Method and system for processing a photopolymerizable composition

Abstract

The present disclosure provides a method including the steps of obtaining an insert including sieves defining openings each having a diameter of 10 to 200 micrometers, disposing a volume of fluid including a photopolymerizable composition and contaminants in the insert, and subjecting the volume of fluid to centrifugal force to retain the contaminants within the insert and to force at least a portion of the photopolymerizable composition through the sieves of the insert, thereby separating the contaminants from at least a portion of the photopolymerizable composition to provide a separated photopolymerizable composition. Also provided is a system including an additive manufacturing apparatus, a centrifuge, and an insert configured to be inserted into the centrifuge. The method and system can advantageously aid in recovering contaminated photopolymerizable composition for reuse.

Description

[Technical Field]

[0001] This disclosure relates to a method for processing photopolymerizable compositions to remove contaminants from them, and to a system for processing compositions for use in, for example, additive manufacturing technology. [Background technology]

[0002] Photopolymerizable compositions have been used in many industries, including the use of additive manufacturing technologies. While articles may be formed by polymerizing less than the total volume of the photopolymerizable composition, the remaining portion often contains one or more contaminants generated during the polymerization process. [Overview of the project]

[0003] A method and system for processing photopolymerizable compositions are provided.

[0004] In a first embodiment, a method is provided. The method includes the steps of: a) obtaining an insert comprising a sieve defining a plurality of openings, each having a diameter of 10 to 200 micrometers; b) placing a certain volume of fluid, comprising a fluid containing a photopolymerizable composition and contaminants, into the insert; and c) separating the contaminants from at least a portion of the photopolymerizable composition by applying centrifugal force to the certain volume of fluid to retain the contaminants in the insert and allowing at least a portion of the photopolymerizable composition to pass through the sieve of the insert, thereby providing a separated photopolymerizable composition.

[0005] In a second embodiment, a system is provided, the system comprising: a) an additive manufacturing apparatus; b) a centrifuge; and c) an insert configured to be inserted into the centrifuge, the insert comprising a sieve defining a plurality of openings, each having a diameter of 10 to 200 micrometers.

[0006] This method and system may be useful for removing contaminants from photopolymerizable compositions in order to reduce the amount of photopolymerizable compositions containing contaminants that are discarded as waste or recycled, leading to the production of lower-quality three-dimensional objects.

[0007] The above “Summary of the Invention” in this disclosure is not intended to describe each or all of the disclosed embodiments of the Invention. The following description more specifically illustrates exemplary embodiments. In several places throughout this application, guidance is provided through the enumeration of examples, which can be used in various combinations. In each example, the enumerated items described serve only as representative groups and should not be construed as an exclusive enumeration. Accordingly, the scope of this disclosure should not be limited to the specific exemplary structures described herein, but extends to at least the structures described by the language of the claims, and their equivalents. Any element that is actively described as an option herein may be expressly included in the claims or excluded from the claims in any combination as desired. Various theories and possible mechanisms may be considered herein, but in no case shall such considerations limit the subject matter of the claims. [Brief explanation of the drawing]

[0008] [Figure 1] This is a flowchart illustrating an exemplary method of the present disclosure. [Figure 2A] This is a schematic perspective view of an additive manufacturing device. [Figure 2B] This is a schematic perspective view of a centrifuge. [Figure 2C] This is a schematic perspective view of an exemplary insert partially positioned within a container, as disclosed herein. [Figure 2D] Figure 2C is a schematic perspective cross-sectional view of the insert and container. [Figure 3A] This is a schematic perspective view of an exemplary insert partially positioned within a container according to the present disclosure, which holds a certain volume of fluid. [Figure 3B] This is a schematic perspective view of an exemplary insert partially positioned within a container, as disclosed herein. [Figure 4] This is a schematic top view of an exemplary sieve having a plurality of star-shaped openings according to the present disclosure. [Figure 5] This is a schematic perspective exploded view of an exemplary insert having two sieves according to the present disclosure. [Figure 6] This is a photograph of contaminants recovered from a photopolymerizable composition. [Modes for carrying out the invention]

[0009] It has been discovered that contaminants can be removed from photopolymerizable compositions to enable their reuse. In at least certain embodiments, the washed photopolymerizable composition is clean enough to be used in the same batch as a certain volume of unused (e.g., initial) photopolymerizable composition. Even compositions having a viscous and / or paste-like consistency can be successfully decontaminated using methods or systems according to at least certain embodiments of this disclosure.

[0010] For example, depending on the specific geometry of a three-dimensional object (e.g., a printed part), unintended undercuts in the printed geometry may result in small pieces of resin curing without sufficient adhesion to the rest of the printed part, contaminating the remaining photopolymerizable composition. These small pieces may have the size of one or more voxels. Another problem may be that after repeated use, one or more surfaces of the liquid bath may show increased adhesion during printing, potentially causing parts or entire sections of the supporting geometry to break and contaminate the liquid bath. Further contamination may include, for example, dust from the ambient air, but such contamination can be minimized, for example, by using a laminar flow system to apply cleanroom conditions. However, it is not practical to completely prevent contaminants such as small broken pieces and dust while printing multiple parts in a single liquid bath.

[0011] Glossary As used herein, "actinic radiation" encompasses UV rays, electron beam radiation, visible light, infrared rays, gamma rays, and any combination thereof.

[0012] As used herein, a "monomer" is a single unit molecule that can form an oligomer or a polymer by itself or in combination with other monomers, an "oligomer" is a component having from 2 to 9 repeating units, and a "polymer" is a component having 10 or more repeating units.

[0013] As used herein, an "aliphatic group" means a saturated or unsaturated straight-chain, branched-chain, or cyclic hydrocarbon group. This term is used as encompassing, for example, alkyl groups, alkenyl groups, and alkynyl groups.

[0014] As used herein, "alkyl" means a straight-chain or branched-chain, cyclic or acyclic, saturated monovalent hydrocarbon having from 1 to 32 carbon atoms, such as methyl, ethyl, 1-propyl, 2-propyl, pentyl, and the like.

[0015] As used herein, "alkylene" means a straight-chain saturated divalent hydrocarbon having from 1 to 12 carbon atoms, or a branched-chain saturated divalent hydrocarbon group having from 2 to 12 carbon atoms, such as methylene, ethylene, propylene, 2-methylpropylene, pentylene, hexylene, and the like.

[0016] As used herein, "alkenyl" refers to a monovalent straight-chain or branched-chain unsaturated aliphatic group having one or more carbon-carbon double bonds, such as vinyl. Unless otherwise specified, an alkenyl group typically contains from 2 to 20 carbon atoms.

[0017] As used herein, "alkenediyl" refers to a straight-chain, branched-chain, or cyclic divalent unsaturated aliphatic group, such as -CH=CH-, -CH=C(CH3)CH2-, -CH=CHCH2-, etc. Unless otherwise specified, an alkenediyl group typically contains 2 to 20 carbon atoms.

[0018] As used herein, the term "aryl" refers to a monovalent group that is a group of an aromatic carbocyclic compound. An aryl group has at least one aromatic carbocyclic ring and may have 1 to 5 optional rings bonded or fused to the aromatic carbocyclic ring. The additional rings can be aromatic, aliphatic, or a combination thereof. An aryl group usually has 5 to 20 carbon atoms.

[0019] As used herein, the term "substituted aryl" refers to an aryl group substituted with at least one alkyl group, substituted with at least one alkoxy group, or substituted with at least one alkyl group and at least one alkoxy group. A substituted aryl group contains 6 to 40 carbon atoms. A substituted aryl group often contains an aryl group having 5 to 20 carbon atoms and an alkyl group and / or an alkoxy group each having 1 to 20 carbon atoms.

[0020] As used herein, the term "aralkyl" refers to an alkyl group substituted with at least one aryl group. An aralkyl group contains 6 to 40 carbon atoms. An aralkyl group often contains an alkyl group having 1 to 20 carbon atoms and an aryl group having 5 to 20 carbon atoms.

[0021] As used herein, the term "ethylenically unsaturated" refers to a double bond between two carbon atoms, such as vinyl ether (H2C=CHO), vinyl ester (H2C=CHOCO), styrene (e.g., vinylbenzene), and alkenyl (H2C=CH(CH2) nThe formula includes functional groups such as vinyl (H2C=CH-) [wherein n is typically in the range of 1 to 30 or 1 to 20 or 1 to 10]. Ethylene unsaturated groups also include (meth)acrylamides (H2C=CHCONH- and H2C=CH(CH3)CONH-), as well as (meth)acrylics such as (meth)acrylates (CH2=CHCOO- and CH2=C(CH3)COO-).

[0022] As used herein, "(meth)acrylate" is an abbreviation for acrylate, methacrylate, or a combination thereof; "(meth)acrylic" is an abbreviation for acrylic, methacrylic, or a combination thereof; and "(meth)acrylic" is an abbreviation for acrylic and methacrylic groups. "Acrylic" refers to derivatives of acrylic acid, such as acrylate, methacrylate, acrylamide, and methacrylamide. "(meth)acrylic" means a monomer or oligomer having at least one acrylic or methacrylic group, which, if it contains two or more groups, is linked by an aliphatic segment. As used herein, "(meth)acrylate-functional compound" is, in particular, a compound containing a (meth)acrylate moiety. The term "(meth)acryloyl" is defined by the formula CH2=CHR b -(CO)-[wherein, R b [where is hydrogen or methyl, and the group -(CO)- refers to a carbonyl group.]

[0023] As used herein, “diameter” refers to the longest straight line length across a shape (two-dimensional or three-dimensional) that intersects the center of the shape.

[0024] As used herein, “fluid” refers to emulsions, dispersions, suspensions, solutions, and pure components having a continuous liquid phase, excluding powders and particulates in solid form.

[0025] As used herein, “liquid” refers to a state of matter that is neither solid nor gas, but has a fixed volume and amorphous form.

[0026] As used herein, “curing” and “polymerization” mean hardening or partial hardening of a composition by any mechanism, such as heat, light, radiation, electron beam, microwave, chemical reaction, or a combination thereof.

[0027] As used herein, “cured” refers to a material or composition that has been hardened or partially hardened by one or more curing mechanisms (e.g., polymerized or crosslinked).

[0028] As used herein, “photopolymerizable” refers to a composition containing at least one material that can be cured or partially cured using chemical rays.

[0029] As used herein, “initial photopolymerizable composition” refers to a photopolymerizable composition in which none of its volume has been exposed to chemical radiation, and which includes the total amount of each component of the formulation and does not include any contaminants formed during curing.

[0030] As used herein, “separated photopolymerizable composition” refers to a composition containing at least one material that can be cured or partially cured using chemical radiation, and containing less than the total amount of at least one component of the formulation. The separated photopolymerizable composition has been exposed to chemical radiation in part by volume. The separated photopolymerizable composition has also been subjected to a process for separating at least one contaminant from the photopolymerizable composition.

[0031] As used herein, “contaminant” refers to material placed in a photopolymerizable composition that was not intentionally included in the composition formulation. A contaminant may include at least one of oligomers, polymers, dust particles, dust, multiple cured voxels formed from the photopolymerizable composition, or components formed from polymerization products of the photopolymerizable composition.

[0032] The term "mass inertial force," when referred to herein, may be defined as force per unit mass, and therefore, in units of m / s².2 It can be defined as follows. Furthermore, the mass inertial force can be expressed by the G force, which is an element of gravitational acceleration. For the purposes of this specification, gravitational acceleration is 9.81 m / s². 2 Therefore, for example, 9.81 m / s 2 The inertial force of the mass can be expressed as 1G.

[0033] Furthermore, in this specification, all numbers are assumed to be modified with the term “approximately,” and preferably with the term “exactly.” When used herein, in relation to a measured quantity, the term “approximately” refers to the variation in the measured quantity that can be predicted by a person skilled in the art who performs the measurement and exercises a level of care commensurate with the purpose of the measurement and the precision of the measuring instrument used. Moreover, in this specification, the description of a numerical range by endpoints includes all numbers and their endpoints that are contained within that range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0034] When used herein as a modifier for a characteristic or attribute, the term “generally” means, unless otherwise specified, that the characteristic or attribute is readily recognizable to a person skilled in the art, but does not require absolute precision or perfect agreement (e.g., within ±20% for quantifiable characteristics). The term “substantially” means, unless otherwise specified, a high degree of approximation (e.g., within ±10% for quantifiable characteristics), but again, does not require absolute precision or perfect agreement. Terms such as identical, equal, uniform, constant, and strictly are understood to mean that they do not require absolute precision or perfect agreement, but are within the normal tolerance or measurement error applicable to the particular situation.

[0035] method In the first aspect, a method is provided. The method is a) A step of obtaining an insert comprising a sieve defining a plurality of openings, each having a diameter of 10 to 200 micrometers, b) The step of placing a certain volume of fluid containing a photopolymerizable composition and a contaminant into an insert, c) The step of applying centrifugal force to a certain volume of fluid to retain contaminants within the insert and allowing at least a portion of the photopolymerizable composition to pass through a sieve in the insert, thereby separating the contaminants from at least a portion of the photopolymerizable composition and providing the separated photopolymerizable composition.

[0036] Referring to Figure 1, a flowchart of the method according to the first embodiment is provided. More specifically, the method comprises a) a step 110 of obtaining an insert comprising a sieve defining a plurality of openings, each having a diameter of 10 to 200 micrometers, and b) a step 120 of placing a certain volume of fluid, comprising a photopolymerizable composition and contaminants, into the insert.

[0037] In some embodiments, the insert is placed in the centrifuge before the fluid is deposited in the insert. In some embodiments, the insert is placed in the centrifuge after the fluid has been deposited in the insert. The configuration of the insert may vary, insofar as the insert includes a sieve and defines an opening area for holding a certain volume of fluid. Referring to Figure 3A, an exemplary insert 320 (coupled to each of the container 330 and stand 350) is shown placed on a laboratory scale 300. Weighing the insert 320 after the fluid 370 has been added helps to achieve a favorable equilibrium of mass during the application of centrifugal force, when a weight containing the fluid or another insert is subjected to centrifugal force simultaneously with the insert 320. For example, Figure 2B shows an insert 220 containing fluid 270 and placed in a cup 260 set up in a centrifuge 290. A sieve 240 having the form of a nonwoven fabric is partially located inside the insert 220, with the edges of the sieve 240 outside the insert 220. On the opposite side of insert 220, another cup 260 contains an object 280 that provides a balanced mass within the centrifuge 290. In some embodiments, the method further includes the step of balancing the centrifuge by placing a certain volume of fluid in a second insert of the centrifuge, located opposite the (e.g., first) insert, before applying centrifugal force to a certain volume of fluid.

[0038] In some embodiments, the centrifuge includes a sensor that measures imbalance and terminates centrifugal force if the imbalance exceeds (e.g., a predetermined) threshold amount. By monitoring the equilibrium state of the contents of the centrifuge during the application of centrifugal force, it is possible to detect with high sensitivity that two or more samples are exhibiting different flow rates of the photopolymerizable composition through the sieve due to clogging of at least some of the sieve openings. Measuring such imbalance allows any sieve with an unacceptable degree of clogging to be cleaned or replaced before further application of centrifugal force. Alternatively, sieve clogging can be detected using other measurement methods, such as measuring the packing level of the photopolymerizable composition in one or more inserts using ultrasonic or optical sensors.

[0039] The method further includes step 130 of separating the contaminants from at least a portion of the photopolymerizable composition by applying centrifugal force to a certain volume of fluid to retain the contaminants within the insert and allowing at least a portion of the photopolymerizable composition to pass through a sieve in the insert, thereby providing the separated photopolymerizable composition. The centrifugal force used may be greater than 1G, 1.5G or more, 2G, 2.5G, 3G, 3.5G, 4G, 5G, 6G, 7G, 8G, 9G, 10G, 11G, 12G, 13G, 14G, 15G, 16G, 17G, 18G, 19G, or 20G or more; and 100G or less, 90G, 85G, 80G, 75G, 70G, 65G, 60G, 55G, 50G, 45G, or 40G or less. Those skilled in the art can determine suitable parameters based on the viscosity of a particular fluid; fluids with higher viscosity and / or paste-like viscosity typically require higher centrifugal force to propel the fluid through the sieve opening. In contrast, materials with very low viscosity can pass through the sieve with minimal centrifugal force, and using high centrifugal force risks fragmentation during centrifugation, especially if the parts are made of fragile material.

[0040] Advantageously, centrifugal force is typically applied to a fluid at ambient pressure. This is in contrast to methods of separating contaminants from photopolymerizable compositions that require the use of either negative pressure (e.g., vacuum) or positive pressure to move the photopolymerizable composition through a filter in order to effectively separate contaminants from the photopolymerizable composition. The use of positive or negative pressure would introduce an undesirable additional complexity into the method or system. In some embodiments, the photopolymerizable compositions for which the methods described herein are useful exhibit shear-deviscating behavior. Such behavior helps to successfully separate contaminants from the photopolymerizable composition because the centrifugal force imparts a shear force to the photopolymerizable composition, causing it to thin and its viscosity to decrease, thus encouraging the photopolymerizable composition to pass through the sieve into the container. The methods disclosed herein are also suitable for fluids that exhibit Newtonian viscous behavior. Furthermore, certain methods have already used a centrifuge to remove the uncured photopolymerizable composition from a three-dimensional object, and therefore contaminants can be advantageously removed from the fluid using the same centrifuge.

[0041] In some embodiments, the separated photopolymerizable composition further comprises particulate fillers. Any particulate fillers present in the fluid are small enough to pass through the sieve openings and will therefore be understood to have an effective diameter of less than 200 micrometers, 175, 150, 125, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10, 8, 6, 4, 2, or 1 micrometer. In certain embodiments, the particulate filler comprises nanoparticles, at least one dimension of the particulate filler being less than 1 micrometer, for example, 950 nanometers or less, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, or 300 nanometers or less; and 1 nanometer or more, 2, 5, 7, 10, 12, 15, 18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 125, 150, 175, 200, 225, 250, or 275 nanometers or more. Some suitable particulate fillers include, but are not limited to, yttrium, strontium, barium, zirconium, hafnium, niobium, tantalum, tungsten, bismuth, molybdenum, tin, zinc, lanthanide elements (i.e., elements with atomic numbers in the range of 57 to 71, including the edge values), cerium, and oxides of combinations thereof. Examples of non-aggregated silicon dioxide (silica) nanoparticles are those commercially available from Nalco Chemical Co. (Naperville, IL) under the product name NALCO COLLOIDAL SILICAS, e.g., NALCO products #1040, 1042, 1050, 1060, 2327, and 2329, as well as silica nanoparticles described in U.S. Patent No. 6,899,948 (Zhang et al.) and U.S. Patent No. 6,572,693 (Wu et al.).

[0042] In some embodiments, at least a portion of the insert is placed in a container configured to fit into a centrifuge, and a portion of the photopolymerizable composition passing through the insert's sieve is collected in the container. Referring to Figures 2C and 2D, schematic diagrams of an exemplary insert 220 partially placed in a container 230 are provided. The insert 220 is positioned above the majority of the volume of the container 230 when in use, helping to pass the photopolymerizable composition from the insert 220 to the container 230 below with the help of centrifugal force and gravity. The sieve 240 is located within the insert 220. The sieve 240 may be formed integrally with the insert 220, or it may be a separate item configured to be placed inside the insert 220. The sieve 240 is typically located adjacent to or inside the container 230.

[0043] In the embodiments shown in Figures 2C and 2D, the container 230 is partially supported by a stand 250 having at least two legs 252 supporting a body 254. The body 254 of the stand 250 is configured to at least partially surround the insert 220. In certain embodiments, the stand 250 further comprises a ledge 256 configured to support the insert 220. Collectively, the insert 220, container 230, sieve 240, and stand 250 can be advantageously (e.g., removable) arranged within the cup 260. In preferred embodiments, the stand 250 is configured to minimize the movement of the insert 220 and container 230 within the cup 260 while subjected to centrifugal force. Similarly, the cup 260 can be sized to fit into a specific device (e.g., a centrifuge) that applies centrifugal force to a certain volume of fluid within the insert 220.

[0044] Providing a stand is optional. In embodiments without a stand, for example, the insert may have a size and shape complementary to the inner surface of the cup that fits into a device that applies centrifugal force (e.g., a centrifuge).

[0045] Figure 3B is a schematic perspective view of another exemplary insert partially positioned within a container. In this embodiment, the external dimensions of the insert 320 are sized to fit into a cup 360, which also functions as a container for receiving the separated photopolymerizable composition that passes through the sieve 340 of the insert 320. The embodiment shown in Figure 3B is shown assembled and ready to be subjected to centrifugal force and includes, for example, the insert 320 supported by a stand 350, all positioned within the container / cup 360. The top of the insert 320 is positioned above the top of the container / cup 360. The stand 350 in this embodiment includes a solid wall 355 that surrounds at least some of the outside of the insert 320 and provides stability to the insert 320 within the container / cup 360. The stand 350 includes a plurality of legs 352 that support the stand 350 within the container / cup 360 and come into contact with the separated photopolymerizable composition as it passes through the sieve 340 and enters the container / cup 360. Other configurations may be used to provide an insert partially positioned within the container.

[0046] Referring to Figure 4, a schematic top view of an exemplary sieve 440 having a plurality of openings 442, each having a star shape, is provided. The shape of the openings of the sieve is not particularly limited and in some embodiments include one or more of circular, elliptical, quadrilateral, triangular, or star shapes. In some embodiments, a preferred sieve is a woven material having quadrilateral (e.g., square or rectangular) openings. As described above, the sieve according to the present disclosure defines a plurality of openings, each having a diameter of 10 to 200 micrometers. In some embodiments, the openings have diameters of 10 micrometers or more, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, or 75 micrometers or more; and 200 micrometers or less, 190, 180, 170, 160, 150, 140, 130, 120, 110, 100, 95, 90, 85, or 80 micrometers or less. The opening size can be selected based on the minimum opening that allows the particulate filler to pass through without the opening becoming clogged before the separation of the photopolymerizable composition from the contaminants is complete.

[0047] Figure 4 shows a line 443 indicating where the diameter of one star-shaped opening 442 is measured. In this case, the star-shaped opening 442 has points of equal size, and therefore the diameter 443 can be determined by measuring the length of a straight line starting from any one of the points, passing through the center of the star, and to the opposing edges of the star-shaped opening 442. The positions of one point 444 and the center 445 are shown (for clarity) on another star-shaped opening 442. If the points of the star are not all the same, the diameter 443 is determined by starting the measurement from the point furthest from the center of the star-shaped opening 442.

[0048] Referring to Figure 5, a schematic perspective exploded view of another exemplary insert 520 partially positioned within the container 530 is provided. In this embodiment, the insert 520 is integrally formed with a stand 550, which is sized to fit within the cup 560. For example, the lower part of the insert wall 522 may be configured to nest within the upper part of the container wall 532. Other configurations may be used to provide an insert partially positioned within the container. The upper part of the insert 520 is positioned above the top of the cup 560 when the components are assembled. The stand 550 in this embodiment includes a plurality (e.g., four) of legs 552 for supporting the insert 520 within the cup 560. In this embodiment, sieve 540 is a first sieve, and the insert 520 further includes a second sieve 546 positioned adjacent to the first sieve 540, the second sieve 546 defining a plurality of openings, each having a smaller diameter than the plurality of openings of the first sieve 540. The use of the first sieve with larger openings can hold larger contaminants (less clogging than if only the second sieve were used), while the second sieve can hold smaller contaminants than the first sieve. The embodiment shown in Figure 5 further includes a removable sieve stabilizer 529, which helps to hold one or more sieves 540, 546 in place when they are in a predetermined position on top of the insert 520, especially when the sieves (e.g., 546) contain nonwoven fabric. In this embodiment, the removable sieve stabilizer 529 has a cylindrical shape, but other shapes may also be useful. Collectively, the removable sieve stabilizer 529, the integrated insert 520 and stand 550, the sieves 540 and 546, and the container 530 can be advantageously (for example, removable) arranged within the cup 560.

[0049] Typical contaminant materials that may be present in a photopolymerizable composition include, but are not limited to, one or more oligomers, polymers, dust particles, dust, parts formed from polymerization products of the photopolymerizable composition, or multiple cured voxels (e.g., very small parts) formed from the photopolymerizable composition. Figure 6 is a photograph of contaminants recovered from a photopolymerizable composition, including parts 602a, 602b, dust 604a, 604b, and multiple cured voxels 606, all formed from polymerization products of the photopolymerizable composition. Part 602a has an irregular shape and is likely to have been broken off from a larger part. Part 602b has a rectangular prism shape. As used herein, the term “dust” includes microfibers that may exist individually, together with one or more other microfibers, or as an accumulation of many microfibers. Dust may also be present in or on top of dust. In Figure 6, two thorny dust particles 604a and a separate cluster of dust particles 604b are visible on part 602b. Multiple cured voxels 606 have a length of approximately 200 micrometers.

[0050] Optionally, the method according to the present disclosure further comprises the step of d) subjecting the separated photopolymerizable composition to homogenization. Homogenization may be useful to ensure that any particulate fillers present are suspended generally uniformly throughout the separated photopolymerizable composition. Homogenization can be carried out using a kneader, hand mixer, speed mixer, sonicator, mill, etc. In selected embodiments, a kneader or mixer is preferred for homogenization. Homogenization may be carried out under vacuum. Advantageously, when using a kneader, it is possible to apply vacuum to remove dissolved gases and bubbles from the photopolymerizable composition during homogenization. In some embodiments, the container for receiving the separated photopolymerizable composition can be selected to be compatible with the homogenization apparatus, and therefore it is not necessary to transfer the separated photopolymerizable composition to a different container for homogenization. It should be noted that the centrifugal force applied to the fluid also helps to remove some bubbles from the photopolymerizable composition when it is separated from contaminants. Similarly, in some embodiments, the method according to the present disclosure further includes the step of e) subjecting the separated photopolymerizable composition to additional centrifugation to remove at least a portion of the dissolved gas or bubbles from the photopolymerizable composition.

[0051] In some embodiments, the method according to the present disclosure further includes, prior to step a), step f) selectively curing the initial photopolymerizable composition using a chemical beam to provide a three-dimensional object, as well as a fluid containing the photopolymerizable composition and contaminants. As described above, the initial photopolymerizable composition has not yet been subjected to a chemical beam. The selective curing process for forming the three-dimensional object (e.g., additive manufacturing) also generates one or more contaminants in the fluid. Suitable photopolymerizable compositions to be selectively cured are not particularly limited. One composition that may be useful in the method according to the present disclosure is described in the shared International Publication No. 2018 / 231583 (Hermann et al.). For example, such a photopolymerizable composition is It is a resin matrix, Polymerizable (meth)acrylates (multiple) that do not contain urethane, and Contains polymerizable urethane (meth)acrylate(plural), A resin matrix in which polymerizable (meth)acrylates (or multiple) that do not contain urethane are used in excess of polymerizable urethane (meth)acrylates (or multiple), A filler matrix, Nanoclusters (multiple clusters possible), and Optionally, preferably containing less than 8% by weight of fumed silica, Preferably, a filler matrix present in an amount of 5 to 45% by weight, It is an initiator system, Photoinitiators (multiple may be allowed), and It may also include an initiator system containing organic dyes (or more), The curable composition does not contain more than 5% by weight of a softening agent. Here, weight percent refers to weight percent relative to the total weight of the composition. The curable composition is curable at 23°C and 1 second. -1 At a shear rate of 150 Pa * It has a viscosity of less than s.

[0052] Further details regarding such photopolymerizable (e.g., curable) compositions are described in International Publication No. 2018 / 231583 (Hermann et al.).

[0053] Selective curing of (initial or separated) photopolymerizable compositions can be advantageously carried out via additive manufacturing, such as by using stereolithography (e.g., vat polymerization). Preferred additive manufacturing methods are discussed in more detail below with respect to a second aspect (i.e., a system).

[0054] In some embodiments, the method according to the present disclosure further includes the step of g) moving a three-dimensional object to generate a mass inertial force on an uncured photopolymerizable composition placed on the three-dimensional object, thereby forming a coating layer of the uncured photopolymerizable composition on the three-dimensional object, the mass inertial force being generated using a centrifuge, a shaker, or a mixer spinning along one or more axes. In some embodiments, the coating layer of the uncured photopolymerizable composition on the three-dimensional object (after the application of the mass inertial force) has a thickness of 20 micrometers or more, 25, 30, 35, 40, 45, or 50 micrometers or more; and 200 micrometers or less. In other embodiments, as much of the uncured photopolymerizable composition as possible is removed from at least one surface of the three-dimensional object using the mass inertial force (e.g., thereby cleaning the uncured photopolymerizable composition from the three-dimensional object). Preferred methods for generating mass inertial forces are described, for example, in the shared International Publication No. 2019 / 102304 (Kirchner et al.) and International Publication No. 2020 / 157598 (Chakraborty et al.), which are incorporated herein by reference in their entirety. For example, mass inertial forces may be generated using a centrifuge, a shaker, or a mixer that spins along one or more axes. In some embodiments, the motion of an object is rotation or spinning of the object. Thus, the mass inertial force can be a centrifugal force. One preferred mixer that spins along two or more axes is a dual asymmetric centrifugal mixer, such as the DAC400FVZ available from Flacktek (Landrum, SC). Dual asymmetric centrifugal mixers provide simultaneous biaxial spin that automatically changes the orientation of the object during spinning, which helps to extract the uncured composition from concave features of a three-dimensional object in a short time (e.g., 20 seconds, 15 seconds, or 10 seconds or less).

[0055] In selected embodiments, a mass inertia force may be advantageously applied to the same three-dimensional object in the insert that is subjected to centrifugal force in step c) of the method according to the present disclosure. Further optionally, the same centrifugal force can be used to separate contaminants from the photopolymerizable composition and to remove the uncured photopolymerizable composition from the three-dimensional object, for example, generally simultaneously. In some embodiments, the uncured photopolymerizable composition may be collected, for example, in an automated platform changer equipped with a liquid tank for collecting dripping uncured photopolymerizable composition when removing the three-dimensional object from the bulk of the uncured photopolymerizable composition, and in a container during the application of a mass inertia force (e.g., spin cleaning). Additional cleaning may also be performed to remove the uncured photopolymerizable composition from one or more outer or inner surfaces of the three-dimensional object, for example, using a solvent (e.g., water, alcohol, and / or a blend), compressed gas, or both.

[0056] If the fluid collection after the manufacture of a three-dimensional object is performed in a cleanroom atmosphere, further contamination of the collection source can be advantageously avoided. Furthermore, if the bulk of uncured photopolymerizable composition (e.g., remaining in the additive manufacturing fluid tank) contains part fragments, optionally, centrifugal force may be applied to the entire remaining contents of the fluid tank to separate at least the part fragments from the photopolymerizable composition, allowing for the continuous manufacture of three-dimensional objects from the photopolymerizable composition. Some scenarios in which bulk reuse of photopolymerizable composition is useful include, for example, when a print job fails and broken parts are present in the photopolymerizable composition, or after the (e.g., continuous) printing of many parts.

[0057] Post-treatment of the formed three-dimensional object is optionally performed, including, for example, post-curing, cleaning, or both. In some embodiments, the three-dimensional object contains unreacted photopolymerizable components, and the method further includes the step of h) curing the unreacted photopolymerizable components by subjecting the three-dimensional object to at least one of chemical radiation or heat. Exposure to chemical radiation can be performed by any convenient radiation source, generally ultraviolet radiation, visible radiation, and / or electron beam radiation, for a time ranging from about 1 minute to over 60 minutes. Heating is generally performed in an inert atmosphere at a temperature ranging from about 50 to 250°C for a time ranging from about 10 to over 60 minutes. So-called post-curing ovens, which combine ultraviolet and thermal energy, are particularly suitable for use in the post-curing process. Generally, post-curing improves the mechanical properties and stability of the three-dimensional object compared to the same three-dimensional object that has not been post-cured.

[0058] In some embodiments, the method according to the present disclosure further includes the step of i) analyzing the separated photopolymerizable composition for at least one of homogeneity or photoinitiator content. In some embodiments, homogeneity is analyzed by at least one of measuring the density of multiple samples of the separated photopolymerizable composition, measuring the color, or measuring the filler content. In some embodiments, homogeneity is analyzed by preparing a three-dimensional object from multiple samples of the separated photopolymerizable composition, subsequently testing its mechanical properties (e.g., tensile strength) and measuring its physical dimensions. Typically, a test bar having a shape (e.g., dogbone) according to a standard mechanical properties test method is formed either by additive manufacturing of the separated photopolymerizable composition sample, or by using a mold and casting the separated photopolymerizable composition sample. Testing of mechanical properties may indicate whether the photoinitiator concentration has decreased from the initial photopolymerizable composition, or a lack of homogeneity. If the physical dimensions of the object are smaller or larger than designed, the separated photopolymerizable composition may be under-cured or over-cured, respectively, and fail to meet the homogeneity requirement. Typically, for suitability in additive manufacturing, a photopolymerizable composition must be stable against significant separation of its components, at least on the timescale required to complete a printing job. Optionally, the photopolymerizable composition can be extracted with a solvent to measure its particulate filler content, preferably by testing several sections of the photopolymerizable composition to determine whether the particulate filler content is substantially the same throughout, thereby demonstrating the homogeneity of the photopolymerizable composition. Suitable methods for analyzing the photoinitiator content include infrared (IR) spectroscopy and high-pressure liquid chromatography (HPLC), respectively.

[0059] In some embodiments, the method according to the present disclosure further includes the steps of j) placing at least a portion of the separated photopolymerizable composition in an additive manufacturing apparatus, and k) selectively curing the separated photopolymerizable composition in the additive manufacturing apparatus using a chemical beam to form a three-dimensional object. Furthermore, in some embodiments, the method according to the present disclosure further includes the step of l) blending at least a portion of the separated photopolymerizable composition with a certain volume of initial photopolymerizable composition before step j) or step k). In at least certain embodiments, the separated photopolymerizable composition is clean enough to be used alone in place of unused (e.g., initial) photopolymerizable composition, or in the same batch as unused (e.g., initial) photopolymerizable composition. Advantageously, such a process can be used in medical product processes by enabling recycling within a single batch and reusing the recycled photopolymerizable composition without actual material batch mixing. Also, as a matter of practicality, the photopolymerizable composition may only come into direct contact with some simple shape manufacturing parts, making it easily recyclable by separating the photopolymerizable composition from the parts and any contaminants.

[0060] In some embodiments, the method according to the present disclosure further includes at least one of the following steps: m) cleaning the sieve or replacing the sieve if the multiple openings of the sieve become clogged with contaminants. After at least one use, the sieve tends to become clogged with one or more contaminants and requires cleaning or replacement with a clean sieve. Furthermore, it may be useful to change to a sieve having different opening sizes. In selected embodiments, if the sieve is made of nylon, isopropanol is a suitable cleaning solvent for the sieve. Optionally, disposable sieves that are discarded after use may be used.

[0061] system In a second embodiment, a system is provided. The system is a) Additive manufacturing apparatus, b) Centrifugal separator, c) an insert configured to be inserted into a centrifuge, comprising a sieve defining a plurality of openings, each having a diameter of 10 to 200 micrometers.

[0062] The method for printing a three-dimensional object described herein may include forming an article from multiple layers of the photopolymerizable composition described herein by layering them one layer at a time. Furthermore, the layers of the material composition to be constructed may be deposited according to a computer-readable image of the three-dimensional object. In some or all embodiments, the photopolymerizable composition is deposited according to pre-selected computer-aided design (CAD) parameters (e.g., a data file).

[0063] Furthermore, it is understood that the methods for manufacturing three-dimensional objects described herein may include so-called "stereolithography / liquid-bath polymerization" 3D printing methods. Other techniques for three-dimensional manufacturing are known and may be suitably adapted for use in the applications described herein. More generally, a succession of three-dimensional manufacturing techniques are becoming available. All such techniques can be modified for use with the photopolymerizable compositions described herein, provided they provide manufacturing viscosity and resolution that meet the specified article properties. Manufacturing may be carried out using any of the manufacturing techniques described herein, either alone or in various combinations, using data representing a three-dimensional object, which may be reformatted or otherwise adapted as necessary to suit a particular printing technique or other manufacturing technique.

[0064] It is entirely possible to form three-dimensional objects from the photopolymerizable compositions described herein using vat polymerization (e.g., stereolithography). For example, in some cases, a method for printing a three-dimensional object includes holding the photopolymerizable composition described herein in a fluid state in a container, selectively applying energy to the photopolymerizable composition in the container to solidify at least a portion of the fluid layer of the photopolymerizable composition, thereby forming a hardened layer that defines the cross-section of the three-dimensional object. Furthermore, the method described herein may further include raising and lowering the hardened layer of the photopolymerizable composition to provide a new, i.e., second fluid layer of unhardened photopolymerizable composition to the surface of the fluid in the container, and subsequently selectively applying energy again to the photopolymerizable composition in the container to solidify at least a portion of the new, i.e., second fluid layer of the photopolymerizable composition, thereby forming a second hardened layer that defines the second cross-section of the three-dimensional object. Furthermore, by applying energy to solidify the photopolymerizable composition, the first and second cross-sections of a three-dimensional object can be bonded or adhered to each other in the z-direction (i.e., the construction direction corresponding to the direction of elevation described above). Furthermore, selectively applying energy to the photopolymerizable composition in the container may include applying chemical beams such as ultraviolet, visible, or electron beam radiation that have sufficient energy to cure the photopolymerizable composition. The method may also include planarizing a new layer of fluid of the photopolymerizable composition provided by raising and lowering the platform of an elevator. Such planarization can be performed in some cases by utilizing a wiper, roller, or recoater. Planarization corrects the thickness of one or more layers before curing the material by flattening the dispensed material to remove excess material and creating a uniformly smooth exposed or flat upward surface on the printer's support platform.

[0065] It should be further understood that the process described above can be repeated a selected number of times to provide a three-dimensional object. For example, in some cases, this process can be repeated "n" times. Furthermore, it is understood that one or more steps of the method described herein, such as the step of selectively applying energy to a layer of photopolymerizable composition, can be performed according to a computer-readable image of the three-dimensional object. Suitable stereolithography printers include the Viper Pro SLA, available from 3D Systems (Rock Hill, SC), and the Asiga PICO PLUS39, available from Asiga USA (Anaheim Hills, CA).

[0066] Referring to Figures 2A to 2D, an exemplary system is collectively shown, comprising: a) an additive manufacturing apparatus (Figure 2A); b) a centrifuge (Figure 2B); and c) an insert configured to be inserted into the centrifuge, the insert comprising a sieve defining a plurality of openings, each having a diameter of 10 to 200 micrometers (Figures 2C to 2D). Figures 2B, 2C, and 2D are described in detail above. The additive manufacturing apparatus, centrifuge, and insert of the system may be used in combination, for example, as described above with respect to the first embodiment.

[0067] Figure 2A shows a stereolithography apparatus ("SLA") which may be used in a system with, for example, the photopolymerizable compositions and methods described herein. Generally, the apparatus 200 may include a laser 202, an optical element 204, a steering mirror or lens 206, an elevator 208, and a platform 210 in a liquid tank 214 filled with a photopolymerizable composition 219. During operation, the laser 202 is guided through the wall 220 (e.g., floor) of the liquid tank 214 into the photopolymerizable composition, curing a section of the photopolymerizable composition 219 to form an article 217, after which the elevator 208 slightly raises the platform 210 and curing another section. Suitable stereolithography printers include the NextDent 5100 and Figure 4, both available from 3D Systems (Rock Hill, SC), and the Asiga PICO PLUS39, available from Asiga USA (Anaheim Hills, CA).

[0068] In some embodiments, vat polymerization by digital light processing ("DLP") uses a vessel for a curable polymer (e.g., a photopolymerizable composition). In DLP-based systems, a two-dimensional cross-section is projected onto the curable material to cure a desired section of an entire plane across the projected beam in one go. One suitable apparatus for use with photopolymerizable compositions is the Rapid Shape D40 II DLP 3D printer (Rapid Shape GmbH, Heimsheim, Germany). All such curable polymer systems, which may be adapted for use with the photopolymerizable compositions described herein, are intended to fall within the scope of "vat polymerization" or "stereolithography" when used herein. In certain embodiments, apparatus adapted for use in continuous mode, such as those commercially available from Carbon 3D, Inc. (Redwood City, CA), may be used, as described, for example, in U.S. Patents 9,205,601 and 9,360,757 (both by DeSimone et al.).

[0069] The insert, container, and one or more sieves are all as described in detail above with respect to the first embodiment.

[0070] Various embodiments are provided, including methods and systems for removing contaminants from photopolymerizable compositions.

[0071] In a first embodiment, the present disclosure provides a method, the method comprising: a) obtaining an insert comprising a sieve defining a plurality of openings, each having a diameter of 10 to 200 micrometers; b) placing a certain volume of fluid comprising a photopolymerizable composition and contaminants into the insert; and c) separating the contaminants from at least a portion of the photopolymerizable composition by applying centrifugal force to the volume of fluid to retain the contaminants in the insert and allowing at least a portion of the photopolymerizable composition to pass through the sieve of the insert, thereby providing a separated photopolymerizable composition.

[0072] In a second embodiment, the disclosure provides a method of the first embodiment, further comprising the step of placing the insert in a centrifuge either before or after placing a certain volume of fluid in the insert.

[0073] In a third embodiment, the disclosure provides the method of the first embodiment, wherein at least a portion of the insert is placed in a container configured to fit into a centrifuge, and a portion of the photopolymerizable composition passing through the sieve of the insert is collected in the container.

[0074] In a fourth embodiment, the disclosure provides a method of the third embodiment, further comprising the step of balancing the centrifuge by placing a certain volume of fluid into a second insert of the centrifuge, which is located opposite to the insert of step b), prior to step c).

[0075] In a fifth embodiment, the disclosure provides a method according to any one of the first to third embodiments, wherein the contaminant comprises at least one of oligomers, polymers, dust particles, dust, a plurality of cured voxels formed from a photopolymerizable composition, or a component formed from a polymerization product of a photopolymerizable composition.

[0076] In the sixth embodiment, the disclosure provides a method according to any one of the first to fifth embodiments, wherein the photopolymerizable composition exhibits shear-reducing behavior.

[0077] In the seventh embodiment, the disclosure provides a method according to any one of the first to sixth embodiments, wherein the separated photopolymerizable composition further comprises a particulate filler.

[0078] In the eighth embodiment, the disclosure provides a method of the seventh embodiment, further comprising the step of d) subjecting the separated photopolymerizable composition to homogenization.

[0079] In the ninth embodiment, the disclosure provides a method according to the eighth embodiment, wherein homogenization is carried out under reduced pressure.

[0080] In the tenth embodiment, the disclosure provides a method according to any one of the first to ninth embodiments, comprising the step of subjecting the separated photopolymerizable composition to homogenization using a kneader or mixer.

[0081] In the eleventh embodiment, the disclosure provides a method according to any one of the first to tenth embodiments, wherein step c) is carried out at ambient pressure.

[0082] In a twelfth embodiment, the disclosure provides a method according to any one of the first to eleventh embodiments, wherein the plurality of openings of the sieve include circular, elliptical, quadrilateral, triangular, or star-shaped.

[0083] In the thirteenth embodiment, the disclosure provides a method according to any one of the first to twelfth embodiments, wherein each of the multiple openings of the sieve has a diameter of 20 micrometers or more, 30 micrometers or more, 40 micrometers or more, 50 micrometers or more, or 60 micrometers or more; and a diameter of 100 micrometers or less, 90 micrometers or less, or 80 micrometers or less.

[0084] In a fourteenth embodiment, the disclosure provides a method according to any one of the first to thirteenth embodiments, wherein the sieve is a first sieve, and the insert further includes a second sieve positioned adjacent to the first sieve, the second sieve defining a plurality of openings, each having a diameter smaller than a plurality of openings of the first sieve.

[0085] In the 15th embodiment, the disclosure provides a method according to any one of the first to 14 embodiments, wherein in step c), the fluid is subjected to a centrifugal force greater than 1G.

[0086] In the sixteenth embodiment, the disclosure provides a method according to any one of the first to fifteenth embodiments, further comprising the step of e) subjecting the separated photopolymerizable composition to additional centrifugation to remove at least a portion of the dissolved gas or bubbles from the photopolymerizable composition.

[0087] In the 17th embodiment, the present disclosure provides a method according to any one of the first to 16 embodiments, further comprising the step of selectively curing the initial photopolymerizable composition using a chemical beam before step a) to provide a three-dimensional object, as well as a fluid containing the photopolymerizable composition and contaminants.

[0088] In the 18th embodiment, the present disclosure further includes the step of g) moving a three-dimensional object to generate a mass inertial force in a portion of a fluid placed on the three-dimensional object, wherein the mass inertial force is generated using a centrifuge, shaker, or mixer rotating along one or more axes, the method of the 17th embodiment.

[0089] In the 19th embodiment, the disclosure provides the method according to the 18th embodiment, wherein generating a mass inertial force forms a coating layer of an uncured photopolymerizable composition on a three-dimensional object, the coating layer having a thickness of 20 micrometers or more, 30 micrometers or more, 40 micrometers or more, or 50 micrometers or more.

[0090] In the 20th embodiment, the Disclosure provides a method according to any one of the 17th to 19th embodiments, wherein the three-dimensional object comprises an unreacted photopolymerizable component, and the Method further comprises the step of h) subjecting the three-dimensional object to at least one of chemical rays or heat to cure the unreacted photopolymerizable component.

[0091] In the 21st embodiment, the disclosure provides a method according to any one of the first to 20 embodiments, further comprising the step of i) analyzing the separated photopolymerizable composition for at least one of homogeneity or photoinitiator content.

[0092] In the 22nd embodiment, the disclosure provides a method according to the 21st embodiment, wherein homogeneity is analyzed by measuring the density of a three-dimensional object formed from a separated photopolymerizable composition, measuring its color, measuring its mechanical properties and / or physical dimensions, or measuring the filler content of a plurality of samples of the separated photopolymerizable composition.

[0093] In the 23rd embodiment, the disclosure provides a method according to the 21st or 22nd embodiment, wherein the photoinitiator content is analyzed by at least one of infrared (IR) spectroscopy or high-pressure liquid chromatography (HPLC).

[0094] In the 24th embodiment, the disclosure provides a method according to any one of the first to 23 embodiments, further comprising the steps of j) placing at least a portion of a separated photopolymerizable composition in an additive manufacturing apparatus, and k) selectively curing the separated photopolymerizable composition in the additive manufacturing apparatus using a chemical beam to form a three-dimensional object.

[0095] In a 25th embodiment, the disclosure provides a method of the 24th embodiment, further comprising the step of blending at least a portion of the separated photopolymerizable composition with a certain volume of the initial photopolymerizable composition, prior to step j) or step k).

[0096] In the 26th embodiment, the disclosure provides a method according to any one of the first to 25 embodiments, further comprising the step of (m) cleaning the sieve or replacing the sieve if any of the openings of the sieve become clogged with contaminants.

[0097] In a 27th embodiment, the present disclosure provides a system comprising: a) an additive manufacturing apparatus; b) a centrifuge; and c) an insert configured to be inserted into the centrifuge. The insert includes a sieve defining a plurality of openings, each having a diameter of 10 to 200 micrometers.

[0098] In a 28th embodiment, the disclosure provides the system according to the 27th embodiment, further comprising a container configured to be inserted into a centrifuge, wherein at least a portion of the insert is sized to fit into the container.

[0099] In the 29th embodiment, the disclosure provides the system according to the 28th embodiment, wherein the container has a volume greater than the volume of at least a portion of an insert sized to fit into the container.

[0100] In the 30th embodiment, the disclosure provides a system according to any one of the 27th to 29th embodiments, wherein the plurality of openings of the sieve include circular, elliptical, quadrilateral, triangular, or star-shaped.

[0101] In the 31st embodiment, the disclosure provides a system according to any one of the 27th to 30th embodiments, wherein each of the multiple openings of the sieve has a diameter of 20 micrometers or more, 30 micrometers or more, 40 micrometers or more, 50 micrometers or more, or 60 micrometers or more; and a diameter of 100 micrometers or less, 90 micrometers or less, or 80 micrometers or less.

[0102] In the 32nd embodiment, the disclosure provides a system according to any one of the 27th to 31st embodiments, wherein the sieve is a first sieve, and the insert further includes a second sieve positioned adjacent to the first sieve, the second sieve defining a plurality of openings, each having a diameter smaller than a plurality of openings of the first sieve.

[0103] In the 33rd embodiment, the disclosure provides a system according to any one of the 27th to 32nd embodiments, further comprising a removable sieve stabilizer.

[0104] In the 34th embodiment, the disclosure provides a system according to any one of the 27th to 33rd embodiments, wherein the centrifuge includes a sensor that measures imbalance and terminates centrifugal force if the imbalance exceeds a threshold amount.

[0105] The following embodiments are described to illustrate further features and embodiments of the present invention. Unless otherwise specified, all parts are measured in parts by weight. [Examples]

[0106] The objects and advantages of the present invention are further illustrated by the following examples, but the specific materials and their amounts, as well as other conditions and details described in these examples, should not be construed as unduly limiting the present invention. These examples are for illustrative purposes only and are not intended to limit the scope of the appended claims. Unless otherwise stated or clearly apparent from the context, all parts, percentages, ratios, etc. in the examples and elsewhere in this specification are on a weight basis.

[0107]

Table 1

[0108] Test method Viscosity The viscosity was measured using a Physica Rheometer MCR 301 device with a plate / plate system (diameter 15 mm) and a slit of 0.2 mm. A constant shear rate of 100 s -1 was applied for 120 seconds (s), and then the shear rate was decreased from 100 s -1 to 0.001 s -1 by decreasing it (exponentially decreasing 60 times) to perform the preshear step. Finally, the viscosity values (Pa·s) were recorded at 23°C by increasing them exponentially 60 times from 0.001 s -1 starting and up to 1.000 s -1 for each shear rate. For each shear rate, data were collected typically after using a waiting time of 5 seconds. The above measurement method essentially corresponds to DIN 53018-1.

[0109] Manufacture of inserts The inserts were designed via computer-aided design (CAD), and the parts of the assembly (excluding the sieve cloth) were 3D printed from polylactic acid (PLA) using a fused deposition modeling (FDM) printer (Anycubic Predator).

[0110] Preparation of the initial photopolymerizable composition Example 1 Compositions having the formulations shown in Table 2 were prepared. This corresponds to Example 6 of International Publication No. 2018 / 231583 (Herrmann et al.). The amounts of the components are given in weight percentage (%):

[0111] [Table 2]

[0112] The viscosity of the initial photopolymerizable composition of Example 1, measured using the viscosity test method described above, yielded the following results.

[0113] [Table 3]

[0114] printing Using a Rapid Shape D90 Triple Fine SLA Printer (Rapid Shape, Heimsheim, Germany) equipped with an automatic platform changer, 1920 tooth crowns with supporting structures were fabricated in 3D using the initial photopolymerizable composition identified in Example 1 above. The printing parameters were as follows: 100 W / m² 2 Light energy, pixel size of 35 micrometers, layer height of 50 micrometers, exposure time of 1 second.

[0115] fluid collection Each of the eight platform changer slots of the Rapid Shape D90 Triple Fine SLA Printer had a sheet of coated paper (3M ESPE Mixing Pad, 3M Oral Care, Seefeld, Germany) to collect uncured photopolymerizable composition dripping from the build plate after printing. Following the print job, the dripped material in the platform changer was collected from the coated paper into a collection container using a silicone scraper.

[0116] Insert Assembly A sieve cloth piece (63 micrometer mesh size, approximately 120 x 120 mm) was cut from the roll / bulk with scissors. The first sieve cloth holder was placed inside the insert body. Next, the sieve cloth piece was placed on top of the sieve cloth holder. The second sieve cloth holder was placed on top of the sieve. The top of the insert (e.g., a removable sieve stabilizer) was attached to the top of the second sieve cloth holder. Next, a container for collecting the separated photopolymerizable composition (e.g., recycled material) was attached to the bottom side of the insert body. Then, 100 g of fluid (e.g., contaminated material) was added to the top of the insert. The entire assembly containing the fluid was then weighed on a laboratory scale. The second insert was prepared in the same manner as described above. To avoid imbalance during centrifugation, fluid was added to the second insert until the two assemblies had the same weight. The assemblies were then placed in centrifugation cups and positioned opposite each other in the centrifuge.

[0117] Centrifugal separation A Sigma 6-15 lab centrifuge (Sigma Laborzentrifugen GmbH, Osterode, Germany) was used for the centrifugation step. The equilibrium assembly in the centrifuge was centrifuged at 350 rpm for 2 minutes. After centrifugation, the photopolymerizable composition from the top of the insert passed through a sieve cloth by centrifugal force and into a container (e.g., a speed mixer cup) for the separated photopolymerizable composition (e.g., recycled material). The container containing the separated photopolymerizable composition was then capped and labeled.

[0118] Preparation for the next centrifugation run All components of the insert assembly shown in Figure 5 were disassembled and cleaned with alcohol. The used sieve cloth, including the filter cake, could be discarded or cleaned with ethanol and reused.

[0119] Evaluation of filter cakes To inspect the filter cake, a sieve cloth containing the filter cake cloth was immersed in isopropyl alcohol (IPA) to wash away any residual resin. After drying the filter cake in a fume hood, the solids in the filter cake were examined under a microscope. As described above with respect to Figure 6, typical contents, namely small broken pieces (e.g., fragments of the support geometry), semi-cured residue, and dust, were observed in the filter cake.

[0120] All disclosures of patents, patent documents, and publications referenced herein are incorporated by reference as if each were incorporated individually. In the event of any inconsistency or conflict between the statements herein and the disclosures of any of the documents incorporated herein by reference, the statements herein shall prevail. Those skilled in the art will see various modifications and changes to this disclosure that do not deviate from the scope and intent of this disclosure. It should be understood that this disclosure is not intended to be unduly limited by the exemplary embodiments and examples described herein, and that such embodiments and examples are presented only as examples within the scope of this disclosure, which is intended to be limited only by the claims described herein as follows.

Claims

1. a) obtaining an insert including a sieve defining a plurality of openings, each opening having a diameter of 10 to 200 micrometers; b) disposing a volume of fluid within the insert, the fluid including a photopolymerizable composition and a contaminant; c) separating the contaminants from at least a portion of the photopolymerizable composition by applying centrifugal force to the volume of fluid to retain the contaminants within the insert and forcing at least a portion of the photopolymerizable composition through the sieve of the insert to provide a separated photopolymerizable composition.

2. The method of claim 1 , wherein at least a portion of the insert is placed in a container configured to fit into a centrifuge, and the portion of the photopolymerizable composition that passes through the sieve of the insert is collected in the container.

3. 3. The method of claim 1 or 2, wherein the contaminants include at least one of an oligomer, a polymer, a dust particle, dirt, a plurality of cured voxels formed from the photopolymerizable composition, or a part formed of a polymerization product of the photopolymerizable composition.

4. 4. The method of any one of claims 1 to 3, wherein the separated photopolymerizable composition further comprises a particulate filler, and the method further comprises the step of: d) subjecting the separated photopolymerizable composition to homogenization.

5. 5. The method of claim 4, wherein the homogenization is carried out under reduced pressure.

6. The method of any one of claims 1 to 5, wherein step c) is carried out at ambient pressure.

7. 7. The method of any one of claims 1 to 6, wherein the sieve is a first sieve and the insert further comprises a second sieve positioned adjacent to the first sieve, the second sieve defining a plurality of openings each having a diameter smaller than the plurality of openings of the first sieve.

8. 8. The method of any one of claims 1 to 7, further comprising the step of: e) subjecting the separated photopolymerizable composition to an additional centrifugation to remove at least a portion of dissolved gas or bubbles from the photopolymerizable composition.

9. 9. The method of any one of claims 1 to 8, further comprising, prior to step a), the step of: f) selectively curing the initial photopolymerizable composition using actinic radiation to provide a three-dimensional object and the fluid comprising the photopolymerizable composition and the contaminant.

10. 10. The method of claim 9, further comprising: g) moving the three-dimensional object, thereby generating a mass inertia force on a portion of the fluid disposed on the three-dimensional object, wherein the mass inertia force is generated using a centrifuge, a shaker, or a mixer that rotates along one or more axes.

11. The method of any one of claims 1 to 10, further comprising the step of: i) analyzing the separated photopolymerizable composition for at least one of homogeneity or photoinitiator content.

12. 12. The method of any one of claims 1 to 11, further comprising: j) placing at least a portion of the separated photopolymerizable composition in an additive manufacturing apparatus; and k) selectively curing the separated photopolymerizable composition in the additive manufacturing apparatus using actinic radiation to form a three-dimensional object.

13. 13. The method of claim 12, further comprising, prior to step j) or step k), the step of: l) blending at least a portion of the separated photopolymerizable composition with a volume of initial photopolymerizable composition.

14. a) an additive manufacturing device; b) a centrifuge; c) an insert configured to be inserted into the centrifuge, the insert including a sieve defining a plurality of openings, each opening having a diameter of 10 to 200 micrometers; A system comprising:

15. 15. The system of claim 14, wherein the sieve is a first sieve and the insert further includes a second sieve positioned adjacent to the first sieve, the second sieve defining a plurality of openings each having a diameter smaller than the plurality of openings of the first sieve.

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