C and about 160°C within a hopper system to make it in a flowable state.

[0041] In some embodiments, the photocurable composition is continuously exposed to a high temperature through a nozzle, a heated core, a hot end, a heated extruder, or a similar device.

[0042] In some embodiments, the photocurable composition is provided in a physical form factor having a high surface area to volume ratio, such as 0.5:1, to enable rapid heat transfer during Step B.

[0043] In some embodiments, the method of the present invention adds Step D, which includes contacting the three-dimensional part with a solvent or a cleaning liquid. The solvent or the cleaning liquid can be selected from lower alkyl alcohols such as isopropanol, or mild surfactants.

[0044] The solvent or the cleaning liquid used herein can be heated to a high temperature. In this way, the unreacted material on the surface of the part can be made fluid, and the unreacted material can be more easily removed by mechanical agitation such as solvation or sonication.

[0045] In some embodiments, the method of the present invention adds Step E, which includes exposing the three-dimensional part formed in Step C to high temperature conditions. The high temperature conditions here can be at least 160°C. Step E can follow either or both of Step C and Step D.

[0046] In step E of the method of the present invention, the high-temperature condition is a temperature condition higher than the high-temperature condition to which the photocurable composition is exposed in step C. The high-temperature condition should be achieved by inclining from the temperature condition of step C to at least one higher temperature condition at a predetermined rate. The higher temperature condition should be about 45°C to about 160°C higher than that of step C.

[0047] In some embodiments, the method of the present invention further comprises step F of exposing the three-dimensional part formed in step C to radiation in an electromagnetic spectrum having a wavelength different from that of the radiation in the electromagnetic spectrum used in step C. The radiation in step F can be emitted from a light source selected from a laser, a plurality of lasers, a projector or a plurality of projectors, or an LED light source that can be selected from a broadband light source. The radiation in step F can be a second form of radiation in the electromagnetic spectrum, such as gamma-ray irradiation, electron beam or microwave irradiation.

[0048] After step E of the method of the present invention, the formed three-dimensional part should achieve at least about 100% of at least one of its ultimate strength, its ultimate rigidity, and its ultimate heat deflection temperature.

[0049] In fact, in some embodiments, the three-dimensional part formed after step E exhibits substantially uniform strength, rigidity, and heat deflection temperature throughout its volume, regardless of where the measurement is taken on the part, its size, shape, internal complexity, or surface.

[0050] The three-dimensional part formed after step E may exhibit a tensile elongation >= yield strength of the three-dimensional part, with a tensile elongation of at least about 6%, preferably at least about 10%, and a heat deflection temperature (at 0.455 MPa) exceeding 100°C, preferably exceeding 120°C, more preferably exceeding 160°C.

[0051] The photocurable composition can reach predetermined physical or mechanical properties regardless of the presence or absence of exposure to high temperature conditions. Such heat exposure can be achieved by active heating (e.g., in an oven such as an electric, gas, or solar heat oven) or passive heating (e.g., at ambient temperature). Active heating is generally faster than passive heating and is preferred in some embodiments, but passive heating - for example, maintaining the intermediate at ambient temperature for a sufficient time to effect further polymerization - is preferred in some embodiments.

[0052] The method of the present invention enables the formation of three-dimensional parts having dimensional stability after performing some or all of the post-treatment steps (i.e., steps D, E, and / or F). This means having 90% of the final part structure within the tolerance or error, such as an inaccuracy in dimensions of less than about 500 μm, e.g., 200 μm, desirably 100 μm, when compared to the original design / CAD model or when compared to the part after step C.

[0053] Depending on the properties desired for the part or object being manufactured, any suitable filler can be used in connection with the various embodiments described herein. Thus, the filler can be solid or liquid, organic or inorganic, and can be reactive and non-reactive rubbers. All of these examples include siloxanes, organic phosphates, acrylonitrile-butadiene rubber, reactive and non-reactive thermoplastics (poly(etherimide), maleimide-styrene terpolymer, polyarylate, polysulfone, polyethersulfone, inorganic fillers such as silicates (talc, clay, silica, mica, etc.), glass, carbon nanotubes, graphene, carbon fibers, metals, etc., and cellulose nanocrystals and combinations thereof.

[0054] Polymers and / or inorganic reinforcing agents of 1 or more can be included in the photocurable composition. The reinforcing agent may be uniformly dispersed in particulate form in the polymerization product. The particles may have a diameter of less than 5 microns (μm). Such reinforcing agents include elastomers, branched polymers, highly branched polymers, dendrimers, rubbery polymers, rubbery copolymers, block copolymers, core-shell particles, oxides or inorganic materials, such as clay, polyhedral oligomeric silsesquioxane (POSS), carbonaceous materials (e.g., carbon black, carbon nanotubes, carbon nanofibers and fullerenes), ceramics and silicon carbide, etc., and the surface may or may not be modified or functionalized. Examples of block copolymers include the copolymers described in U.S. Patent No. 6,894,113, the entire contents of which are incorporated herein by reference, and also NANOSTRENGTH SBM (polystyrene-polybutadiene-polymethacrylate) and AMA (polymethacrylate-polybutyl acrylate-polymethacrylate), both of which are manufactured by Arkema. Other suitable block copolymers include FORTEGRA and the amphiphilic block copolymers described in U.S. Patent No. 7,820,760, the entire contents of which are incorporated herein by reference. Known core-shell particles include, for example, the core-shell (dendrimer) particles described in U.S. Patent Application Publication No. 2010 / 0280151. For example, an amine-branched polymer in which a shell is grafted onto a core polymer obtained by polymerizing a polymerizable monomer containing unsaturated carbon-carbon bond core-shell rubber particles described in European Patent Application Publication No. 1632533 and European Patent Application Publication No. 2123711, the entire contents of which are incorporated herein by reference; a polymer core obtained by polymerizing a polymerizable monomer such as butadiene, styrene, other unsaturated carbon-carbon bond monomers, or combinations thereof, and particles having a polymer shell that is miscible with epoxy, typically polymethyl methacrylate, polyglycidyl methacrylate, polyacrylonitrile, or similar polymers further described below, such as the KaneAce MX product series which is a particle / epoxy blend.In the present invention, suitable block copolymers include JSR SX series, which is carboxylated polystyrene / polyvinylbenzene manufactured by JSR Corporation; KUREHA PARALOID EXL-2655, which is a butadiene alkyl methacrylate styrene copolymer (manufactured by Kureha Chemical Industry Co., Ltd.); STAFILOID AC-3355 and TR-2122, which are acrylate methacrylate copolymers (both manufactured by Takeda Pharmaceutical Company Limited); and PARALOID EXL-2611 and EXL-3387, which are butyl acrylate methyl methacrylate copolymers (both manufactured by Dow Chemical). Examples of suitable oxide particles include NANOPOX manufactured by Nanoresins AG. This is a masterbatch of functionalized silica nanoparticles and epoxy.

[0055] Core-shell rubber is a particulate material (particle) having a rubbery core. Such materials are known and are described in US Patent Application Publication No. 2015 / 0184039, US Patent Application Publication No. 2015 / 0240113, and US Patents No. 6,861,475, 7,625,977, 7,642,316, 8,088,245, etc., the entire contents of which are incorporated herein by reference.

[0056] In some embodiments, the core-shell rubber particles are nanoparticles (i.e., those having an average particle size of less than 1000 nanometers (nm)). Generally, the average particle size of the core-shell rubber nanoparticles is less than 500 nm, for example less than 300 nm, less than 200 nm, less than 100 nm, or even less than 50 nm. Typically, since such particles are spherical, the particle size is the diameter. However, when the particles are not spherical, the particle size is defined as the longest dimension of the particle.

[0057] In some embodiments, the rubbery core may have a Tg of less than -25°C, more preferably less than -50°C, even more preferably less than -70°C. The Tg of the rubbery core may also be significantly lower than -100°C. The core-shell rubber also has at least one shell portion having a Tg of at least 50°C. "Core" means the interior of the core-shell rubber. The core may form the center of the core-shell particles, or the inner shell or region of the core-shell rubber. The shell is a part of the core-shell rubber that is outside the rubbery core. The shell portion(s) typically form the outermost part of the core-shell rubber particles. The shell material may be grafted or crosslinked to the core. The rubber core may constitute 50 to 95 wt% or 60 to 90 wt% of the total amount of the core-shell rubber particles.

[0058] The core of the core-shell rubber may be a polymer or copolymer of a conjugated diene such as butadiene, or a lower alkyl acrylate such as n-butyl-, ethyl-, isobutyl- or 2-ethylhexyl acrylate. The core polymer may further contain up to 20 wt% of other copolymerized mono-unsaturated monomers such as styrene, vinyl acetate, vinyl chloride, methyl methacrylate. The core polymer may be crosslinked. The core polymer may contain up to 5% of a copolymerized graft-bond monomer having two or more heterogeneous reactive unsaturated sites (wherein at least one reactive site is non-conjugated), such as diallyl maleate, monoallyl fumarate, allyl methacrylate.

[0059] The core polymer may be a silicone rubber. This material often has a glass transition point of less than -100°C. Examples of core-shell rubbers having a silicone rubber core include those commercially available under the trade name GENIOPERL from Wacker Chemie, Munich, Germany.

[0060] A shell polymer that can be chemically grafted or crosslinked to a rubbery core can be polymerized from at least one lower alkyl methacrylate such as methyl methacrylate, ethyl methacrylate or t-butyl methacrylate. A homopolymer of such a methacrylate monomer may be used. Further, up to 40% by weight of the shell polymer may be formed from other monovinylidene monomers such as styrene, vinyl acetate, vinyl chloride, methyl acrylate, ethyl acrylate, butyl acrylate. The molecular weight of the shell polymer to be grafted may be from 20,000 to 500,000.

[0061] One suitable type of core-shell rubber is one having a reactive group in the shell polymer that can react with an epoxy resin or an epoxy resin curing agent. Glycidyl groups are suitable. Glycidyl groups are provided by monomers such as glycidyl methacrylate.

[0062] As an example of a suitable core-shell rubber, there is one of the type described in U.S. Patent Application Publication No. 2007 / 0027233, the entire contents of which are incorporated herein by reference. As described herein, core-shell rubber particles are in most cases a crosslinked rubber core that is a copolymer of crosslinked butadiene, and a shell that is preferably a copolymer of styrene, methyl methacrylate, glycidyl methacrylate, and optionally acrylonitrile. The core-shell rubber is preferably dispersed in a polymer or an epoxy resin as described in the literature. Suitable core-shell rubbers include, but are not limited to, those sold under the name Kane Ace by Kaneka Corporation, such as products of the Kane Ace 15 and 120 series, such as Kane Ace MX120, Kane Ace MX153, Kane Ace MX154, Kane Ace MX156, Kane Ace MX170, and Kane Ace MX257, and Kane Ace MX120 core-shell rubber dispersions, and mixtures thereof.

[0063] Resins suitable for the photocurable composition include photocurable silicones. UV curable silicone rubbers such as SILIOPREN® UV curable silicone rubber and LOCTITE curable silicone adhesive sealants. Applications include optical instruments, medical and surgical instruments, exterior lighting and enclosures, electrical connectors / sensors, optical fibers, gaskets, and molds.

[0064] Biodegradable resins for photocurable compositions are particularly important for implantable devices or temporary function applications for delivering drugs such as biodegradable screws and stents (U.S. Pat. Nos. 7,919,162 and 6,932,930, the entire contents of which are incorporated herein by reference). A biodegradable copolymer of lactic acid and glycolic acid (PLGA) is dissolved in PEG di(meth)acrylate to obtain a transparent resin suitable for use. Polycaprolactone and PLGA oligomers can be functionalized with acrylic or methacrylic groups to make effective resins in use.

[0065] Another resin suitable for the photocurable composition is a photocurable polyurethane (such as a polyurea, and a copolymer of a polyurethane and a polyurea (e.g., poly(urethane-urea))). A photocurable polyurethane / polyurea composition containing (1) a polyurethane based on an aliphatic diisocyanate, poly(hexamethylene isophthalate glycol) and optionally 1,4-butanediol, (2) a polyfunctional acrylate ester, (3) a photoinitiator, and (4) an antioxidant can be prepared to be a hard, wear-resistant, stain-resistant material (U.S. Pat. No. 4,337,130, the entire contents of which are incorporated herein by reference). A photocurable thermoplastic polyurethane elastomer incorporates a photoreactive diacetylene diol as a chain extender.

[0066] The photocurable composition may have additional components solubilized or dispersed therein, such as pigments, dyes, contrast compounds (e.g., fluorescent, phosphorescent, and radioactive), fillers, light absorbers, or polymerization inhibitors, depending on the specific purpose of the product to be manufactured.

[0067] In some embodiments, for example, in order to promote the reaction of double bonds that may remain unreacted during heat and / or microwave irradiation, an organic peroxide can be included in an energy-polymerizable liquid or resin of a single reaction mechanism. Such an organic peroxide can be included in the resin or polymerizable liquid in any suitable amount, such as 0.001 or 0.01 or 0.1 wt% to 1, 2 or 3 wt%. Suitable organic peroxides include, but are not limited to, for example, 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (e.g., LUPEROX 101), dilauroyl peroxide (e.g., LUPEROX LP), benzoyl peroxide (e.g., LUPEROX A98), bis(tert-butyldioxyisopropyl)benzene (e.g., VulCUP R). Such organic peroxides are available from various suppliers such as Arkema Inc, but are not limited thereto.

[0068] It will be apparent to those skilled in the art that the methods of the present invention are useful in a wide range of additive manufacturing techniques including jet fusion and inkjet methods.

[0069] The photocurable composition can be used in bottom-up additive manufacturing techniques such as, for example, the continuous liquid interface printing technique described in the '255 patent, and other additive manufacturing techniques described herein.

[0070] The three-dimensional objects produced by the methods and processes of the present invention can be end products, finished products or substantially finished products, or intermediate products that are subjected to further manufacturing processes such as surface treatment, laser cutting, electrical discharge machining, etc. Intermediate products include products that can be further additively manufactured using the same or different apparatuses. For example, in order to halt one region of an end product, or simply because a particular region or "build" of the end product is more vulnerable than others, a fault line or score line can be intentionally introduced into the ongoing "build" by disturbing and then restoring the slope of the polymerization region.

[0071] A number of different products, such as large-scale models or prototypes, small custom-made products, miniature or microminiature products or devices, can be manufactured by the method and apparatus of the present invention. For example, hearing aids, stents, drug delivery depots, functional structures, fiber and rod such as microneedle arrays, waveguides, and medical devices and implantable medical devices such as micro mechanical devices and microfluidic devices.

[0072] As further described below, in some embodiments, the manufactured article has at least one, or a plurality of holes or grooves formed therein.

[0073] Manufactured articles having a variety of different properties can be manufactured by the processes described herein. In some embodiments the manufactured article is rigid, and in some other embodiments the manufactured article is flexible and elastic. In some embodiments, the manufactured article is solid. In other embodiments, the manufactured article is a gel such as a hydrogel. In some embodiments, the manufactured article has shape memory (i.e., it generally returns to its previous shape after deformation unless deformed beyond the structural break point). In some embodiments, the manufactured article is a single entity (i.e., formed from one single reaction mechanism energy polymerizable liquid). In some embodiments, the manufactured article is a composite (i.e., formed from two or more different single reaction mechanism energy polymerizable liquids). The particular properties are determined by factors such as the selection of the single reaction mechanism energy polymerizable liquid used.

[0074] In some embodiments, the manufactured product or article has at least one protrusion (or "projection"), such as a crosslinking element between two supports or a cantilever element protruding from one substantially vertical support. The problem that a fault line or cleavage line is formed between layers when a substantial time interval occurs before each layer is polymerized and substantially completed and the next pattern is exposed is significantly reduced by the unidirectional and continuous nature of some embodiments of this process. Thus, in some embodiments, this method is particularly advantageous for reducing or eliminating the number of support structures for such protrusions manufactured simultaneously with the article.

[0075] In some embodiments, the method of the present invention for performing stereolithography using a photocurable composition to form three-dimensional parts having improved physical properties comprises the following steps when the three-dimensional printed part is made according to data indicating a predetermined pattern; providing a non-flowable photocurable composition to a reservoir, subjecting the photocurable composition to conditions favorable for making it in a flowable state, exposing the flowable photocurable composition to radiation in the electromagnetic spectrum appropriate for initiating its polymerization so that a three-dimensional printed part is made according to data indicating a predetermined pattern, and subjecting the three-dimensional part formed in step C to high temperature conditions.

[0076] The physical or structural properties of the three-dimensional part can be selected together with the properties of the photocurable composition from which the three-dimensional printed part is formed to provide a wide range of properties to the three-dimensional printed part. Using the method of the present invention, complex shapes with desired material properties can be formed to form a wide range of three-dimensional parts.

[0077] In some embodiments, the three-dimensional printed part may be rigid, for example, having a Young's modulus (MPa) in the range of about 800 to 4500 or any range subsumed therein, a tensile strength (MPa) in the range of about 30 to 250 or any range subsumed therein, an elongation at break (%) in the range of about 1 to 100 or any range subsumed therein, and / or an IZOD impact strength according to a notched shape in the range of 10 to 200 J / m or any range subsumed therein. Examples of such rigid three-dimensional parts include fasteners; electronic device housings; gears, propellers, and impellers; wheels, machinery housings; tools, and other rigid three-dimensional printed parts.

[0078] In some embodiments, the three-dimensional printed part may be semi-rigid, for example, having a Young's modulus (MPa) in the range of about 300 to 3500 or any range subsumed therein, a tensile strength (MPa) in the range of about 20 to 90 or any range subsumed therein, an elongation at break (%) in the range of about 20 to 300 or 600 or any range subsumed therein, and / or an IZOD impact strength according to a notched shape in the range of about 30 to 400 J / m or any range subsumed therein. Examples of such semi-rigid three-dimensional printed parts include structural elements; hinges such as living hinges; boat and ship hulls and decks; wheels; bottles, flasks, and other containers; pipes, liquid tubes, and connectors, and other semi-rigid three-dimensional printed parts.

[0079] In some embodiments, the three-dimensional printed part may be an elastomer, for example, having a Young's modulus (MPa) in the range of about 0.25 to 300 or any range subsumed therein, a tensile strength (MPa) in the range of about 0.5 to 30 or any range subsumed therein, an elongation at break (%) in the range of about 50 to 1500 or any range subsumed therein, and / or a tear strength in the range of about 10 to 200 kN / m or any range subsumed therein. Examples of such elastomeric three-dimensional printed parts include shoe soles, heels, insoles, and midsoles.

[0080] The production of the part may be stopped or interrupted one or more times to change the photocurable composition. The three-dimensional part produced by the method of the present invention may include a plurality of photocurable compositions having the ability to achieve different tensile strengths when cured. Although a fault line or fault plane may be formed in the intermediate due to the interruption, if the photocurable composition is reactive with the first one in its second polymerizable material, then, during the second polymerization, two different segments of the intermediate cross-react (e.g., by heat or microwave irradiation) and covalently bond to each other. Thus, the part can be formed by the method of the present invention while being a single product having a plurality of distinct segments with different tensile properties, while the different segments are covalently bonded to each other. In some embodiments, the three-dimensional part can be formed from a plurality of regions having different materials and properties. For example, the three-dimensional part is formed from one or more regions formed from a first material or a first group of one or more materials having a tensile strength (MPa) in the range of about 30 to 100 or any range subsumed herein, and / or a second material or a second group of one or more materials having a tensile strength (MPa) in the range of about 20 to 70 or any range subsumed herein, and / or a third material or a third group of one or more materials having a tensile strength (MPa) in the range of about 0.5 to 30 or any range subsumed herein, or any combination thereof. For example, the three-dimensional part may have 1 to 10 or more (or any range subsumed herein) different regions having various tensile strengths selected from any of the above materials and tensile strengths. For example, a hinge may be formed, and by sequentially changing the energy-polymerizable liquid of a single reaction mechanism during the formation of the three-dimensional intermediate, the hinge may include a rigid segment, a second elastic segment bonded thereto, and a third rigid segment bonded thereto. A shock absorber or vibration damper may be formed in a similar manner, and the second segment may be either elastic or semi-rigid. A single rigid funnel and a flexible hose assembly can be formed in a similar manner.

[0081] In some embodiments, a photocurable composition comprising an energy-polymerizable resin of one or more single reaction mechanisms can be used to adjust mechanical properties within the same photoplastic material (or parts made therefrom). This can be achieved by changing the energy polymerization of the photoplastic material, and the reaction activity or reaction mechanism of the system can be changed. For example, by changing light irradiation, light energy, light wavelength, or using an electron beam, the polymerization reaction mechanism and polymerization reaction rate can be changed. This is due to different polymerizable functional groups contained in the resin and their reactivity or non-reactivity with the same or different functional groups to some extent, and these can change the molecular weight and network of the final polymer. This also results to some extent from the same type of initiation that allows all functional groups in the photoplastic material to be polymerized.

[0082] In some embodiments, the three-dimensional parts formed by the method of the present invention meet the UL94 rating of V-1 or V-0. And in some embodiments, the three-dimensional parts formed by the method of the present invention meet the FST (AITM2) of the published Airbus Standard.

[0083] Furthermore, various polymer networks, molecular weights, liquid-solid, solid-solid solubilities, or phase separations can be adjusted and controlled by the above process parameters. Therefore, it is possible to greatly change the mechanical properties of one resin in either pixel units in a film or voxel units in a part. Specifically, in additive manufacturing, VAT polymerization generally occurs by a laser, projector, or screen light source. These and each light source of the next generation can be controlled to emit a lower wattage or lower energy in pixel units. Therefore, three-dimensional control of voxel polymerization is possible, and an object with various mechanical properties in three-dimensional space can be fabricated.

[0084] The present invention is preferably implemented by stereolithography, material jetting, or inkjet printing, but in some embodiments, other methods and apparatuses for bottom-up or top-down three-dimensional manufacturing, such as layer-by-layer manufacturing, may be used. Such methods and apparatuses include, but are not limited to, for example, U.S. Patent No. 5,236,637, U.S. Patent No. 5,391,072, 5,529,473, U.S. Patent No. 7,438,846, U.S. Patent No. 7,892,474, U.S. Patent No. 8,110,135, U.S. Patent Application Publication Nos. 2013 / 0292862 and 2013 / 029521, and International Publication WO2015 / 164234, the entire contents of each of which are incorporated herein by reference.

Claims

**Claim 1** A method of performing additive manufacturing using a photocurable composition to form a three-dimensional part, wherein the three-dimensional part is produced according to data representing a predetermined pattern, the method comprising the steps of: A. providing a non-flowable photocurable composition to a reservoir; B. exposing the photocurable composition to conditions that render the photocurable composition flowable; C. exposing the flowable photocurable composition to radiation in the electromagnetic spectrum suitable for initiating its polymerization so that a three-dimensional printed part is produced according to data representing a predetermined pattern. The method is characterized in that the photocurable composition comprises a solid functionalized component, in step B, the photocurable composition is exposed to a temperature between 45 °C and 160 °C, and in step C, the photocurable composition is exposed to a temperature between 45 °C and 160 °C. **Claim 2** The method according to claim 1, wherein in step B, the photocurable composition is exposed to a temperature between 60 °C and 120 °C. **Claim 3** The method according to claim 1, wherein in step B, the photocurable composition has a vapor pressure of less than 1 mmHg. **Claim 4** The method according to claim 1, wherein in step B, the photocurable composition has a vapor pressure of less than 0.1 mmHg. **Claim 5** The method according to claim 1, wherein in step B, the photocurable composition has a vapor pressure of less than 0.01 mmHg. **Claim 6** The method according to claim 1, wherein in step C, the photocurable composition has a vapor pressure of less than 1 mmHg. **Claim 7** The method according to claim 1, wherein in step C, the photocurable composition has a vapor pressure of less than 0.1 mmHg. **Claim 8** The method according to claim 1, wherein in step C, the photocurable composition has a vapor pressure of less than 0.01 mmHg. **Claim 9** The method according to claim 1, wherein in step B, the photocurable composition is maintained in a reservoir heated to a temperature between 45 °C and 160 °C. **Claim 10** The method according to claim 1, wherein in step B, the photocurable composition is maintained in a reservoir heated to a temperature between 60 °C and 120 °C. **Claim 11** The method according to claim 1, wherein in step C, the photocurable composition is exposed to a temperature between 60 °C and 120 °C. **Claim 12** The method according to claim 1, wherein in step C, the photocurable composition is maintained at a temperature at which the photocurable composition is flowable. **Claim 13** The method according to claim 1, wherein in step B, the photocurable composition is dispensed at a temperature 30 °C to 120 °C higher than room temperature.

14. The method according to claim 1, wherein in step C, the photocurable composition is printed at a temperature 30 °C to 120 °C higher than room temperature.

15. The method according to claim 1, wherein in step C, the photocurable composition is exposed to radiation in the electromagnetic spectrum in the range of 355 nm to 405 nm.

16. The method according to claim 1, wherein in step C, the photocurable composition is exposed to radiation in the electromagnetic spectrum emitted from an LED source.

17. The method according to claim 1, wherein in step C, the photocurable composition is exposed to radiation in the electromagnetic spectrum emitted from an LED source selected from a laser, a plurality of lasers, a projector, or a plurality of projectors.

18. The method according to claim 1, wherein in step C, the photocurable composition is exposed to radiation in the electromagnetic spectrum emitted from an LED source applied from below a reservoir containing the photocurable composition.

19. The method according to claim 1, wherein in step C, the photocurable composition is exposed to radiation in the electromagnetic spectrum emitted from an LED source applied from above a reservoir containing the photocurable composition.

20. The method according to claim 1, wherein in step C, the polymerization of the photocurable composition occurs via a single reaction mechanism.

21. The method according to claim 1, wherein the solid functionalized component has at least one functional group selected from (meth)acrylate, α-olefin, N-vinyl, vinylamide, cyanoacrylate, (meth)acrylamide, acryloyl, styrene, epoxide, thiol, 1,3-diene, vinyl halide, acrylonitrile, vinyl ester, maleimide, nadimide, itaconimide, vinyl ether, vinyl carbonate, and vinyl carbamate.

22. The method according to claim 1, wherein the solid functionalized component has a molecular weight greater than 400 Daltons.

23. The method according to claim 1, wherein the solid functionalized component has a molecular weight greater than 800 Daltons.

24. The method according to claim 1, wherein the solid functionalized component has a molecular weight greater than 1200 Daltons.

25. The method according to claim 1, wherein the solid functionalized component contains a crystal structure at a temperature of 25 °C or higher.

26. The method according to claim 1, wherein in step A, the photocurable composition containing the solid functionalized component exhibits a phase change from solid to liquid within a temperature rise of 5 °C measured over 20 minutes by DSC.

27. The method according to claim 1, wherein in step A, the photocurable composition contains a solid functionalized component having a skeleton selected from sulfone, styrene, isocyanurate, cyanate ester, maleimide, nadimide, itaconamide, adamantyl, biphenyl, novolak, norbornyl, triazine, carbonate, amide, urethane, urea, polyester, and combinations thereof.

28. The method according to claim 1, wherein in step A, the photocurable composition contains a photoinitiator.

29. The method according to claim 1, wherein in step A, the photocurable composition contains a solid functionalized component to which a thermal initiator has not been added.

30. The method according to claim 1, wherein in addition to exposure to radiation in the electromagnetic spectrum, in step C, the photocurable composition is exposed to temperature conditions higher than the temperature conditions used in step B to make the photocurable composition fluid.

31. Step D, D. Contacting the three-dimensional part with a solvent or a cleaning liquid, The method according to claim 1, further comprising.

32. Step E, E. Exposing the three-dimensional part formed in step C to temperature conditions higher than those to which the photocurable composition was exposed in step B. The method according to claim 1, further comprising.

33. Step E, E. Exposing the three-dimensional part formed in step C to temperature conditions higher than those to which the photocurable composition was exposed in step B. The method according to claim 31, further comprising.

34. The method according to claim 32, wherein the temperature conditions in step E are achieved by ramping at a predetermined rate from the temperature conditions of step B to at least one higher temperature condition.

35. The method according to claim 32, wherein the temperature conditions in step E are at least 160 °C.

36. The method according to claim 32, wherein in step E, the polymerization of the photocurable composition occurs via a single reaction mechanism.

37. Step F, F. Exposing the three-dimensional part formed in step C to radiation in the electromagnetic spectrum having a wavelength different from that of the radiation in the electromagnetic spectrum used in step C. The method according to claim 1, further comprising.

38. The method according to claim 37, wherein in step F, the three-dimensional part is exposed to radiation in the electromagnetic spectrum emitted from a light source selected from an LED light source or a broadband light source.

39. The method according to claim 37, wherein in step F, the three-dimensional part is exposed to a second form of radiation in the electromagnetic spectrum.

40. The method according to claim 37, wherein in step F, the three-dimensional part is exposed to a second form of radiation in the electromagnetic spectrum selected from gamma ray irradiation, electron beam or microwave irradiation.

41. The method according to claim 32, wherein the three-dimensional part formed after step C achieves at least 50% of at least one of its ultimate strength, its ultimate stiffness, and its ultimate thermal deflection temperature.

42. The method according to claim 41, wherein the three-dimensional part formed after step E achieves 100% of at least one of its ultimate strength, its ultimate stiffness, and its ultimate thermal deflection temperature.

43. The method according to claim 42, wherein the three-dimensional part formed after step E exhibits a tensile elongation of the three-dimensional part >= yield strength.

44. The method according to claim 42, wherein the three-dimensional part formed after step E exhibits a tensile elongation of at least 6%.

45. The method according to claim 42, wherein the three-dimensional part formed after step E exhibits a tensile elongation of at least 10%.

46. The method according to claim 42, wherein the three-dimensional part formed after step E exhibits a thermal deflection temperature (at 0.455 MPa) exceeding 100 °C.

47. The method according to claim 42, wherein the three-dimensional part formed after step E exhibits a thermal deflection temperature (at 0.455 MPa) exceeding 120 °C.

48. The method according to claim 42, wherein the three-dimensional part formed after step E exhibits a thermal deflection temperature (at 0.455 MPa) exceeding 160 °C.

49. The method according to claim 1, wherein the photocurable composition is provided as a chip, pellet, powder, wire, spool, or other particulate solid form factor.

50. The method according to claim 1, wherein the photocurable composition is exposed to a temperature between 45 °C and 160 °C in a hopper system to make it in a flowable state.

51. The method according to claim 1, wherein the photocurable composition is continuously exposed to the temperature of step B via a nozzle, a heated core, a hot end, a heated extruder or a similar device.

52. The method according to claim 1, wherein the photocurable composition is provided with a physical shape factor having a surface area to volume ratio exceeding 0.5:

1.

53. A method of performing additive manufacturing using a photocurable composition to form a three-dimensional part having excellent physical properties, wherein the three-dimensional part is produced based on data indicating a predetermined pattern, and the following steps: A. Providing a photocurable composition in a non-flowing state to a reservoir; B. Exposing the photocurable composition to conditions that render the photocurable composition in a fluid state; C. Exposing the fluid photocurable composition to radiation in the electromagnetic spectrum suitable to initiate its polymerization such that a three-dimensional printed part is produced according to data indicating a predetermined pattern; D. Exposing the three-dimensional part formed in step C to higher temperature conditions than those to which the photocurable composition is exposed in step B. The method comprising: In step B, the photocurable composition is exposed to a temperature between 45°C and 160°C; In step C, the photocurable composition is exposed to a temperature between 45°C and 160°C.