METHOD OF TREATING ADDITIVE MANUFACTURING
OBJECTS WITH A COMPOUND OF INTEREST
Field of the Invention
The present invention concerns methods for additive manufacturing, particularly for stereolithography techniques such as continuous liquid interface production.
Background of the Invention
A group of additive manufacturing techniques sometimes referred to as "stereolithography" create a three-dimensional object by the sequential polymerization of a light polymerizable resin. Such techniques may be "bottom-up" techniques, where light is projected into the resin onto the bottom of the growing object through a light transmissive window, or "top down" techniques, where light is projected onto the resin on top of the growing object, which is then immersed downward into the pool of resin.
The recent introduction of a more rapid stereolithography technique known as continuous liquid interface production (CLIP), coupled with the introduction of "dual cure" resins for additive manufacturing, has expanded the usefulness of stereolithography from prototyping to manufacturing. See, e.g., US Patent Nos. 9,211,678, 9,205,601, and 9,216,546 to DeSimone et al.; and also J. Tumbleston, D. Shirvanyants, N. Ermoshkin et al., Continuous liquid interface production of 3D Objects, Science 347, 1349-1352 (2015); see also Rolland et al., US Patent Nos. 9,676,963, 9,453,142 and 9,598,606.
Some additives that may be desirable to include in polymeric objects may, however, be deleterious to steps such as the light polymerization in the additive manufacturing process. Accordingly, new approaches to additive manufacturing are needed.
Summary of the Invention
A first aspect of the invention is a method of making an object from a dual cure resin by additive manufacturing, which object is at least partially impregnated with one or more additives, the method comprising the steps of:
(a) producing a green intermediate object from the dual cure resin by additive manufacturing; (b) optionally cleaning the object ( e.g ., by washing);
(c) further curing the object (e.g., by heating, microwave irradiating, or a combination thereof); and then
(d) at least partially immersing the object in a solvent containing the additive under conditions (e.g., for a time and at a temperature and pressure) sufficient to at least partially impregnate the object with the additive.
Examples of suitable additives include, but are not limited to, ultraviolet light stabilizers or absorbing compounds, colorants, flame retardants, heat stabilizers, antioxidant agents, antistatic agents, radiation stabilizers, or a combination thereof.
The present invention is useful for the production of a variety of objects, including but not limited to midsoles, shock absorbers, cushions, electronic device protective housings such as cell phone housings, and the like.
In some embodiments, the object is flexible or elastic (for which articles at least partial impregnation of the additive therein, rather than simply a surface coating which could flake off upon bending or stretching, is particularly advantageous).
In some embodiments, the producing step is carried out by top-down or bottom-up stereolithography (for example, continuous liquid interface production).
In some embodiments, the resin comprises a polyurethane, polyurea, epoxy, silicone, or cyanate ester resin, or combination thereof.
A further aspect of the in object produced by a method as described above, or below.
Brief Description of the Drawings
FIG. 1 is a photograph of a finished object with open lattice structures produced by dual cure continuous liquid interface production (CLIP) that was immersed in an impregnation solution (rhodamine pigment in isopropanol) at ambient temperature (room temperature, or approximately 25 degrees Celsius), for six hours. As shown in the photograph, the immersed portion was strongly colored by the rhodamine pigment.
FIG. 2 is a drawing representing a cross-section of a portion of the open lattice structure before (left side) and after the impregnation (right side). Upon cutting into the lattice, the dye was seen to have impregnated below the surface of the object, partially into the polymer lattice structures themselves, as schematically illustrated. Detailed Description of Illustrative Embodiments
The present invention is now described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.
As used herein, the term "and/or" includes any and all possible combinations of one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative ("or").
1. POLYMERIZABLE LIQUIDS (RESINS).
Numerous resins for use in additive manufacturing are known and can be used in carrying out the present invention. See, e.g., US Patent No. 9,205,601 to DeSimone et al.
In some embodiments, the resin is a dual cure resin. Such resins are described in, for example, Rolland et al., US Patent Nos. 9,676,963; 9,598,606; and 9,453,142, and in Wu et al., US Patent Application Pub. No. US 2017/0260418, the disclosures of which are incorporated herein by reference.
Resins may be in any suitable form, including "one pot" resins and "dual precursor" resins (where cross-reactive constituents are packaged separately and mixed together before use, and which may be identified as an "A" precursor resin and a "B" precursor resin).
Particular examples of suitable resins include, but are not limited to, Carbon, Inc. rigid polyurethane resin (RPU), flexible polyurethane resin (FPU), elastomeric polyurethane resin (EPU), cyanate ester resin (CE), epoxy resin (EPX), or urethane methacrylate resin (UMA), all available from Carbon, Inc. (Redwood City, California).
Note that, in some embodiments employing "dual cure" polymerizable resins, the part, following manufacturing, may be contacted with a penetrant liquid, with the penetrant liquid carrying a further constituent of the dual cure system, such as a reactive monomer, into the part for participation in a subsequent cure. Such "partial" resins are intended to be included herein. See WO 2018/094131 to Feller et al.
In overview, in some embodiments, polymerizable liquids for carrying out the present invention comprise a mixture of:
(a) at least one free-radically polymerizable constituent, such as: (i) a blocked or reactive blocked prepolymer, (ii) a blocked or reactive blocked polyisocyanate, (Hi) a blocked or reactive blocked polyisocyanate chain extender, and (iv) combinations of two or three of the foregoing (e.g., in a combined amount of from 5 to 90 percent by weight),
(b) optionally, but in some embodiments preferably, at least one additional chain extender (e.g., in an amount of from 1 or 5 to 30 percent by weight when present),
(c) a free radical photoinitiator (e.g., in an amount of from 0.1 to 4 percent by weight),
(d) a free radical thermal initiator (e.g., in an amount of from 0.1 to 4 percent by weight),
(e) optionally, but in some embodiments preferably, a polyol and/or a polyamine (e.g, in an amount of from 5 to 90 percent by weight), and
(f) optionally, but in some embodiments preferably, a reactive diluent (e.g, included in an amount of from 1 to 40 percent by weight when present);
(g) optionally, but in some embodiments preferably, at least one non-reactive light absorbing pigment or dye (e.g, titanium dioxide, carbon black, and/or an organic ultraviolet light absorber) (e.g, in an amount of from 0.001 to 10 percent by weight, when present); and/or
(h) optionally, but in some embodiments preferably, a filler (e.g, in an amount of from 1 to 50 percent by weight, when present).
Details of the foregoing constituents are given in the references cited above, which are incorporated by reference herein, and in the additional description below.
Additional resin ingredients. The liquid resin or polymerizable material can have (among other things) solid particles suspended or dispersed therein. Any suitable solid particle can be used, depending upon the end product being fabricated. The particles can be metallic, organic/polymeric, inorganic, or composites or mixtures thereof. The particles can be nonconductive, semi-conductive, or conductive (including metallic and non-metallic or polymer conductors); and the particles can be magnetic, ferromagnetic, paramagnetic, or nonmagnetic. The particles can be of any suitable shape, including spherical, elliptical, cylindrical, etc. The particles can be of any suitable size (for example, ranging from 1 nm to 20 pm average diameter).
The particles can comprise an active agent or detectable compound as described below, though these may also be provided dissolved or solubilized in the liquid resin as also discussed below. For example, magnetic or paramagnetic particles or nanoparticles can be employed.
The liquid resin can have additional ingredients solubilized therein, including pigments, dyes, diluents, active compounds or pharmaceutical compounds, detectable compounds (e.g., fluorescent, phosphorescent, radioactive), etc., again depending upon the particular purpose of the product being fabricated. Examples of such additional ingredients include, but are not limited to, proteins, peptides, nucleic acids (DNA, RNA) such as siRNA, sugars, small organic compounds (drugs and drug-like compounds), etc., including combinations thereof.
Dyes/non-reactive light absorbers. In some embodiments, polymerizable liquids for carrying out the present invention include a non-reactive pigment or dye that absorbs light, particularly UV light. Suitable examples of such light absorbers include, but are not limited to: (i) titanium dioxide (e.g., included in an amount of from 0.05 or 0.1 to 1 or 5 percent by weight), (ii) carbon black (e.g., included in an amount of from 0.05 or 0.1 to 1 or 5 percent by weight), and/or (iii) an organic ultraviolet light absorber such as a a hydroxybenzophenone, hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone, hydroxypenyltriazine, and/or benzotriazole ultraviolet light absorber (e.g., Mayzo BLS® 1326) (e.g, included in an amount of 0.001 or 0.005 to 1, 2 or 4 percent by weight). Examples of suitable organic ultraviolet light absorbers include, but are not limited to, those described in US Patent Nos. 3,213,058; 6,916,867; 7,157,586; and 7,695,643, the disclosures of which are incorporated herein by reference.
Fillers. Any suitable filler may be used in connection with the present invention, depending on the properties desired in the part or object to be made. Thus, fillers may be solid or liquid, organic or inorganic, and may include reactive and non-reactive rubbers: siloxanes, acrylonitrile-butadiene rubbers; reactive and non-reactive thermoplastics (including but not limited to: poly(ether imides), maleimide-styrene terpolymers, polyarylates, polysulfones and polyethersulfones, etc.) inorganic fillers such as silicates (such as talc, clays, silica, mica), glass, carbon nanotubes, graphene, cellulose nanocrystals, etc., including combinations of all of the foregoing. Suitable fillers include tougheners, such as core-shell rubbers, as discussed below.
Tougheners. One or more polymeric and/or inorganic tougheners can be used as a filler in the present invention. The toughener may be uniformly distributed in the form of particles in the cured product. The particles could be less than 5 microns (pm) in diameter. Such tougheners include, but are not limited to, those formed from elastomers, branched polymers, hyperbranched polymers, dendrimers, rubbery polymers, rubbery copolymers, block copolymers, core-shell particles, oxides or inorganic materials such as clay, polyhedral oligomeric silsesquioxanes (POSS), carbonaceous materials (e.g., carbon black, carbon nanotubes, carbon nanofibers, fullerenes), ceramics and silicon carbides, with or without surface modification or functionalization.
Core-shell rubbers. Core-shell rubbers are particulate materials (particles) having a rubbery core. Such materials are known and described in, for example, US Patent Application Publication No. 20150184039, as well as US Patent Application Publication No. 20150240113, and US Patent Nos. 6,861,475, 7,625,977, 7,642,316, 8,088,245, and elsewhere. In some embodiments, the core-shell rubber particles are nanoparticles (/. e. , having an average particle size of less than 1000 nanometers (nm)). Generally, the average particle size of the core-shell rubber nanoparticles is less than 500 nm, e.g., less than 300 nm, less than 200 nm, less than 100 nm, or even less than 50 nm. Typically, such particles are spherical, so the particle size is the diameter; however, if the particles are not spherical, the particle size is defined as the longest dimension of the particle. Suitable core-shell rubbers include, but are not limited to, those sold by Kaneka Corporation under the designation Kaneka Kane Ace, including the Kaneka Kane Ace 15 and 120 series of products, including Kaneka Kane Ace MX 120, Kaneka Kane Ace MX 153, Kaneka Kane Ace MX 154, Kaneka Kane Ace MX 156, Kaneka Kane Ace MX170, Kaneka Kane Ace MX 257 and Kaneka Kane Ace MX 120 core-shell rubber dispersions, and mixtures thereof.
Organic diluents. In some embodiments, diluents for use in the present invention are preferably reactive organic diluents; that is, diluents that will degrade, isomerize, cross-react, or polymerize, with themselves or a light polymerizable component, during the additive manufacturing step. In general, the diluent(s) are included in an amount sufficient to reduce the viscosity of the polymerizable liquid or resin (e.g., to not more than 15,000, 10,000, 6,000, 5,000, 4,000, or 3,000 centipoise at 25 degrees Centigrade). Suitable examples of diluents include, but are not limited to, AiV-dimethylacrylamide, A-vinyl-2-pyrrolidone, and A- vinyl formamide, or a mixture if two or more thereof. The diluent may be included in the polymerizable liquid in any suitable amount, typically from 1, 5 or 10 percent by weight, up to about 30 or 40 percent by weight, or more.
Accelerators. In some embodiments, the liquid may include a deoxygenating compound as an accelerator of stereolithography (particularly CLIP). An example of a suitable such accelerator is triphenylphosphine. 2. PRODUCTION BY ADDITIVE MANUFACTURING.
Polymerizable liquids or resins as described herein may be used to make three- dimensional objects, in a "light" cure (typically by additive manufacturing) which in some embodiments generates a "green" intermediate object, followed in some embodiments by a second (typically heat) cure of that intermediate object.
Techniques for additive manufacturing are known. Suitable techniques include bottom-up or top-down additive manufacturing, generally known as stereolithography. Such methods are known and described in, for example, U.S. Patent No. 5,236,637 to Hull, US Patent Nos. 5,391,072 and 5,529,473 to Lawton, U.S. Patent No. 7,438,846 to John, US Patent No. 7,892,474 to Shkolnik, U.S. Patent No. 8,110,135 to El-Siblani, U.S. Patent Application Publication No. 2013/0292862 to Joyce, and US Patent Application Publication No. 2013/0295212 to Chen et al. The disclosures of these patents and applications are incorporated by reference herein in their entirety.
In some embodiments, the intermediate object is formed by continuous liquid interface production (CLIP). CLIP is known and described in, for example, US Patent Nos. 9,211,678, 9,205,601, 9,216,546; and in J. Tumbleston, D. Shirvanyants, N. Ermoshkin et al., Continuous liquid interface production of 3D Objects, Science 347, 1349-1352 (2015). See also R. Janusziewcz et al., Layerless fabrication with continuous liquid interface production, Proc. Natl. Acad. Sci. USA 113, 11703-11708 (2016). Other examples of methods and apparatus for carrying out particular embodiments of CLIP, or of additive manufacturing, include but are not limited to those described in B. Feller, US Patent App. Pub. No. US 2018/0243976 (published Aug. 30, 2018); M. Panzer and J. Tumbleston, US Patent App Pub. No. US 2018/0126630 (published May 10, 2018); K. Willis and B. Adzima, US Patent App Pub. No. US 2018/0290374 (Oct. 11, 2018); Batchelder et al., US Patent App Pub. No. US 2017/0129169; Sun and Lichkus, US Patent App Pub. No. US 2016/0288376; Willis et al., US Patent App Pub. No. US 2015/0360419; Lin et al., US Patent App Pub. No. US 2015/0331402; and D. Castanon, US Patent App Pub. No. US 2017/0129167, the disclosures of which are incorporated by reference herein in their entirety.
In some embodiments, CLIP employs features of a bottom-up three-dimensional fabrication as described above, but the irradiating and/or said advancing steps are carried out while also concurrently maintaining a stable or persistent liquid interface between the growing object and the build surface or window, such as by: (i) continuously maintaining a dead zone of polymerizable liquid in contact with said build surface, and (ii) continuously maintaining a gradient of polymerization zone (such as an active surface) between the dead zone and the solid polymer and in contact with each thereof, the gradient of polymerization zone comprising the first component in partially cured form. In some embodiments of CLIP, the optically transparent member comprises a semipermeable member (e.g., a fluoropolymer), and the continuously maintaining a dead zone is carried out by feeding an inhibitor of polymerization through the optically transparent member, thereby creating a gradient of inhibitor in the dead zone and optionally in at least a portion of the gradient of polymerization zone. Other approaches for carrying out CLIP that can be used in the present invention and potentially obviate the need for a semipermeable "window" or window structure include utilizing a liquid interface comprising an immiscible liquid (see L. Robeson et al., WO 2015/164234), generating oxygen as an inhibitor by electrolysis (see I. Craven et al., WO 2016/133759), and incorporating magnetically positionable particles to which the photoactivator is coupled into the polymerizable liquid (see J. Rolland, WO 2016/145182).
After the intermediate three-dimensional object is formed, it is optionally cleaned, optionally dried (e.g., air dried) and/or rinsed (in any sequence). It is then further cured, preferably by heating (although further curing may in some embodiments be concurrent with the first cure, or may be by different mechanisms such as contacting to water, as described in US Patent No. 9,453,142 to Rolland et ah).
3. CLEANING OR WASHING.
Objects as described above can be cleaned in any suitable apparatus, in some embodiments with a wash liquid as described herein, and in other embodiments by wiping (with an absorbent, air blade, etc.) spinning, or variations thereof.
Wash liquids that may be used to carry out the present invention include, but are not limited to, water, organic solvents, and combinations thereof (e.g., combined as co-solvents), optionally containing additional ingredients such as surfactants, chelants (ligands), enzymes, borax, dyes or colorants, fragrances, etc., including combinations thereof. The wash liquid may be in any suitable form, such as a solution, emulsion, dispersion, etc.
In some preferred embodiments, where the residual resin has a boiling point of at least 90 or 100 °C (e.g, up to 250 or 300 °C, or more), the wash liquid has a boiling point of at least 30 °C, but not more than 80 or 90 °C. Boiling points are given herein for a pressure of 1 bar or 1 atmosphere.
In some embodiments, the wash liquid consists of a 50:50 (volume: volume) solution of water and an alcohol organic solvent such as isopropanol (2-propanol). Examples of hydrofluorocarbon solvents that may be used to carry out the present invention include, but are not limited to, l,l,l,2,3,4,4,5,5,5-decafluoropentane (Vertrel® XF, DuPont™ Chemours), l,l,l,3,3-pentafluoropropane, l,l,l,3,3-pentafluorobutane, etc.
Examples of hydrochlorofluorocarbon solvents that may be used to carry out the present invention include, but are not limited to, 3,3-dichloro-l,l,l,2,2-pentafluoropropane, l,3-dichloro-l,l,2,2,3-pentfluoropropane, l,l-dichloro-l-fluoroethane, etc., including mixtures thereof.
Examples of hydrofluoroether solvents that may be used to carry out the present invention include, but are not limited to, methyl nonafluorobutyl ether (HFE-7100), methyl nonafluoroisobutyl ether (HFE-7100), ethyl nonafluorobutyl ether (HFE-7200), ethyl nonafluoroisobutyl ether (FIFE-7200), l,l,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, etc., including mixtures thereof. Commercially available examples of this solvent include Novec 7100 (3M), Novec 7200 (3M).
Examples of volatile methylsiloxane solvents that may be used to carry out the present invention include, but are not limited to, hexamethyldisiloxane (OS -10, Dow Corning), octamethyltrisiloxane (OS-20, Dow Coming), decamethyltetrasiloxane (OS-30, Dow Coming), etc., including mixtures thereof.
Other siloxane solvents (e.g., NAVSOLVE™ solvent) that may be used to carry out the present invention include but are not limited to those set forth in US Patent No. 7,897,558.
In some embodiments, the wash liquid comprises an azeotropic mixture comprising, consisting of, or consisting essentially of a first organic solvent (e.g, a hydrofluorocarbon solvent, a hydrochlorofluorocarbon solvent, a hydrofluoroether solvent, a methylsiloxane solvent, or a combination thereof; e.g, in an amount of from 80 or 85 to 99 percent by weight) and a second organic solvent (e.g, a C1-C4 or C6 alcohol such as methanol, ethanol, isopropanol, tert- butanol, etc.; e.g, in an amount of from 1 to 15 or 20 percent by weight). Additional ingredients such as surfactants or chelants may optionally be included. In some embodiments, the azeotropic wash liquid may provide superior cleaning properties, and/or enhanced recyclability, of the wash liquid. Additional examples of suitable azeotropic wash liquids include, but are not limited to, those set forth in US Patent Nos. 6,008,179; 6,426,327; 6,753,304; 6,288,018; 6,646,020; 6,699,829; 5,824,634; 5,196,137; 6,689,734; and 5,773,403, the disclosures of which are incorporated by reference herein in their entirety.
When the wash liquid includes ingredients that are not desired for carrying into the further curing step, in some embodiments the initial wash with the wash liquid can be followed with a further rinsing step with a rinse liquid, such as water (e.g., distilled and/or deionized water), or a mixture of water and an alcohol such as isopropanol.
4. FURTHER CURING.
After washing, the object is in some embodiments further cured, preferably by heating or baking.
Heating may be active heating (e.g., in an oven, such as an electric, gas, solar oven or microwave oven, heated bath, or combination thereof), or passive heating (e.g., at ambient (room) temperature). Active heating will generally be more rapid than passive heating and in some embodiments is preferred, but passive heating— such as simply maintaining the intermediate at ambient temperature for a sufficient time to effect further cure— is in some embodiments preferred.
In some embodiments, the heating step is carried out at at least a first (oven) temperature and a second (oven) temperature, with the first temperature greater than ambient temperature, the second temperature greater than the first temperature, and the second temperature less than 300 °C (e.g., with ramped or step-wise increases between ambient temperature and the first temperature, and/or between the first temperature and the second temperature).
For example, the intermediate may be heated in a stepwise manner at a first temperature of about 70°C to about l50°C, and then at a second temperature of about 150°C to 200 or 250 °C, with the duration of each heating depending on the size, shape, and/or thickness of the intermediate. In another embodiment, the intermediate may be cured by a ramped heating schedule, with the temperature ramped from ambient temperature through a temperature of 70 to 150 °C, and up to a final (oven) temperature of 250 or 300 °C, at a change in heating rate of 0.5°C per minute, to 5 °C per minute. (See, e.g., US Patent No. 4,785,075).
In some embodiments, the heating step is carried out in an inert gas atmosphere. Inert atmosphere ovens are known, and generally employ an atmosphere enriched in nitrogen, argon, or carbon dioxide in the oven chamber. Suitable examples include but are not limited to those available from Grieve Corporation, 500 Hart Road Round Lake, Illinois 60073-2898 USA, Davron Technologies, 4563 Pinnacle Lane, Chattanooga, TN 37415 USA, Despatch Thermal Processing Technology, 8860 207th Street, Minneapolis, MN 55044 USA, and others. In other embodiments, the heating step is carried out in an inert liquid bath. Suitable inert liquids may be aqueous liquids (i.e., pure water, salt solutions, etc.), organic liquids (e.g., mineral oil, fluorinated, perfluorinated, and polysiloxane organic compounds such as perfluorohexane, perfluoro(2-butyl-tetrahydrofurane), perfluorotripentylamine, etc. (commercially available as PERFLUORINERT® inert liquids from 3M Company), and mixtures thereof. These inert liquids can be deoxygenated if necessary, such as by bubbling an inert gas such as nitrogen through the liquid, by boiling the inert liquid, by mixing oxygenscavenging agents with the inert liquid medium (or contacting them to one another), etc., including combinations thereof (see, e.g., US Patent No. 5,506,007).
In some embodiments, the further curing or heating step (whether carried out in a liquid or gas fluid) is carried out at an elevated pressure (e.g, elevated sufficiently to reduce volatilization or out-gassing of residual monomers, prepolymers, chain extenders, and/or reactive diluents, etc.). Suitable pressure ranges are from 10 or 15 psi to 70 or 100 psi, or more.
5. IMPREGNATION WITH ADDITIVES.
Examples of additives that may be used in carrying out the present invention include, but are not limited to, colorants, ultraviolet light stabilizers or absorbing compounds, flame retardants, heat stabilizers, antioxidant agents, antistatic agents, radiation stabilizers, and combinations thereof.
In some embodiments, the colorant comprises a blue, red, orange, yellow, green, violet, brown or black pigment or dye, or a combination of two or more thereof.
In some embodiments, the colorant comprises a non-reactive pigment or dye that absorbs light, particularly UV light. Suitable examples of such light absorbers include, but are not limited to: (i) titanium dioxide (e.g., included in an amount of from 0.05 or 0.1 to 1 or 5 percent by weight), (u) carbon black (e.g, included in an amount of from 0.05 or 0.1 to 1 or 5 percent by weight), and/or (Hi) an organic ultraviolet light absorber such as a a hydroxybenzophenone, hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone, hydroxypenyltriazine, and/or benzotriazole ultraviolet light absorber (e.g., Mayzo BLS1326). Examples of suitable organic ultraviolet light absorbers include, but are not limited to, those described in US Patent Nos. 3,213,058; 6,916,867; 7,157,586; and 7,695,643, the disclosures of which are incorporated herein by reference.
In some embodiments, the ultraviolet (UV) light stabilizers or absorbing compounds are, in general, polysubstituted linear polyacenes (e.g, naphthalene, anthracene, tetracene, pentacene, hexacene). The compounds are polysubstituted with two or more of bromo, chloro, -Se-R’, -S-R’, or combinations thereof, where each R’ is independently selected from alkyl, aryl, and arylalkyl. Additional examples include, but are not limited to, benzotriazoles and benzophenones, hindered amine light stabilizers (HALS), and benzoates (available from Mayzo, Suwanee, Georgia).
Examples of antioxidant agents include, but are not limited to, phenols, hindered phenols, phosphites, thiosynergists, and combinations thereof (available from Mayzo, Suwanee, Georgia).
Examples of flame retardant additives include, but are not limited to, alumina trihydrate, magnesium hydroxide, etc.
Examples of heat stabilizers include, but are not limited to, organophosphites, phenolic antioxidants, etc.
Examples of radiation stabilizers include, but are not limited to, light stabilizers such as UV absorbers, quenchers, and hindered amine stabilizers.
Examples of antistatic additives include, but are not limited to, imidazolinium, pyridinium, piperidinium and morpholinium salts. Additional examples of antistatic additive include, but are not limited to, monoglycerides, diglycerides, glycerol esters, polyglycerol esters, etc. (available from Palsgaard®, Morris Plains, New Jersey).
Additional examples of ultraviolet light stabilizers or absorbing compounds, colorants, flame retardants, heat stabilizers, antioxidant agents, and radiation stabilizers include, but are not limited to, those set forth in US Patent Nos. 10,000,636; 9,988,483; 9,938,401; 8,883,044; 7,479,326; 6,933,344; 4,341,885; and 4,167,503, the disclosures of which are incorporated herein by reference in their entirety.
The additive may be combined with a solvent such as an alcohol solvent (optionally including water), and then the object, after it is further cured, impregnated with the additive by immersing the object in the solvent, at least partially, as described above and below.
In some embodiments, the solvent comprises or consists essentially of methanol, ethanol, propanol ( e.g isopropyl alcohol, IP A), butanol (e.g., n-butanol), or a combination thereof, optionally in combination with up to 30, 40, or 50 percent (by volume) water.
In some embodiments, the immersing step is carried out at a temperature of from 20 or 25 degrees centigrade to 30, 40, or 50 degrees Centigrade.
In some embodiments, immersing step is carried out at ambient temperature and/or ambient pressure. In other embodiments, the immersing step is carried out at an elevated temperature (that is, with heating) and/or elevated pressure (e.g., in an enclosed pressure vessel).
The immersing step may be carried out for any suitable time, such as from 1, 2, or 3 hours, to 12 or 24 hours.
In some embodiments, the object is only partially immersed in the impregnation solution, and only that portion of the object immersed is at least partially impregnated with the at least one additive.
In some embodiments, the object is at least partially immersed under conditions only sufficient to only partially impregnate the object with the additive (for example, when the object is partially impregnated with a pigment or dye, to provide a surface wear indicator feature to the finished object).
The present invention is explained in greater detail in the following non-limiting Examples.
EXAMPLE
A green intermediate object in the form of an open lattice was produced by continuous liquid interface production from a polyurethane dual cure additive manufacturing resin, washed, and then baked in an oven to produce a cured object, still in the form of an open polymer lattice, in accordance with known techniques.
An impregnating solution of approximately two grams of rhodamine pigment (rhodamine 6G from Sigma, product no R4127) in isopropanol (99% v/v with water) was prepared.
The finished object, after baking, was immersed in the impregnation solution at ambient temperature (approximately 25 degrees centigrade), for approximately six hours. The immersed portion was strongly colored by the rhodamine pigment, as shown in FIG. 1.
On cutting into the lattice, the dye was seen to have impregnated below the surface of the object, partially into the polymer lattice structures themselves, as schematically illustrated in FIG. 2, where the drawing on the left represents a cross-section of a portion of a lattice prior to the immersing step, and the drawing on the right represents a cross-section of the same portion of the lattice following the immersing step.
The extent of impregnation is adjusted by adjusting the time, temperature, and/or pressure at which the immersing step is carried out, with deeper impregnation being achieved by increasing time, temperature, and/or pressure. The foregoing is illustrative of the present invention, and is not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.