Formulations usable in additive manufacturing of three-dimensional objects

Abstract

Modeling material formulations usable for additive manufacturing of a three-dimensional object, additive manufacturing processes employing same and three-dimensional objects obtained thereby, are provided. The modeling material formulations comprise at least one mono-functional (meth)acrylate featuring, when hardened, Tg higher than 80, or higher than 100 °C; at least one multi-functional urethane (meth) acrylate featuring, when hardened, Tg higher than 80, or higher than 100 °C; at least one multi-functional polyether (meth)acrylate material featuring, when hardened, Tg lower than 20, or lower than 0, °C, optionally featuring MW higher than 500 grams / mol; and at least one acrylate material represented by Formula I as defined in the instant specification.

Description

[0001] FORMULATIONS USABLE IN ADDITIVE MANUFACTURING OF THREE-DIMENSIONAL OBJECTS

[0002] RELATED APPLICATION / S

[0003] This application claims the benefit of priority of US Provisional Patent Application No. 63 / 720,777 filed on November 15, 2024, the contents of which are incorporated herein by reference in their entirety.

[0004] FIELD AND BACKGROUND OF THE INVENTION

[0005] The present invention, in some embodiments thereof, relates to additive manufacturing and, more particularly, but not exclusively, to formulations usable in additive manufacturing of three-dimensional objects featuring improved toughness and to additive manufacturing processes employing same.

[0006] Additive manufacturing (AM) is a technology enabling fabrication of arbitrarily shaped structures directly from computer data via additive formation steps. The basic operation of any AM system consists of slicing a three-dimensional computer model into thin cross sections, translating the result into two-dimensional position data and feeding the data to control equipment which fabricates a three-dimensional structure in a layer-wise manner.

[0007] Additive manufacturing entails many different approaches to the method of fabrication, including three-dimensional (3D) printing such as 3D inkjet printing, electron beam melting, stereolithography, digital light processing (DLP), selective laser sintering, laminated object manufacturing, fused deposition modeling and others.

[0008] Some 3D printing processes, for example, 3D inkjet printing, are being performed by a layer-by-layer inkjet deposition of building materials. Thus, a building material is dispensed from a dispensing head having a set of nozzles to deposit layers on a receiving medium. Depending on the building material, the layers may then be cured or solidified. Curing may be by exposure to a suitable condition, and optionally by using a suitable device.

[0009] The building material includes an uncured model material (also referred to as “uncured modeling material” or “modeling material formulation”), which is selectively dispensed to produce the desired object, and may also include an uncured support material (also referred to as "uncured supporting material” or “support material formulation”) which provides temporary support to specific regions of the object during building and assures adequate vertical placement of subsequent object layers. The supporting structure is configured to be removed after the 3D-printing is completed. In some known inkjet printing systems, the uncured model material is a photopolymerizable or photocurable material that is cured, hardened or solidified upon exposure to irradiation, typically to ultraviolet (UV) light, after it is jetted. The uncured model material may be a photopolymerizable material formulation that has a composition which, after curing, gives a solid material with mechanical properties that permit the building and handling of the three-dimensional object being built. The modeling material formulation typically includes a reactive (curable) component and a photo-initiator. The photo-initiator may enable at least partial solidification (hardening) of the uncured support material by curing with the same UV light applied to form the model material. The solidified material may be rigid, or may have elastic properties.

[0010] The support material is formulated to permit fast and easy cleaning of the object from its support. The support material may be a polymer, which is water-soluble and / or capable of swelling and / or breaking down upon exposure to a liquid solution, e.g. water, alkaline or acidic water solution. The support material formulation may also include a reactive (curable) component and a photo-initiator.

[0011] In order to be compatible with most of the commercially-available print heads utilized in a 3D inkjet printing system, the uncured building materials should preferably feature the following characteristics: a relatively low viscosity (e.g., Brookfield Viscosity of up to 300 centipoises (cps; or mPa- second), or up to 150 cps (mPa- second), or up to 75 cps (mPa- second), or up to 35 cps (mPa- second), preferably from 8 to 25 cps (mPa- second)) at the working (e.g., jetting) temperature; Surface tension of from about 25 to about 55 Dyne / cm, preferably from about 25 to about 40 Dyne / cm; and a Newtonian liquid behavior and high reactivity to a selected curing condition, to enable fast solidification of the jetted layer upon exposure to a curing condition, of no more than 1 minute, preferably no more than 20 seconds.

[0012] Various three-dimensional printing techniques exist and are disclosed in, e.g., U.S. Patent Nos. 6,259,962, 6,569,373, 6,658,314, 6,850,334, 6,863,859, 7,183,335, 7,209,797, 7,225,045, 7,300,619, 7,500,846, 7,991,498 and 9,031,680 and U.S. Published Application No. 20160339643, all by the present Assignee, and being hereby incorporated by reference in their entirety.

[0013] Several additive manufacturing processes, including three-dimensional inkjet printing, allow additive formation of objects using more than one modeling material, also referred to as “multi-material” AM processes. For example, U.S. Patent Application having Publication No.

[0014] 2010 / 0191360, by the present Assignee, discloses a system which comprises a solid freeform fabrication apparatus having a plurality of print heads, a building material supply apparatus configured to supply a plurality of building materials to the fabrication apparatus, and a control unit configured for controlling the fabrication and supply apparatus. The system has several operation modes. In one mode, all print heads operate during a single building scan cycle of the fabrication apparatus. In another mode, one or more of the print heads is not operative during a single building scan cycle or part thereof.

[0015] In a 3D inkjet printing process such as PolyJet™ (Stratasys® Ltd., Israel), the building material is selectively jetted from one or more inkjet print heads and / or nozzles and deposited onto a fabrication tray in consecutive layers according to a pre-determined configuration as defined by a software file.

[0016] The PolyJet™ technology allows control over the position and composition of each voxel (volume pixel), which affords enormous design versatility and digital programming of multimaterial structures. Other advantages of the Poly Jet™ technology are the very high printing resolution, up to 14 pm layer height, and the ability to print multiple materials simultaneously, in a single object. This multi-material 3D printing process often serves for fabrication of complex parts and structures that are comprised of elements having different stiffness, performance, color or transparency. New ranges of materials, programmed at the voxel level, can be created by the PolyJet™ printing process, using only few starting materials.

[0017] International Patent Application Publication No. WO 2013 / 128452, by the present Assignee, discloses a multi-material approach which involves separate jetting of two components of a cationic polymerizable system and / or a radical polymerizable system, which intermix on the printing tray, leading to a polymerization reaction similar to pre-mixing of the two components before jetting, while preventing their early polymerization on the inkjet printhead nozzle plate.

[0018] Current PolyJet™ technology offers the capability to use a range of curable (e.g., polymerizable) materials that provide polymeric materials featuring a variety of properties, ranging, for example, from stiff and hard materials (e.g., curable formulations marketed as the Vero™ Family materials) to soft and flexible materials (e.g., curable formulations marketed as the Tango™ and Agilus™ families), and including also objects made using Digital ABS, which contain a multi-material structure made of two starting materials (e.g., RGD515™ & RGD535 / 531™), and simulate properties of engineering plastic. Most of the currently practiced PolyJet™ materials are curable materials which harden or solidify upon exposure to radiation, mostly UV radiation and / or heat, with the most practiced materials being acrylic -based materials.

[0019] The hardened modeling material which forms the final object should ideally exhibit a heat deflection temperature (HDT) which is higher than room temperature, in order to assure its usability. Desirably, the hardened modeling material exhibits an HDT of at least 35 °C. For an object to be stable at variable conditions, a higher HDT is known to be desirable. In most cases, it is also desirable that the object exhibits relatively high toughness, typically high Izod Notched impact (also known and referred to herein and in the art as “Impact Resistance”), e.g., higher than 50 or higher than 60 J / m. However, typically there is an inverse effect between the HDT and the impact resistance of the hardened material, and achieving high toughness of inkjet-printed hardened materials has been challenging.

[0020] SUMMARY OF THE INVENTION

[0021] According to an aspect of some embodiments of the present invention there is provided a modeling material formulation usable for additive manufacturing of a three-dimensional object, the modeling material formulation comprising:

[0022] at least one mono-functional (meth) acrylate featuring, when hardened, Tg higher than 80, or higher than 100 °C (Component A);

[0023] at least one multi-functional urethane (meth) acrylate featuring, when hardened, Tg higher than 80, or higher than 100 °C (Component D);

[0024] at least one multi-functional polyether (meth) acrylate material featuring, when hardened, Tg lower than 20, or lower than 0, °C, optionally featuring MW higher than 500 grams / mol (Component E); and

[0025] at least one acrylate material represented by Formula I (Component C):

[0026]

[0027] Formula I

[0028] wherein:

[0029] Ri and R2 are each independently hydrogen or alkyl (e.g., a lower alkyl of 1-6 or 1-4 carbon atoms);

[0030] Y is selected from O, S, NR3, and CR4R5, wherein R3, R4 and R5 are each independently selected from hydrogen and alkyl (e.g., a lower alkyl of 1-6 or 1-4 carbon atoms); and

[0031] Xi and X2 are each independently a substituted or unsubstituted alkylene of 1-4 carbon atoms in length, such that the total number of atoms of a backbone chain formed of Xi, Y and X2 is no more than 6. According to some embodiments of any of the embodiments described herein, Y is O, the compound being an a-(unsaturated alkoxyalkyl) acrylate.

[0032] According to some embodiments of any of the embodiments described herein, the total number of carbon atoms in Xi and X2 is no more than 5.

[0033] According to some embodiments of any of the embodiments described herein, Xi and X2 are each methylene (e.g., unsubstituted methylene).

[0034] According to some embodiments of any of the embodiments described herein, Ri is alkyl (e.g., methyl).

[0035] According to some embodiments of any of the embodiments described herein, R2 is hydrogen.

[0036] According to some embodiments of any of the embodiments described herein, Component C is or comprises methyl 2-((allyloxy)methyl)acrylate.

[0037] According to some embodiments of any of the embodiments described herein, an amount of Component C ranges from 15 to 25, preferably from 18 to 22, or s about 20, % by weight, of the total weight of the formulation.

[0038] According to some embodiments of any of the embodiments described herein, Component D is or comprises a multi-functional aliphatic (meth) acrylate featuring, when hardened, the indicated Tg.

[0039] According to some embodiments of any of the embodiments described herein, Component D is or comprises a di-functional urethane (meth) acrylate featuring, when hardened, the indicated Tg- According to some embodiments of any of the embodiments described herein, Component D is or comprises a di-functional aliphatic urethane (meth) acrylate featuring, when hardened, the indicated Tg.

[0040] According to some embodiments of any of the embodiments described herein, Component D is or comprises a multi-functional (e.g., di-functional) urethane methacrylate featuring, when hardened the indicated Tg.

[0041] According to some embodiments of any of the embodiments described herein, Component D is or comprises a multi-functional (e.g., di-functional) aliphatic urethane methacrylate featuring, when hardened the indicated Tg.

[0042] According to some embodiments of any of the embodiments described herein, Component D features, when hardened, Tg of at least 100, or at least 120, °C. According to some embodiments of any of the embodiments described herein, Component D is or comprises a di-functional aliphatic methacrylate featuring, when hardened, Tg of at least 100, or at least 120, °C.

[0043] According to some embodiments of any of the embodiments described herein, an amount of Component D is at least 10 % by weight, or ranges from 10 to 20, or from 10 to 15, % by weight, of the total weight of the formulation.

[0044] According to some embodiments of any of the embodiments described herein, Component E comprises a di-functional polyether (meth)acrylate.

[0045] According to some embodiments of any of the embodiments described herein, Component E is or comprises a multi-functional (e.g., di-functional) aliphatic (meth)acrylate featuring a poly(alkylene glycol moiety) (Component E2).

[0046] According to some embodiments of any of the embodiments described herein, the poly(alkylene glycol) moiety is selected from polypropylene glycol) moiety, poly(isopropylene glycol) moiety and poly(tetramethylene glycol) moiety.

[0047] According to some embodiments of any of the embodiments described herein, Component E is or comprises a di-functional aliphatic acrylate featuring a poly(alkylene glycol moiety) (e.g., a polypropylene glycol) moiety, poly(isopropylene glycol) moiety or a poly(tetramethylene glycol) moiety).

[0048] According to some embodiments of any of the embodiments described herein, Component E has a molecular weight in a range of from 500 to 2000, or from 500 to 1000, grams / mol.

[0049] According to some embodiments of any of the embodiments described herein, Component E is or comprises a multi-functional (e.g., di-functional) polyether urethane (meth) acrylate (Component El).

[0050] According to some embodiments of any of the embodiments described herein, Component El is a multi-functional (e.g., di-functional) polyether urethane (meth) acrylate featuring MW higher than 2,000 or higher than 3,000 grams / mol, or higher (Component El).

[0051] According to some embodiments of any of the embodiments described herein, Component El is a di-functional poly ether urethane acrylate.

[0052] According to some embodiments of any of the embodiments described herein, the multifunctional (e.g., di-functional) polyether urethane (meth)acrylate features a poly(alkylene glycol) moiety (e.g., a polypropylene glycol) moiety, poly(isopropylene glycol) moiety or a poly (tetramethylene glycol) moiety).

[0053] According to some embodiments of any of the embodiments described herein, Component E is or comprises Component El, which is a di-functional urethane acrylate featuring a poly(alkylene glycol) moiety (e.g., a polypropylene glycol) moiety, poly(isopropylene glycol) moiety or a poly(tetramethylene glycol) moiety) and having MW of at least 2,000, or at least 3,000 or at least 4,000 or at least 5,000 grams / mol.

[0054] According to some embodiments of any of the embodiments described herein, the poly (alkylene glycol) moiety is poly (isopropylene glycol).

[0055] According to some embodiments of any of the embodiments described herein, Component E is or comprises a multi-functional ethoxylated aromatic (meth)acrylate featuring at least 10 ethoxylated groups (Component E3).

[0056] According to some embodiments of any of the embodiments described herein, Component E3 is or comprises a di-functional ethoxylated aromatic (meth)acrylate featuring at least 10 ethoxylated groups.

[0057] According to some embodiments of any of the embodiments described herein, Component E comprises at least one of a multi-functional (e.g., di-functional) aliphatic (meth)acrylate featuring a poly(alkylene glycol moiety) (Component E2) and a multi-functional (e.g., di-functional) polyether urethane (meth)acrylate featuring MW higher than 2,000 or higher than 3,000 grams / mol (Component El).

[0058] According to some embodiments of any of the embodiments described herein, an amount of Component E ranges from 5 to 15, or from 5 to 12, % by weight, of the total weight of the formulation.

[0059] According to some embodiments of any of the embodiments described herein, Component A comprises at least one hydrophilic mono-functional (meth)acrylate featuring the indicated Tg (Component Al).

[0060] According to some embodiments of any of the embodiments described herein, Component A further comprises at least one hydrophobic mono-functional (meth)acrylate featuring the indicated Tg (Component A2).

[0061] According to some embodiments of any of the embodiments described herein, a total amount of Component Al and Component A2 ranges from 15 to 25, or from 20 to 25, % by weight of the total weight of the formulation.

[0062] According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises at least one mono-functional (meth) acrylate featuring, when hardened, Tg lower than 80 ° C, e.g., in a range of from 0 to 80, or from 0 to 50, °C (Component B). According to some embodiments of any of the embodiments described herein, Component B comprises a hydrophobic mono-functional (meth)acrylate featuring the indicated Tg (Component Bl).

[0063] According to some embodiments of any of the embodiments described herein, Component B comprises an epoxy-type mono-functional (meth)acrylate featuring the indicated Tg (Component B2).

[0064] According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises at least one multi-functional (meth)acrylate featuring, when hardened, Tg lower than 80, in a range of from 0 to 80, °C (Component F).

[0065] According to some embodiments of any of the embodiments described herein, Component F has a MW higher than 500, or higher than 1,000, or in range of from 1,000 to 2,000, grams / mol.

[0066] According to some embodiments of any of the embodiments described herein, Component F is a multi-functional (e.g., di-functional) urethane (meth)acrylate (e.g., acrylate) featuring, when hardened, the indicated Tg and having a MW lower than 2,000 grams / mol (Component F2).

[0067] According to some embodiments of any of the embodiments described herein, Component F2 features, when hardened, Tg lower than 50, or lower than 20, or in a range of from 0 to 50 or from 0 to 20, °C.

[0068] According to some embodiments of any of the embodiments described herein, an amount of Component F2, if present, ranges from 10 to 25 % by weight of the total weight of the formulation.

[0069] According to some embodiments of any of the embodiments described herein, Component F comprises at least one epoxy-type multi-functional (meth)acrylate (Component Fl).

[0070] According to some embodiments of any of the embodiments described herein, Component Fl is an epoxy-type multi-functional, preferably di-functional, acrylate.

[0071] According to some embodiments of any of the embodiments described herein, Component Fl features, when hardened, Tg higher than 50, or in a range of from 50 to 80, °C.

[0072] According to some embodiments of any of the embodiments described herein, Component Fl has MW in a range of from 1,000 to 2,000 grams / mol.

[0073] According to some embodiments of any of the embodiments described herein, an amount of Component Fl, if present, ranges from 5 to 20, or from 5 to 15, or from 10 to 15, % by weight, of the total weight of the formulation.

[0074] According to some embodiments of any of the embodiments described herein, Component F comprises at least one multi-functional (e.g., di-functional) urethane (meth) acrylate (e.g., acrylate) featuring, when hardened, the indicated Tg and having a MW higher than 2,000 grams / mol (Component F3).

[0075] According to some embodiments of any of the embodiments described herein, Component F3 features, when hardened, Tg in a range of from 0 to 50 °C.

[0076] According to some embodiments of any of the embodiments described herein, an amount of Component F3, if present, ranges from 1 to 10, or from 3 to 8, or from 3 to 5, % by weight, of the total weight of the formulation.

[0077] According to some embodiments of any of the embodiments described herein, Component F comprises a tri-functional urethane (meth) acrylate featuring, when hardened the indicated Tg and having MW higher than 2,000 grams / mol (Component F4).

[0078] According to some embodiments of any of the embodiments described herein, Component F4 features, when hardened, Tg in a range of from 0 to 50 °C.

[0079] According to some embodiments of any of the embodiments described herein, an amount of Component F4, if present, ranges from 1 to 5, or from 1 to 3, % by weight, of the total weight of the formulation.

[0080] According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises a dispersant (Component H).

[0081] According to some embodiments of any of the embodiments described herein, the dispersant comprises a dispersant that features curable groups (Component Hl).

[0082] According to some embodiments of any of the embodiments described herein, the dispersant is a multi-functional silicon polyester (meth)acrylate.

[0083] According to some embodiments of any of the embodiments described herein, an amount of Component Hl, if present, ranges from 0.5 to 1.5, or is about 1, % by weight of the total weight of the formulation.

[0084] According to some embodiments of any of the embodiments described herein, the dispersant comprises a non-curable dispersant (Component H2).

[0085] According to some embodiments of any of the embodiments described herein, an amount of Component H2 is at least 0.1, or ranges from 0.1 to 1, or from 0.1 to 0.5, % by weight of the total weight of the formulation.

[0086] According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises at least one photoinitiator (Component J).

[0087] According to some embodiments of any of the embodiments described herein, an amount of the photoinitiator ranges from 1 to 5, or from 1 to 3, % by weight, of the total weight of the formulation. According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises a polymerization inhibitor (Component I).

[0088] According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises a colorant (e.g., Component P).

[0089] According to some embodiments of any of the embodiments described herein, the colorant comprises a dye or a pigment.

[0090] According to some embodiments of any of the embodiments described herein, the colorant comprises a paste that comprises a dye or a pigment and mixture of mono-functional and multifunctional curable materials.

[0091] According to some embodiments of any of the embodiments described herein, modeling material formulation comprises at least:

[0092] Component A (e.g., Component Al), in a total amount of from 15 to 25 % by weight of the total weight of the formulation;

[0093] Component C, in a total amount of from 17 to 23, or of about 20, % by weight of the total weight of the formulation;

[0094] Component D, in a total amount of from 10 to 30, or from 10 to 20, % by weight, of the total weight of the formulation; and

[0095] Component E, in a total amount of from 5 to 15, % by weight of the total weight of the formulation.

[0096] According to some embodiments of any of the embodiments described herein, the modeling material formulation is a transparent formulation (which provides a transparent hardened material).

[0097] According to some embodiments of any of the embodiments described herein, the modeling material formulation is a colorless transparent formulation (which provides a colorless, clear, hardened material) or a colored transparent formulation, which further comprises a transparent dye or pigment.

[0098] According to some embodiments of any of the embodiments described herein, the modeling material formulation is an opaque formulation (which provides an opaque hardened material), which comprises an opaque pigment or dye.

[0099] According to some embodiments of any of the embodiments described herein, the modeling material formulation is a white opaque formulation (which provides a white opaque hardened material).

[0100] According to some embodiments of any of the embodiments described herein, the modeling material formulation is a colored (e.g., black) opaque formulation (which provides a colored (e.g., black) opaque hardened material). According to some embodiments of any of the embodiments described herein, the modeling material formulation features, when hardened, impact resistance (Izod XY notched impact resistance, as described and measured herein) of at least 40, or at least 50, J / m.

[0101] According to an aspect of some embodiments of the present invention there is provided a method of additive manufacturing a three-dimensional object, the method comprising sequentially forming a plurality of layers in a configured pattern corresponding to the shape of the object, thereby forming the object,

[0102] wherein the formation of each of at least a few of the layers comprises dispensing at least one formulation, and exposing the dispensed formulation to irradiation to thereby form a hardened modeling material,

[0103] wherein the at least one formulation is the modeling material formulation as defined herein in any of the respective embodiments and any combination thereof.

[0104] According to some embodiments of any of the embodiments described herein, the dispensing is further of an additional modeling material formulation.

[0105] According to some embodiments of any of the embodiments described herein, the modeling material formulation and the additional modeling material formulation form a digital material.

[0106] According to some embodiments of any of the embodiments described herein, the modeling material formulation and the additional modeling material formulation form a shelled structure.

[0107] According to some of any of the embodiments described herein, method further comprises, subsequent to exposing to the irradiation, exposing the object to photobleaching.

[0108] According to some embodiments of any of the embodiments described herein, the method is for manufacturing a three-dimensional object that comprises in at least a portion thereof a hardened material that exhibits impact resistance (Izod XY notched impact resistance, as defined and measured herein) of at least 40, or at least 50, J / m.

[0109] According to an aspect of some embodiments of the present invention there is provided a three-dimensional object obtained by the method as described herein in any of the respective embodiments.

[0110] According to some embodiments of any of the embodiments described herein, the three-dimensional object features in at least a portion thereof a hardened material that exhibits impact resistance (Izod XY notched impact resistance, as defined and measured herein) of at least 40, or at least 50, J / m, and further exhibits at least one of: HDT (ASTM D648) higher than 50 °C (e.g., 50-60 °C); Tensile Strength (ASTM D638) of at least 30, or of from about 30 to 50, MPa; Elongation at break (ASTM D638) of at least 25 %, or from about 25 to about 40, %; Flexural Strength (ASTM D790) of at least 40, or from about 40 to about 60, MPa; and Flexural Modulus (ASTM D790) of at least 1200, or from about 1200 to about 1800, MPa; , as these properties are described and defined herein.

[0111] According to some embodiments of any of the embodiments described herein, the three-dimensional object further exhibits, in at least a portion thereof, water absorption of a 60x60x1 mm cube lower than 10 %, or lower than 8 %, or 5 %, or lower than 3 %, or lower than 2, %, e.g., of 1-1.5 % (ASTM D 570-98).

[0112] According to some embodiments of any of the embodiments described herein, the three-dimensional object further exhibits, in at least a portion thereof, Izod un-notched ZX impact resistance higher than 100, preferably higher than 120 (e.g., 120-220) J / m.

[0113] According to some embodiments of any of the embodiments described herein, the three-dimensional object further exhibits, in at least a portion thereof, Minimal Creep (at 70 % humidity and 40 °C), as defined herein.

[0114] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0115] Implementation of the method and / or system of embodiments of the invention can involve performing or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of embodiments of the method and / or system of the invention, several selected tasks could be implemented by hardware, by software or by firmware or by a combination thereof using an operating system.

[0116] For example, hardware for performing selected tasks according to embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to exemplary embodiments of method and / or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes a volatile memory for storing instructions and / or data and / or a non-volatile storage, for example, a magnetic hard-disk and / or removable media, for storing instructions and / or data. Optionally, a network connection is provided as well. A display and / or a user input device such as a keyboard or mouse are optionally provided as well.

[0117] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0118] Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

[0119] In the drawings:

[0120] FIGs. 1A-D are schematic illustrations of an additive manufacturing system according to some embodiments of the invention;

[0121] FIGs. 2A-2C are schematic illustrations of printing heads according to some embodiments of the present invention;

[0122] FIGs. 3A and 3B are schematic illustrations demonstrating coordinate transformations according to some embodiments of the present invention;

[0123] FIG. 4 presents photographs of exemplary objects obtained using exemplary formulations according to some of the present embodiments;

[0124] FIG. 5 presents data obtained in studies conducted for evaluating an effect of various further treatment protocols on exemplary objects printed using an exemplary transparent formulation according to some embodiments of the present invention; and

[0125] FIGs. 6A-F are schematic illustrations of shelled structures, according to some embodiments of the present invention.

[0126] DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

[0127] The present invention, in some embodiments thereof, relates to additive manufacturing and, more particularly, but not exclusively, to formulations usable in additive manufacturing of three-dimensional objects featuring improved toughness and to additive manufacturing processes employing same.

[0128] Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and / or methods set forth in the following description and / or illustrated in the drawings and / or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

[0129] The present inventors have designed and successfully practiced new modeling material formulations which are usable in additive manufacturing of a three-dimensional object featuring improved properties, particularly improved impact resistance as described herein.

[0130] More specifically, the present inventors have designed modeling material formulations that comprise a curable material that impart to the hardened material improved toughness, such as, for example, a material of the a-(unsaturated alkoxyalkyljacrylate family and similar, structurally related, compounds that are represented by Formula I as described herein, while combining with this material mono-functional and multi-functional materials that allow using the formulations in 3D-inkjet printing, while meeting the process requirements and while providing hardened materials that feature improved impact resistance.

[0131] Embodiments of the present invention therefore relate to newly designed modeling material formulations and to methods and systems employing same in additive manufacturing of three-dimensional objects.

[0132] The method and system of the present embodiments manufacture three-dimensional objects based on computer object data in a layerwise manner by forming a plurality of layers in a configured pattern corresponding to the shape of the objects. The computer object data can be in any known format, including, without limitation, a Standard Tessellation Language (STL) or a StereoLithography Contour (SLC) format, an OBJ File format (OBJ), a 3D Manufacturing Format (3MF), Virtual Reality Modeling Language (VRML), Additive Manufacturing File (AMF) format, Drawing Exchange Format (DXF), Polygon File Format (PLY) or any other format suitable for Computer-Aided Design (CAD).

[0133] The term "object" as used herein refers to a whole object or a part thereof.

[0134] Each layer is formed by an additive manufacturing apparatus which scans a two-dimensional surface and patterns it. While scanning, the apparatus visits a plurality of target locations on the two-dimensional layer or surface, and decides, for each target location or a group of target locations, whether or not the target location or group of target locations is to be occupied by building material formulation, and which type of building material formulation is to be delivered thereto. The decision is made according to a computer image of the surface.

[0135] In preferred embodiments of the present invention the AM comprises three-dimensional printing, more preferably three-dimensional inkjet printing. In these embodiments a building material is dispensed from a printing head having one or more arrays of nozzles to deposit building material in layers on a supporting structure. The AM apparatus thus dispenses building material in target locations which are to be occupied and leaves other target locations void. The apparatus typically includes a plurality of arrays of nozzles, each of which can be configured to dispense a different building material. This is typically achieved by providing the printing head with a plurality of fluid channels are separated from each other such that there is no fluid communication therebetween, wherein each channel receives a different building material through a separate inlet and conveys it to a different array of nozzles.

[0136] Thus, different target locations can be occupied by different building material formulations. The types of building material formulations can be categorized into two major categories: modeling material formulation and support material formulation. The support material formulation serves as a supporting matrix or construction for supporting the object or object parts during the fabrication process and / or other purposes, e.g., providing hollow or porous objects. Support constructions may additionally include modeling material formulation elements, e.g. for further support strength.

[0137] The modeling material formulation is generally a composition which is formulated for use in additive manufacturing and which is able to form a three-dimensional object on its own, without having to be mixed or combined with any other substance.

[0138] The final three-dimensional object is made of the modeling material formulation or a combination of modeling material formulations or modeling and support material formulations or modifications thereof e.g., following curing). All these operations are well-known to those skilled in the art of solid freeform fabrication.

[0139] In some exemplary embodiments of the invention an object is manufactured by dispensing two or more different modeling material formulations, each material formulation from a different array of nozzles (belonging to the same or different printing heads) of the AM apparatus. In some embodiments, two or more such arrays of nozzles that dispense different modeling material formulations are both located in the same printing head of the AM apparatus. In some embodiments, arrays of nozzles that dispense different modeling material formulations are located in separate printing heads, for example, a first array of nozzles dispensing a first modeling material formulation is located in a first printing head, and a second array of nozzles dispensing a second modeling material formulation is located in a second printing head.

[0140] In some embodiments, an array of nozzles that dispense a modeling material formulation and an array of nozzles that dispense a support material formulation are both located in the same printing head. In some embodiments, an array of nozzles that dispense a modeling material formulation and an array of nozzles that dispense a support material formulation are both located in separate the same printing head. A representative and non-limiting example of a system 110 suitable for AM of an object 112 according to some embodiments of the present invention is illustrated in FIG. 1A. System 110 comprises an additive manufacturing apparatus 114 having a dispensing unit 16 which comprises a plurality of printing heads. Each head preferably comprises one or more arrays of nozzles 122, typically mounted on an orifice plate 121, as illustrated in FIGs. 2A-C described below, through which a liquid building material formulation 124 is dispensed.

[0141] Preferably, but not obligatorily, apparatus 114 is a three-dimensional printing apparatus, in which case the printing heads are printing heads, and the building material formulation is dispensed via inkjet technology. This need not necessarily be the case, since, for some applications, it may not be necessary for the additive manufacturing apparatus to employ three-dimensional printing techniques. Representative examples of additive manufacturing apparatus contemplated according to various exemplary embodiments of the present invention include, without limitation, fused deposition modeling apparatus and fused material formulation deposition apparatus.

[0142] Each printing head is optionally and preferably fed via one or more building material formulation reservoirs which may optionally include a temperature control unit (e.g. , a temperature sensor and / or a heating device), and a material formulation level sensor. To dispense the building material formulation, a voltage signal is applied to the printing heads to selectively deposit droplets of material formulation via the printing head nozzles, for example, as in piezoelectric inkjet printing technology. Another example includes thermal inkjet printing heads. In these types of heads, there are heater elements in thermal contact with the building material formulation, for heating the building material formulation to form gas bubbles therein, upon activation of the heater elements by a voltage signal. The gas bubbles generate pressures in the building material formulation, causing droplets of building material formulation to be ejected through the nozzles. Piezoelectric and thermal printing heads are known to those skilled in the art of solid freeform fabrication. For any types of inkjet printing heads, the dispensing rate of the head depends on the number of nozzles, the type of nozzles and the applied voltage signal rate (frequency).

[0143] Preferably, but not obligatorily, the overall number of dispensing nozzles or nozzle arrays is selected such that half of the dispensing nozzles are designated to dispense support material formulation and half of the dispensing nozzles are designated to dispense modeling material formulation, i.e. the number of nozzles jetting modeling material formulations is the same as the number of nozzles jetting support material formulation. In the representative example of FIG. 1 A, four printing heads 16a, 16b, 16c and 16d are illustrated. Each of heads 16a, 16b, 16c and 16d has a nozzle array. In this Example, heads 16a and 16b can be designated for modeling material formulation / s and heads 16c and 16d can be designated for support material formulation. Thus, head 16a can dispense one modeling material formulation, head 16b can dispense another modeling material formulation and heads 16c and 16d can both dispense support material formulation. In an alternative embodiment, heads 16c and 16d, for example, may be combined in a single head having two nozzle arrays for depositing support material formulation. In a further alternative embodiment any one or more of the printing heads may have more than one nozzle arrays for depositing more than one material formulation, e.g. two nozzle arrays for depositing two different modeling material formulations or a modeling material formulation and a support material formulation, each formulation via a different array or number of nozzles.

[0144] Yet it is to be understood that it is not intended to limit the scope of the present invention and that the number of modeling material formulation printing heads (modeling heads) and the number of support material formulation printing heads (support heads) may differ. Generally, the number of arrays of nozzles that dispense modeling material formulation, the number of arrays of nozzles that dispense support material formulation, and the number of nozzles in each respective array are selected such as to provide a predetermined ratio, a, between the maximal dispensing rate of the support material formulation and the maximal dispensing rate of modeling material formulation. The value of the predetermined ratio, a, is preferably selected to ensure that in each formed layer, the height of modeling material formulation equals the height of support material formulation. Typical values for a are from about 0.6 to about 1.5.

[0145] For example, for a = 1, the overall dispensing rate of support material formulation is generally the same as the overall dispensing rate of the modeling material formulation when all the arrays of nozzles operate.

[0146] Apparatus 114 can comprise, for example, M modeling heads each having m arrays of p nozzles, and S support heads each having s arrays of q nozzles such that Mxmxp = Sxsxq. Each of the Mxm modeling arrays and Sxs support arrays can be manufactured as a separate physical unit, which can be assembled and disassembled from the group of arrays. In this embodiment, each such array optionally and preferably comprises a temperature control unit and a material formulation level sensor of its own, and receives an individually controlled voltage for its operation.

[0147] Apparatus 114 can further comprise a solidifying device 324 which can include any device configured to emit light, heat or the like that may cause the deposited material formulation to harden. For example, solidifying device 324 can comprise one or more radiation sources, which can be, for example, an ultraviolet or visible or infrared lamp, or other sources of electromagnetic radiation, or electron beam source, depending on the modeling material formulation being used. In some embodiments of the present invention, solidifying device 324 serves for curing or solidifying the modeling material formulation.

[0148] In addition to solidifying device 324, apparatus 114 optionally and preferably comprises an additional radiation source 328 for solvent evaporation. Radiation source 328 optionally and preferably generates infrared radiation. In various exemplary embodiments of the invention solidifying device 324 comprises a radiation source generating ultraviolet radiation, and radiation source 328 generates infrared radiation.

[0149] In some embodiments of the present invention apparatus 114 comprises cooling system 134 such as one or more fans or the like

[0150] The printing head(s) and radiation source(s) are preferably mounted in a frame or block 128 which is preferably operative to reciprocally move over a tray 360, which serves as the working surface. In some embodiments of the present invention the radiation sources are mounted in the block such that they follow in the wake of the printing heads to at least partially cure or solidify the material formulations just dispensed by the printing heads. Tray 360 is positioned horizontally. According to the common conventions an X-Y-Z Cartesian coordinate system is selected such that the X-Y plane is parallel to tray 360. Tray 360 is preferably configured to move vertically (along the Z direction), typically downward. In various exemplary embodiments of the invention, apparatus 114 further comprises one or more leveling devices 132, e.g. a roller 326. Leveling device 326 serves to straighten, level and / or establish a thickness of the newly formed layer prior to the formation of the successive layer thereon. Leveling device 326 preferably comprises a waste collection device 136 for collecting the excess material formulation generated during leveling. Waste collection device 136 may comprise any mechanism that delivers the material formulation to a waste tank or waste cartridge.

[0151] In use, the printing heads of unit 16 move in a scanning direction, which is referred to herein as the X direction, and selectively dispense building material formulation in a predetermined configuration in the course of their passage over tray 360. The building material formulation typically comprises one or more types of support material formulation and one or more types of modeling material formulation. The passage of the printing heads of unit 16 is followed by the curing of the modeling material formulation(s) by radiation source 126. In the reverse passage of the heads, back to their starting point for the layer just deposited, an additional dispensing of building material formulation may be carried out, according to predetermined configuration. In the forward and / or reverse passages of the printing heads, the layer thus formed may be straightened by leveling device 326, which preferably follows the path of the printing heads in their forward and / or reverse movement. Once the printing heads return to their starting point along the X direction, they may move to another position along an indexing direction, referred to herein as the Y direction, and continue to build the same layer by reciprocal movement along the X direction. Alternately, the printing heads may move in the Y direction between forward and reverse movements or after more than one forward-reverse movement. The series of scans performed by the printing heads to complete a single layer is referred to herein as a single scan cycle.

[0152] Once the layer is completed, tray 360 is lowered in the Z direction to a predetermined Z level, according to the desired thickness of the layer subsequently to be printed. The procedure is repeated to form three-dimensional object 112 in a layerwise manner.

[0153] In another embodiment, tray 360 may be displaced in the Z direction between forward and reverse passages of the printing head of unit 16, within the layer. Such Z displacement is carried out in order to cause contact of the leveling device with the surface in one direction and prevent contact in the other direction.

[0154] System 110 optionally and preferably comprises a building material formulation supply system 330 which comprises the building material formulation containers or cartridges and supplies a plurality of building material formulations to fabrication apparatus 114.

[0155] A control unit 152 controls fabrication apparatus 114 and optionally and preferably also supply system 330. Control unit 152 typically includes an electronic circuit configured to perform the controlling operations. Control unit 152 preferably communicates with a data processor 154 which transmits digital data pertaining to fabrication instructions based on computer object data, e.g., a CAD configuration represented on a computer readable medium in a form of a Standard Tessellation Language (STL) format or the like. Typically, control unit 152 controls the voltage applied to each printing head or each nozzle array and the temperature of the building material formulation in the respective printing head or respective nozzle array.

[0156] Once the manufacturing data is loaded to control unit 152 it can operate without user intervention. In some embodiments, control unit 152 receives additional input from the operator, e.g., using data processor 154 or using a user interface 116 communicating with unit 152. User interface 116 can be of any type known in the art, such as, but not limited to, a keyboard, a touch screen and the like. For example, control unit 152 can receive, as additional input, one or more building material formulation types and / or attributes, such as, but not limited to, color, characteristic distortion and / or transition temperature, viscosity, electrical property, magnetic property. Other attributes and groups of attributes are also contemplated.

[0157] Another representative and non-limiting example of a system 10 suitable for AM of an object according to some embodiments of the present invention is illustrated in FIGs. 1B-D. FIGs. 1B-D illustrate a top view (FIG. IB), a side view (FIG. 1C) and an isometric view (FIG. ID) of system 10.

[0158] In the present embodiments, system 10 comprises a tray 12 and a plurality of inkjet printing heads 16, each having one or more arrays of nozzles with respective one or more pluralities of separated nozzles. The material used for the three-dimensional printing is supplied to heads 16 by a building material supply system 42. Tray 12 can have a shape of a disk or it can be annular. Nonround shapes are also contemplated, provided they can be rotated about a vertical axis.

[0159] Tray 12 and heads 16 are optionally and preferably mounted such as to allow a relative rotary motion between tray 12 and heads 16. This can be achieved by (i) configuring tray 12 to rotate about a vertical axis 14 relative to heads 16, (ii) configuring heads 16 to rotate about vertical axis 14 relative to tray 12, or (iii) configuring both tray 12 and heads 16 to rotate about vertical axis 14 but at different rotation velocities (e.g., rotation at opposite direction). While some embodiments of system 10 are described below with a particular emphasis to configuration (i) wherein the tray is a rotary tray that is configured to rotate about vertical axis 14 relative to heads 16, it is to be understood that the present application contemplates also configurations (ii) and (iii) for system 10. Any one of the embodiments of system 10 described herein can be adjusted to be applicable to any of configurations (ii) and (iii), and one of ordinary skills in the art, provided with the details described herein, would know how to make such adjustment.

[0160] In the following description, a direction parallel to tray 12 and pointing outwardly from axis 14 is referred to as the radial direction r, a direction parallel to tray 12 and perpendicular to the radial direction r is referred to herein as the azimuthal direction <p, and a direction perpendicular to tray 12 is referred to herein is the vertical direction z.

[0161] The term “radial position,” as used herein, refers to a position on or above tray 12 at a specific distance from axis 14. When the term is used in connection to a printing head, the term refers to a position of the head which is at specific distance from axis 14. When the term is used in connection to a point on tray 12, the term corresponds to any point that belongs to a locus of points that is a circle whose radius is the specific distance from axis 14 and whose center is at axis 14.

[0162] The term “azimuthal position,” as used herein, refers to a position on or above tray 12 at a specific azimuthal angle relative to a predetermined reference point. Thus, radial position refers to any point that belongs to a locus of points that is a straight line forming the specific azimuthal angle relative to the reference point.

[0163] The term “vertical position,” as used herein, refers to a position over a plane that intersect the vertical axis 14 at a specific point. Tray 12 serves as a building platform for three-dimensional printing. The working area on which one or objects are printed is typically, but not necessarily, smaller than the total area of tray 12. In some embodiments of the present invention the working area is annular. The working area is shown at 26. In some embodiments of the present invention tray 12 rotates continuously in the same direction throughout the formation of object, and in some embodiments of the present invention tray reverses the direction of rotation at least once (e.g., in an oscillatory manner) during the formation of the object. Tray 12 is optionally and preferably removable. Removing tray 12 can be for maintenance of system 10, or, if desired, for replacing the tray before printing a new object. In some embodiments of the present invention system 10 is provided with one or more different replacement trays (e.g., a kit of replacement trays), wherein two or more trays are designated for different types of objects (e.g., different weights) different operation modes (e.g., different rotation speeds), etc. The replacement of tray 12 can be manual or automatic, as desired. When automatic replacement is employed, system 10 comprises a tray replacement device 36 configured for removing tray 12 from its position below heads 16 and replacing it by a replacement tray (not shown). In the representative illustration of FIG. IB tray replacement device 36 is illustrated as a drive 38 with a movable arm 40 configured to pull tray 12, but other types of tray replacement devices are also contemplated.

[0164] Exemplified embodiments for the printing head 16 are illustrated in FIGs. 2A-2C. These embodiments can be employed for any of the AM systems described above, including, without limitation, system 110 and system 10.

[0165] FIGs. 2A-B illustrate a printing head 16 with one (FIG. 2A) and two (FIG. 2B) nozzle arrays 22. The nozzles in the array are preferably aligned linearly, along a straight line. In embodiments in which a particular printing head has two or more linear nozzle arrays, the nozzle arrays are optionally and preferably can be parallel to each other. When a printing head has two or more arrays of nozzles (e.g., FIG. 2B) all arrays of the head can be fed with the same building material formulation, or at least two arrays of the same head can be fed with different building material formulations.

[0166] When a system similar to system 110 is employed, all printing heads 16 are optionally and preferably oriented along the indexing direction with their positions along the scanning direction being offset to one another.

[0167] When a system similar to system 10 is employed, all printing heads 16 are optionally and preferably oriented radially (parallel to the radial direction) with their azimuthal positions being offset to one another. Thus, in these embodiments, the nozzle arrays of different printing heads are not parallel to each other but are rather at an angle to each other, which angle being approximately equal to the azimuthal offset between the respective heads. For example, one head can be oriented radially and positioned at azimuthal position 91, and another head can be oriented radially and positioned at azimuthal position 92. In this example, the azimuthal offset between the two heads is 91-92, and the angle between the linear nozzle arrays of the two heads is also 91-92.

[0168] In some embodiments, two or more printing heads can be assembled to a block of printing heads, in which case the printing heads of the block are typically parallel to each other. A block including several inkjet printing heads 16a, 16b, 16c is illustrated in FIG. 2C.

[0169] In some embodiments, system 10 comprises a stabilizing structure 30 positioned below heads 16 such that tray 12 is between stabilizing structure 30 and heads 16. Stabilizing structure 30 may serve for preventing or reducing vibrations of tray 12 that may occur while inkjet printing heads 16 operate. In configurations in which printing heads 16 rotate about axis 14, stabilizing structure 30 preferably also rotates such that stabilizing structure 30 is always directly below heads 16 (with tray 12 between heads 16 and tray 12).

[0170] Tray 12 and / or printing heads 16 is optionally and preferably configured to move along the vertical direction z, parallel to vertical axis 14 so as to vary the vertical distance between tray 12 and printing heads 16. In configurations in which the vertical distance is varied by moving tray 12 along the vertical direction, stabilizing structure 30 preferably also moves vertically together with tray 12. In configurations in which the vertical distance is varied by heads 16 along the vertical direction, while maintaining the vertical position of tray 12 fixed, stabilizing structure 30 is also maintained at a fixed vertical position.

[0171] The vertical motion can be established by a vertical drive 28. Once a layer is completed, the vertical distance between tray 12 and heads 16 can be increased (e.g., tray 12 is lowered relative to heads 16) by a predetermined vertical step, according to the desired thickness of the layer subsequently to be printed. The procedure is repeated to form a three-dimensional object in a layerwise manner.

[0172] The operation of inkjet printing heads 16 and optionally and preferably also of one or more other components of system 10, e.g., the motion of tray 12, are controlled by a controller 20. The controller can have an electronic circuit and a non-volatile memory medium readable by the circuit, wherein the memory medium stores program instructions which, when read by the circuit, cause the circuit to perform control operations as further detailed below.

[0173] Controller 20 can also communicate with a host computer 24 which transmits digital data pertaining to fabrication instructions based on computer object data, e.g., in a form of a Standard Tessellation Language (STL) or a StereoLithography Contour (SLC) format, Virtual Reality Modeling Language (VRML), Additive Manufacturing File (AMF) format, Drawing Exchange Format (DXF), Polygon File Format (PLY), 3D Manufacturing Format (3MF), Object file format (OBJ), or any other format suitable for Computer-Aided Design (CAD). The object data formats are typically structured according to a Cartesian system of coordinates. In these cases, computer 24 preferably executes a procedure for transforming the coordinates of each slice in the computer object data from a Cartesian system of coordinates into a polar system of coordinates. Computer 24 optionally and preferably transmits the fabrication instructions in terms of the transformed system of coordinates. Alternatively, computer 24 can transmit the fabrication instructions in terms of the original system of coordinates as provided by the computer object data, in which case the transformation of coordinates is executed by the circuit of controller 20.

[0174] The transformation of coordinates allows three-dimensional printing over a rotating tray. In non-rotary systems with a stationary tray with the printing heads typically reciprocally move above the stationary tray along straight lines. In such systems, the printing resolution is the same at any point over the tray, provided the dispensing rates of the heads are uniform. In system 10, unlike non-rotary systems, not all the nozzles of the head points cover the same distance over tray 12 during at the same time. The transformation of coordinates is optionally and preferably executed so as to ensure equal amounts of excess material formulation at different radial positions. Representative examples of coordinate transformations according to some embodiments of the present invention are provided in FIGs. 3A-B, showing three slices of an object (each slice corresponds to fabrication instructions of a different layer of the objects), where FIG. 3A illustrates a slice in a Cartesian system of coordinates and FIG. 3B illustrates the same slice following an application of a transformation of coordinates procedure to the respective slice.

[0175] Typically, controller 20 controls the voltage applied to the respective component of the system 10 based on the fabrication instructions and based on the stored program instructions as described below.

[0176] Generally, controller 20 controls printing heads 16 to dispense, during the rotation of tray 12, droplets of building material formulation in layers, such as to print a three-dimensional object on tray 12.

[0177] System 10 optionally and preferably comprises one or more radiation sources 18, which can be, for example, an ultraviolet or visible or infrared lamp, or other sources of electromagnetic radiation, or electron beam source, depending on the modeling material formulation being used. Radiation source can include any type of radiation emitting device, including, without limitation, light emitting diode (LED), digital light processing (DLP) system, resistive lamp and the like. Radiation source 18 serves for curing or solidifying the modeling material formulation. In various exemplary embodiments of the invention the operation of radiation source 18 is controlled by controller 20 which may activate and deactivate radiation source 18 and may optionally also control the amount of radiation generated by radiation source 18.

[0178] In some embodiments of the invention, system 10 further comprises one or more leveling devices 32 which can be manufactured as a roller or a blade. Leveling device 32 serves to straighten the newly formed layer prior to the formation of the successive layer thereon. In some embodiments, leveling device 32 has the shape of a conical roller positioned such that its symmetry axis 34 is tilted relative to the surface of tray 12 and its surface is parallel to the surface of the tray. This embodiment is illustrated in the side view of system 10 (FIG. 1C).

[0179] The conical roller can have the shape of a cone or a conical frustum.

[0180] The opening angle of the conical roller is preferably selected such that there is a constant ratio between the radius of the cone at any location along its axis 34 and the distance between that location and axis 14. This embodiment allows roller 32 to efficiently level the layers, since while the roller rotates, any point p on the surface of the roller has a linear velocity which is proportional (e.g., the same) to the linear velocity of the tray at a point vertically beneath point p. In some embodiments, the roller has a shape of a conical frustum having a height h, a radius Ri at its closest distance from axis 14, and a radius R2 at its farthest distance from axis 14, wherein the parameters h, R\ and R satisfy the relation R\IRz=(R-h)lh and wherein R is the farthest distance of the roller from axis 14 (for example, R can be the radius of tray 12).

[0181] The operation of leveling device 32 is optionally and preferably controlled by controller 20 which may activate and deactivate leveling device 32 and may optionally also control its position along a vertical direction (parallel to axis 14) and / or a radial direction (parallel to tray 12 and pointing toward or away from axis 14.

[0182] In some embodiments of the present invention printing heads 16 are configured to reciprocally move relative to tray along the radial direction r. These embodiments are useful when the lengths of the nozzle arrays 22 of heads 16 are shorter than the width along the radial direction of the working area 26 on tray 12. The motion of heads 16 along the radial direction is optionally and preferably controlled by controller 20.

[0183] Herein throughout, the phrases “building material formulation”, “uncured building material”, “uncured building material formulation”, “building material” and other variations therefore collectively describe the materials that are dispensed to sequentially form the layers, as described herein. This phrase encompasses uncured materials dispensed so as to form the object, namely, one or more uncured modeling material formulation(s), and uncured materials dispensed so as to form the support, namely uncured support material formulations. Herein throughout, the term “object” describes a final product of the additive manufacturing. This term refers to the product obtained by a method as described herein, after removal of the support material, if such has been used as part of the uncured building material, and optionally after further treatment (e.g., exposure to second curing condition as described herein). The object therefore typically consists (at least 95 weight percent) of a cured (hardened, solidified) modeling material or a combination of two or more modeling materials. In some applications, the object includes, in at least a portion thereof, partially cured modeling material(s).

[0184] The term "object" as used herein throughout refers to a whole object or a part thereof. Herein throughout, the phrase “cured modeling material” which is also referred to herein as “hardened” or solidified” modeling material describes the part of the building material that forms the object, as defined herein, upon exposing the dispensed building material to a curing condition (and optionally further treatment), and, optionally, if a support material has been dispensed, removal of the cured support material, as described herein. The hardened modeling material can be a single hardened material or a mixture of two or more hardened materials, depending on the modeling material formulations used in the method, as described herein.

[0185] The phrases “cured modeling material”, “hardened modeling material”, “solidified modeling material” or “cured / hardened / solidified modeling material formulation” can be regarded as a cured building material wherein the building material consists only of a modeling material formulation (and not of a support material formulation). That is, this phrase refers to the portion of the building material, which is used to provide the final object.

[0186] Herein throughout, the phrase “modeling material formulation”, which is also referred to herein interchangeably as “modeling formulation”, “modeling material” “model material” or simply as “formulation”, describes a part or all of the uncured building material which is dispensed so as to form the object, as described herein. The modeling material formulation is an uncured modeling formulation (unless specifically indicated otherwise), which, upon exposure to a condition that effects curing, may form the object or a part thereof.

[0187] In some embodiments of the present invention, a modeling material formulation is formulated for use in three-dimensional inkjet printing and is able to form a three-dimensional object on its own,

[0188]

[0189] without having to be mixed or combined with any other substance.

[0190] An uncured building material can comprise one or more modeling material formulations, and can be dispensed such that different parts of the object are made, upon being hardened, of different cured modeling formulations, and hence are made of different hardened (e.g., cured) modeling materials or different mixtures of hardened (e.g., cured) modeling materials. The final three-dimensional object is made of the modeling material or a combination of modeling materials or a combination of modeling material / s and support material / s or modification thereof (e.g., following curing). All these operations are well-known to those skilled in the art of solid freeform fabrication.

[0191] In some exemplary embodiments of the invention, an object is manufactured by dispensing a building material that comprises two or more different modeling material formulations, each modeling material formulation from a different dispensing head and / or nozzle of the inkjet printing apparatus. The modeling material formulations are optionally and preferably concurrently deposited during the same pass of the printing heads. The modeling material formulations and / or combination of formulations within a layer are selected according to the desired properties of the object and according to the method parameters described herein.

[0192] According to some of any of the embodiments described herein, each of the modeling material formulations comprises one or more curable materials.

[0193] Herein throughout, a “curable material” or a “solidifiable material” is a compound (e.g., monomeric or oligomeric or polymeric compound) which, when exposed to a curing condition (e.g., curing energy), as described herein, solidifies or hardens to form a cured modeling material as defined herein. Curable materials are typically polymerizable materials, which undergo polymerization and / or cross-linking when exposed to a suitable energy source. A curable or solidifiable material is typically such that its viscosity increases by at least one order of magnitude when it is exposed to a curing condition.

[0194] In some of any of the embodiments described herein, a curable material can be a monomer, an oligomer or a short-chain polymer, each being polymerizable as described herein.

[0195] In some of any of the embodiments described herein, when a curable material is exposed to curing energy (e.g., radiation), it polymerizes by any one, or combination, of chain elongation and cross -linking.

[0196] In some of any of the embodiments described herein, a curable material is a monomer or a mixture of monomers which can form a polymeric modeling material upon a polymerization reaction, when exposed to a curing condition at which the polymerization reaction occurs. Such curable materials are also referred to herein as monomeric curable materials.

[0197] In some of any of the embodiments described herein, a curable material is an oligomer or a mixture of oligomers which can form a polymeric modeling material upon a polymerization reaction, when exposed to a curing condition at which the polymerization reaction occurs. Such curable materials are also referred to herein as oligomeric curable materials. In some of any of the embodiments described herein, a curable material, whether monomeric or oligomeric, can be a mono-functional curable material or a multi-functional curable material.

[0198] Herein, a mono-functional curable material comprises one functional group that can undergo polymerization when exposed to a curing condition (e.g., curing energy).

[0199] A multi-functional curable material comprises two or more, e.g., 2, 3, 4 or more, functional groups that can undergo polymerization when exposed to a curing condition. Multi-functional curable materials can be, for example, di-functional, tri-functional or tetra-functional curable materials, which comprise 2, 3 or 4 groups that can undergo polymerization, respectively. The two or more functional groups in a multi-functional curable material are typically linked to one another by a linking moiety, as defined herein. When the linking moiety is an oligomeric moiety, the multifunctional group is an oligomeric multi-functional curable material.

[0200] Exemplary curable materials that are commonly used in additive manufacturing and in some of the present embodiments are acrylic materials.

[0201] Herein throughout, the term acrylic materials collectively encompass materials bearing one or more acrylate, methacrylate, acrylamide and / or methacrylamide group(s).

[0202] The curable materials included in the first and second formulations described herein may be defined by the properties provided by each material, when hardened. That is, the materials may be defined by properties of a material formed upon exposure to a curing condition, for example, upon polymerization. These properties (e.g., Tg, HDT), are of a polymeric material formed upon curing any of the described curable materials alone.

[0203] As used herein, each of the terms “curing” and “hardening” describes a process in which a formulation is hardened. These terms encompass polymerization of monomer(s) and / or oligomer(s) and / or cross-linking of polymeric chains (either of a polymer present before curing or of a polymeric material formed in a polymerization of the monomers or oligomers). The product of a curing reaction or of a hardening is therefore typically a polymeric material and in some cases a cross-linked polymeric material.

[0204] Partial curing or hardening as used herein encompasses a curing or hardening process that does not reach completion, that is, for example, a process that is effected up to a hardening degree, as defined hereinafter, which is less than 100 %, less than 90 %, or less than 80 %. Material that is partially cured may stay in a liquid-jelly state. Complete curing or hardening as used herein is curing or hardening to a degree of at least 80 %, or at least 90 %, or of about 100%, for example, a curing or hardening process that results in a solidified material. A “degree of hardening” as used herein represents the extent at which curing is effected, that is, the extent at which curable materials underwent polymerization and / or cross-linking. When a curable material is a polymerizable material, this phrase encompasses both a mol % of the curable materials in a formulation that underwent polymerization and / or cross-linking, upon exposure to a curing condition; and / or the degree at which polymerization and / or cross-linking was effected, for example, the degree of chain elongation and / or cross-linking. Determining a degree of polymerization can be performed by methods known to those skilled in the art.

[0205] A “green body object” as used herein is an object formed by an AM process that has at least a portion that has only been partially hardened or solidified and requires additional hardening to obtain a fully solidified object.

[0206] Herein, the phrase “a condition that affects curing” or “a condition for inducing curing”, which is also referred to herein interchangeably as “curing condition” or “curing inducing condition” describes a condition which, when applied to a formulation that contains a curable material, induces polymerization of monomer(s) and / or oligomer(s) and / or cross-linking of polymeric chains. Such a condition can include, for example, application of a curing energy, as described hereinafter, to the curable material(s), and / or contacting the curable material(s) with chemically reactive components such as catalysts, co-catalysts, and activators.

[0207] When a condition that induces curing comprises application of a curing energy, the phrase “exposing to a curing condition” means that the dispensed layers are exposed to the curing energy and the exposure is typically performed by applying a curing energy to the dispensed layers.

[0208] A “curing energy” typically includes application of radiation or application of heat.

[0209] The radiation can be electromagnetic radiation (e.g., ultraviolet or visible light), or electron beam radiation, or ultrasound radiation or microwave radiation, depending on the materials to be cured. The application of radiation (or irradiation) is effected by a suitable radiation source. For example, an ultraviolet or visible or infrared or Xenon or Mercury lamp can be employed, as described herein.

[0210] A curable material or system that undergoes curing upon exposure to radiation is referred to herein interchangeably as “photopolymerizable” or “photoactivatable” or “photocurable”.

[0211] In some of any of the embodiments described herein, a curable material is a photopolymerizable material, which polymerizes or undergoes cross-linking upon exposure to radiation, as described herein, and in some embodiments the curable material is a UV-curable material, which polymerizes or undergoes cross-linking upon exposure to UV-vis radiation, as described herein. In some embodiments, a curable material as described herein includes a polymerizable material that polymerizes via photo-induced radical polymerization.

[0212] When the curing energy comprises heat, the curing is also referred to herein and in the art as “thermal curing” and comprises application of thermal energy. Applying thermal energy can be effected, for example, by heating a receiving medium onto which the layers are dispensed or a chamber hosting the receiving medium, as described herein. In some embodiments, the heating is effected using a resistive heater.

[0213] In some embodiments, the heating is affected by irradiating the dispensed layers by heatinducing radiation. Such irradiation can be effected, for example, by means of an IR lamp or Xenon lamp, operated to emit radiation onto the deposited layer.

[0214] A curable material or system that undergoes curing upon exposure to heat is referred to herein as “thermally-curable” or “thermally-activatable” or “thermally-polymerizable”.

[0215] Some curable materials can harden via thermal and / or photo-induced curing.

[0216] A formulation that comprises one or more curable materials (e.g., a support material formulation or a modeling material formulation) is also referred to herein as a curable formulation.

[0217] A method of additive manufacturing of a three-dimensional object, according to some embodiments of the present invention, typically comprises obtaining 3D printing data in any of the aforementioned computer object data formats, and proceeds by dispensing droplets of one or more uncured building material formulation(s) to form a layer. The building material formulation comprises one or more modeling material formulations, at least one of the modeling material formulations is a curable formulation as described herein in any of the respective embodiments, and optionally a support material formulation as described herein in any of the respective embodiments and any combination thereof.

[0218] The modeling material formulation is preferably dispensed in a configured pattern corresponding to the shape of the object and in accordance with the computer object data. The other building material formulations are preferably dispensed in accordance with the computer object data, but not necessarily in accordance with the shape of the object, since these building material formulations are typically sacrificial (serving as a support material as described herein).

[0219] Optionally, before being dispensed, the uncured building material, or a part thereof (e.g., one or more formulations of the building material), is heated, prior to being dispensed. These embodiments are particularly useful for uncured building material formulations having relatively high viscosity at the operation temperature of the working chamber of a 3D inkjet printing system. The heating of the formulation(s) is preferably to a temperature that allows jetting the respective formulation through a nozzle of a printing head of a 3D inkjet printing system. In some embodiments of the present invention, the heating is to a temperature at which the respective formulation exhibits a viscosity of no more than X centipoises, where X is about 30 centipoises, preferably about 25 centipoises and more preferably about 20 centipoises, or 18 centipoises, or 16 centipoises, or 14 centipoises, or 12 centipoises, or 10 centipoises, or even lower. It is to be noted that higher viscosities can also be applicable, particularly, but not obligatorily, in cases where the inkjet printing head is adapted for dispensing high viscosity formulations. Thus, also contemplated is heating the formulation(s) to a temperature at which the respective formulation exhibits a viscosity of up to 100, 150, 200 and even 300 centipoises.

[0220] The heating can be executed before loading the respective formulation into the printing head of the AM (e.g., 3D inkjet printing) system, or while the formulation is in the printing head or while the composition passes through the nozzle of the printing head.

[0221] In some embodiments, the heating is executed before loading of the respective formulation into the dispensing (e.g., inkjet printing) head, so as to avoid clogging of the dispensing (e.g., inkjet printing) head by the formulation in case its viscosity is too high.

[0222] In some embodiments, the heating is executed by heating the dispensing (e.g., inkjet printing) heads, at least while passing the modeling material formulation(s) through the nozzle of the dispensing (e.g., inkjet printing) head.

[0223] In some embodiments, a newly dispensed layer is optionally straightened, for example, using a leveling device 32 or 132, which is optionally and preferably rotatable.

[0224] A method or process of additive manufacturing according to some embodiments of the present invention optionally and preferably proceeds to exposing the deposited layer to a curing condition as described herein (e.g., curing energy is applied; for example, irradiation), e.g., by means of a hardening device, for example, a radiation source as described herein. Preferably, the curing is applied to each individual layer following the deposition of the layer and prior to the deposition of the previous layer. Optionally, the deposited (dispensed) layers are exposed to the curing condition other than a curing energy, such as, but not limited to, contact with a chemical reagent or exposure to the environment.

[0225] Depositing or dispensing a layer and exposing to a curing condition are preferably executed sequentially a plurality of times so that a plurality of layers are sequentially dispensed and solidified. The layers are dispensed to form a stack of model layers made of a modeling material formulation, and optionally a sacrificial structure made of a support material formulation such as described herein, wherein the stack of model layers and the sacrificial structure are separable from each other in a manner that maintains the shape and size of the stack of model layers without deformation. In various exemplary embodiments of the invention the dispensing and exposing are executed to form, for at least a portion of layers, voxel elements containing different building (e.g., modeling) material formulations at interlaced locations.

[0226] In some embodiments, at least one, or at least a few (e.g., at least 10, at least 20, at least 30 at least 40, at least 50, at least 60, at least 80, or more), of the layers is / are formed by dispensing droplets of two or more building (e.g., modeling) material formulations at interlaced locations, each formulation from a different nozzle array. These building material formulations can include: (i) two or more of a modeling material formulation as described herein in any of the respective embodiments, which differ from one another, for example, by opacity, color, toughness, (ii) one or more of a modeling material formulation as described herein in any of the respective embodiments and one or more of a modeling material formulation that features a different toughness, (iii) at least one modeling material formulation and at least one support material formulation as described herein in any of the respective embodiments, and / or (iv) two or more support material formulations as described herein in any of the respective embodiments.

[0227] Some embodiments contemplate the fabrication of an object by dispensing different material formulations from different arrays of nozzles (belonging to the same or different printing head). These embodiments provide, inter alia, the ability to select material formulations from a given number of material formulations and define desired combinations of the selected material formulations and their properties. According to the present embodiments, the spatial locations of the deposition of each material formulation with the layer is defined, either to effect occupation of different three-dimensional spatial locations by different material formulations, or to effect occupation of substantially the same three-dimensional location or adjacent three-dimensional locations by two or more different material formulations so as to allow post deposition spatial combination of the material formulations within the layer, thereby to form a composite material formulation at the respective location or locations.

[0228] Any post deposition combination or mix of modeling material formulations is contemplated. For example, once a certain material formulation is dispensed it may preserve its original properties. However, when it is dispensed simultaneously with another modeling material formulation or other dispensed material formulations which are dispensed at the same or nearby locations, a composite material formulation having a different property or properties to the dispensed material formulations may be formed.

[0229] In some embodiments of the present invention the system dispenses digital material formulations for at least one of the layers. The phrase “digital material formulations”, as used herein and in the art, describes a combination of two or more material formulations on a pixel level or voxel level such that pixels or voxels of different material formulations are interlaced with one another over a region. Such digital material formulations may exhibit new properties that are affected by the selection of types of material formulations and / or the ratio and relative spatial distribution of two or more material formulations.

[0230] As used herein, a "voxel" of a layer refers to a physical three-dimensional elementary volume within the layer that corresponds to a single pixel of a bitmap describing the layer. The size of a voxel is approximately the size of a region that is formed by a building material, once the building material is dispensed at a location corresponding to the respective pixel, leveled, and solidified.

[0231] The present embodiments thus enable the deposition of a broad range of material formulation combinations, and the fabrication of an object which may consist of multiple different combinations of material formulations, in different parts of the object, according to the properties desired to characterize each part of the object.

[0232] Further details on the principles and operations of an AM system suitable for the present embodiments are found in U.S. Patent No. 9,031,680, and International Publication No. WO 2016 / 009426, the contents of which are hereby incorporated by reference.

[0233] According to some embodiments, the method comprises two or more modeling material formulations so as to form a shelled structure. The shelled structure typically comprises a layered core which is at least partially coated by one or more layered shells such that at least one layer of the core engages the same plane with a layer of at least one of the shells. The thickness of each shell, as measured perpendicularly to the surface of the structure, is typically at least 10 pm. In various exemplary embodiments of the invention, the core and the shell are different from each other in their thermo-mechanical properties. This is readily achieved by fabricating the core and shell from different modeling material formulations or different combinations of modeling material formulations. The thermo -mechanic al properties of the core and shell are referred to herein as "core thermo-mechanical properties" and "shell thermo-mechanical properties," respectively.

[0234] A representative and non-limiting example of a structure according to some embodiments of the present invention is shown in FIGs. 6A-D.

[0235] FIG. 6A is a schematic illustration of a perspective view of a structure 60, and FIG. 6B is a cross-sectional view of structure 60 along line A— A of FIG. 6A. For clarity of presentation a Cartesian coordinate system is also illustrated. Structure 60 comprises a plurality of layers 62 stacked along the z direction. Structure 60 is typically fabricated by an AM technique, e.g., using system 10, whereby the layers are formed in a sequential manner. Thus, the z direction is also referred to herein as the "build direction" of the structure. Layers 62 are, therefore, perpendicular to the build direction. Although structure 60 is shown as a cylinder, this need not necessarily be the case, since the structure of the present embodiments can have any shape.

[0236] The shell and core of structure 60 are shown at 64 and 66, respectively. As shown, the layers of core 66 and the layers of shell 64 are co-planar. The AM technique allows the simultaneous fabrication of shell 64 and core 66, whereby for a particular formed layer, the inner part of the layer constitutes a layer of the core, and the periphery of the layer, or part thereof, constitutes a layer of the shell.

[0237] A peripheral section of a layer which contributes to shell 64 is referred to herein as an "envelope region" of the layer. In the non-limiting example of FIGs. 6A and 6B, each of layers 62 has an envelope region. Namely, each layer in FIGs. 6A and 6B contributes both to the core and to the shell. However, this need not necessarily be the case, since, for some applications, it may be desired to have the core exposed to the environment in some regions. In these applications, at least some of the layers do not include an envelope region. A representative example of such configuration is illustrated in the cross-sectional view of FIG. 6C, showing some layers 68 which contribute to the core but not to the shell, and some layers 70 which contribute to both the core and the shell. In some embodiments, one or more layers do not include a region with core thermomechanical properties and comprise only a region with shell thermo-mechanical properties. These embodiments are particularly useful when the structure has one or more thin parts, wherein the layers forming those parts of the structure are preferably devoid of a core region. Also contemplated are embodiments in which one or more layers do not include a region with shell thermo-mechanical properties and comprise only a region with core thermo-mechanical properties.

[0238] The shell can, optionally and preferably, also cover structure 60 from above and / or below, relative to the z direction. In these embodiments, some layers at the top most and / or bottom most parts of structure 60 have at least one material property which is different from core 66. In various exemplary embodiments of the invention the top most and / or bottom most parts of structure 60 have the same material property as shell 64. A representative example of this embodiment is illustrated in FIG. 6D. The top / bottom shell of structure 60 may be thinner (e.g., 2 times thinner) than the side shell, e.g. when the top or bottom shell comprises a layer above or below the structure, and therefore has the same thickness as required for layers forming the object. A representative example of a layer 62 suitable for some embodiments of the present invention is illustrated in FIG. 6E. In the schematic illustration of FIG. 6E, which is not to be considered as limiting, layer 62 has a core region 902, an inner envelope region 904, at least partially, more preferably completely, surrounding core region 902, and an outer envelope region 906, at least partially, more preferably completely, surrounding inner envelope region 904.

[0239] Preferably, but not necessarily, outer envelope region 906 is the outermost region of layer 62.

[0240] Core region 902 preferably comprises a combination of at least two modeling formulations. The combination is optionally and preferably embodied in a voxelated manner wherein some voxels that form region 902 are made of one of the modeling martial formulations, other voxels are made of another one of the modeling martial formulations, and so on. In various exemplary embodiments of the invention core region 902 is made of a voxelated combination between the first modeling formulation and the second modeling formulation described below. The voxelated combination can be according to any distribution by which voxels occupied by the first formulation are interlaced within voxels occupied by the second formulation, such as, but not limited to, a random distribution.

[0241] The ratio between the number of voxels within region 902 that are occupied by the first modeling formulation and the number of voxels within region 902 that are occupied by the second modeling formulation is preferably from about 0.25 to about 0.45, or from about 0.25 to about 0.4, or from about 0.3 to about 0.4, e.g., about 0.33. In any embodiment of the invention, including any embodiment that includes these ratios, region 902 is optionally and preferably devoid of any material other than the first formulation and the second formulation described herein.

[0242] Further embodiments related to the ratio between the first modeling material formulation and the second modeling material formulation are provided hereinunder.

[0243] Inner envelope region 904 is preferably made of a single modeling formulation, for example, the first modeling formulation described below. Outer envelope region 906 is preferably made of a single modeling formulation, for example, the second modeling formulation described below.

[0244] The thickness of region 904, as measured within the plane of layer 62 and perpendicularly to the surface of structure 60, is preferably from about 0.1 mm to about 4 mm, or from about 0.1 mm to about 3.5 mm, or from about 0.1 mm to about 3 mm, or from about 0.1 mm to about 2.5 mm, or from about 0.1 mm to about 2 mm, or from about 0.2 mm to about 1.5 mm, or from about 0.3 mm to about 1.5 mm, or from about 0.4 mm to about 1.5 mm, or from about 0.4 mm to about 1.4 mm or from about 0.4 mm to about 1.3 mm or from about 0.4 mm to about 1.2 mm or from about 0.4 mm to about 1.1 mm. The thickness of region 906, as measured within the plane of layer 62 and perpendicularly to the surface of structure 60, is preferably from about from about 150 microns to about 600 microns, or from about from about 150 microns to about 550 microns, or from about from about 150 microns to about 500 microns, or from about from about 150 microns to about 450 microns, or from about from about 150 microns to about 400 microns, or from about from about 150 microns to about 350 microns or from about 180 microns to about 320 microns or from about 200 microns to about 300 microns or from about 220 microns to about 280 microns or from about 240 microns to about 260 microns.

[0245] In some embodiments of the present invention, layer 62 comprises an additional envelope region 908 between inner envelope region 904 and outer envelope region 906. Region 904 is preferably made of a combination, e.g., voxelated combination, of two or more modeling formulations. Typically, but not exclusively, region 904 is made of a voxelated combination including the modeling formulation making region 904 (the first modeling formulation in the above example) and the modeling formulation making region 906 (the second modeling formulation in the above example). It was found by the Inventors of the present invention that such configuration allows region 908 to serve as a stitching region that bonds region 906 to region 904.

[0246] The ratio between the number of voxels within region 908 that are occupied by the first modeling formulation and the number of voxels within region 902 that are occupied by the second modeling formulation is preferably from about 0.9 to about 1.1, e.g., about 1. In any embodiment of the invention, including any embodiment that includes these ratios, region 908 is optionally and preferably devoid of any material other than the first formulation and the second formulation described herein. The thickness of region 908, as measured within the plane of layer 62 and perpendicularly to the surface of structure 60, is preferably less than the thickness of region 904 and also less than the thickness of region 906. For example, the thickness of region 908 can be from about 70 microns to about 100 microns or from about 75 microns to about 95 microns or from about 80 microns to about 90 microns.

[0247] In some embodiments, one or more layers do not include a core region and comprise only envelope regions. These embodiments are particularly useful when the structure has one or more thin parts, wherein the layers forming those parts of the structure are preferably devoid of a core region.

[0248] FIG. 6F is a schematic illustration of a side view of structure 60 in embodiments of the invention in which at least some of the layers 62 of structure 60 comprise core region 902, envelope regions 904 and 906 and optionally also an additional envelope region 908 between regions 904 and 906. In these embodiments structure 60 optionally and preferably comprises a base section 910 and / or a top section 920, each optionally and preferably comprises a plurality of layers. The layers of sections 910 and 920 can be arranged such that one or more of the topmost layers 922 of top section 920 and one or more of the bottommost layers 912 of base section 910 are made of the same formulation at envelope region 906 described above. Alternatively, or more preferably additionally, the layers of sections 910 and 920 can be arranged such that one or more of the bottommost layers 924 of top section 920 and one or more of the topmost layers 914 of base section 910 are made of the same formulation at envelope region 904 described above. In some embodiments of the present invention at least one of base section 910 and top section 920 comprises one or more intermediate layers (respectively shown at 918, 928) that is made of the same or similar combination of formulations as region 908 described above.

[0249] For clarity of presentation, FIG. 6F shows a single layer for each of layers 912, 914, 918, 922, 924 and 928, however, this need not necessarily be the case, since, for some applications, at least one of these layers is embodied as a stack of layers. The number of layers in each stack is preferably selected such that the thickness, along the build direction (the z direction, in the present illustration) of the stack is approximately the same as the thickness of the respective envelope region. Specifically, the number of layers in stacks 912 and 922 is preferably selected such that the overall thickness of these stacks along the build direction is approximately the same (e.g., within 10%) as the thickness of outer envelope region 906 as measured in the plane of layer 62 and perpendicularly to the surface of structure 60, the number of layers in stacks 914 and 924 is preferably selected such that the overall thickness of these stacks along the build direction is approximately the same (e.g., within 10%) as the thickness of inner envelope region 904 as measured in the plane of layer 62 and perpendicularly to the surface of structure 60, and the number of layers in stacks 918 and 928 is preferably selected such that the overall thickness of these stacks along the build direction is approximately the same (e.g., within 10%) as the thickness of additional envelope region 908 as measured in the plane of layer 62 and perpendicularly to the surface of structure 60.

[0250] The present embodiments thus provide a method of layerwise fabrication of a three-dimensional object, in which for each of at least a few (e.g., at least two or at least three or at least 10 or at least 20 or at least 40 or at least 80) of the layers or all the layers, two or more modeling formulations are dispensed, optionally and preferably using system 10 or system 110, to form a core region and at least one envelope region at least partially surrounding core region. Each modeling formulation is preferably dispensed by jetting it out of a plurality of nozzles of a print head (e.g., print head 16). The dispensing is optionally and preferably in a voxelated manner.

[0251] The core region can be formed from two or more modeling material formulations, a first modeling formulation, which is a formulation as described herein in any of the respective embodiments, and a second modeling formulation, which is different from the first modeling material formulation. This is optionally and preferably, but not necessarily, achieved by interlacing voxels of the first modeling formulation and voxels of the second modeling formulation within the core according to a predetermined voxel ratio.

[0252] In some embodiments of the present invention the amount of the first modeling formulation is the core region is higher than 25 % or higher than 26 % or higher than 27 % or higher than 28 % or higher than 29 % or higher than 30 % of a total weight of core region. In some embodiments of the present invention the ratio between the weight of the first modeling formulation in the core region and the weight of the second modeling formulation in the core region is from about 0.1 to about 10, or from about 0.2 to about 5, or from about 0.2 to about 2, or from about 0.2 to about 1, or from about 0.2 to about 0.5, or from about 1 to about 10, or from about 2 to about 10, or from about 5 to about 10.

[0253] Preferably, the two modeling formulations forming the core region are selected such that the core region, when hardened, is characterized by HDT of at least 60 °C.

[0254] One or more of the envelope regions, if present, are optionally and preferably formed from one of the formulations, and preferably not from the other formulation. For example, an envelope region can be formed from the first modeling formulation but not the second modeling formulation, or be formed from the second modeling formulation but not the first modeling formulation.

[0255] Alternatively, the formulations of the present embodiments are used to form one of the envelope regions and not used to form the core region.

[0256] Once formed, the layer including the two modeling formulations is preferably exposed to curing energy so as to harden the formulations. This is optionally and preferably executed using hardening device 324 or radiation source 18.

[0257] In some of any of the embodiments described herein, the uncured building material further comprises a support material.

[0258] In some embodiments of any of the embodiments described herein, dispensing a building material formulation (uncured building material) further comprises dispensing support material formulation(s) which form the support material upon application of curing energy.

[0259] Dispensing the support material formulation, in some embodiments, is effected by inkjet printing head(s) other than the inkjet printing heads used for dispensing the first and second (and other) compositions forming the modeling material.

[0260] In some embodiments, exposing the building material to curing energy includes applying a curing energy (e.g., by irradiation) that affects curing of a support material formulation, to thereby obtain a cured support material. In some embodiments of any of the embodiments described herein, once a building material is cured, the method further comprises removing the cured support material. Any of the methods usable for removing a support material can be used, depending on the materials forming the modeling material and the support material. Such methods include, for example, mechanical removal of the cured support material and / or chemical removal of the cured support material by contacting the cured support material with a solution in which it is dissolvable (e.g., an alkaline aqueous solution).

[0261] In some embodiments, the method continues to removing the hardened support material, if present, from the printed object, to thereby reveal the final object.

[0262] In some embodiments of the present invention the removal of the hardened support material is by contacting the printed object with water, or an aqueous solution. The contacting can be made by immersing the printed object in static water or aqueous solution, or by immersing the printed object in circulating water, for example, a Jacuzzi, or by immersing the printed object in ultrasonic water bath, or by subjecting the printed object to mechanical dishwashing in water or aqueous solution. The removal can alternatively comprise subjecting the printed object to a jet of water or an aqueous solution.

[0263] According to some embodiments of any of the embodiments described herein, the printed object is subjected to a further treatment. In some embodiments, the further treatment is effected after removal of the hardened support material. Alternatively, it is effected prior to removal of the support material.

[0264] In some embodiments, the further treatment comprises photobleaching, for example, exposing the object to irradiation (e.g., UV irradiation), and optionally to thermal treatment. In exemplary embodiments, the further treatment comprises exposing the object to heat, preferably to a temperature that lower from the HDT of the object (e.g., 40-60, or 40-50 °C) and to UV irradiation (e.g., 400-500 nm), for a time period in a range of from 2 to 24, or from 8 to 24, or from 10 to 24, or from 12 to 24, or from 2 to 12, or from 4 to 12, of from 8 to 12, hours, including any intermediate values and subranges therebetween, although any other time periods are contemplated.

[0265] According to an aspect of some embodiments of the present invention, a method as described herein is effected while using a newly designed modeling material formulation that provides, when hardened (e.g., when exposed to a curing condition as described herein, preferably to irradiation as described herein, for example, UV-irradiation) a hardened material that exhibits improved toughness, as described herein. According to some embodiments, the modeling material formulation is a curable formulation, or photocurable (e.g., photopolymerizable) formulation, for example, UV-curable (e.g., UV-photopolymerizable) formulation, which provides the hardened material when it is exposed to irradiation (e.g., UV-irradiation).

[0266] According to the present embodiments, the newly designed formulation provides, upon exposure to a curing condition as described herein, a hardened material that exhibits impact resistance (Izod XY notched impact resistance, as described herein in any of the respective embodiments) of at least 40, or at least 50, J / m, for example, in a range of from 40 to 100, or from 50 to 100, or from 40 to 80, or from 50 to 80, or from 40 to 70, or from 50 to 70, or from 40 to 60, or from 60 to 100, or from 60 to 90, or from 60 to 80, J / mol.

[0267] According to some embodiments of the any of the embodiments described herein, the Izod XY notched impact resistance values represent the values obtained on Zwick / Roell HIT 5.5P machine as described in the Examples section that follows.

[0268] The newly designed formulation is also referred to herein as “tough” formulation and will now be described in further detail.

[0269] According to some embodiments of any of the embodiments described herein, there is provided a modeling material formulation usable for additive manufacturing of a three-dimensional object featuring in at least a portion thereof a hardened material that exhibits impact resistance (Izod XY notched impact resistance) of at least 40 or at least 50 J / m, as described herein.

[0270] According to some embodiments of any of the embodiments described herein, the modeling material formulation comprises at least one acrylate material, which is also referred to herein as Component C, and which is represented by Formula I:

[0271]

[0272] Formula I

[0273] wherein:

[0274] Ri and R2 are each independently hydrogen or alkyl (e.g., a lower alkyl of 1-6 or 1-4 carbon atoms);

[0275] Y is selected from O, S, NR3, and CR4R5, wherein R3, R4 and R5 are each independently selected from hydrogen and alkyl (e.g., a lower alkyl of 1-6 or 1-4 carbon atoms); and

[0276] Xi and X2 are each independently a substituted or unsubstituted alkylene of 1-4 carbon atoms in length, such that the total number of atoms of a backbone chain formed of Xi, Y and X2 is no more than 6. According to some embodiments of any of the embodiments described herein, Xi, Y and X2 are selected to as to favor (thermodynamically) a formation of a stable alicyclic or heteroalicyclic (depending on the nature of Y) ring of 5, 6, 7 or 8 carbon atoms during polymerization.

[0277] According to some embodiments of any of the embodiments described herein, the total number of carbon atoms in Xi and X2 is no more than 5.

[0278] According to some embodiments of any of the embodiments described herein, the total number of atoms of a backbone chain formed of Xi, Y and X2 is 3, 4, 5 or 6. According to some of any of the embodiments described herein, the total number of atoms of a backbone chain formed of Xi, Y and X2 is 3, 4 or 5. According to some of any of the embodiments described herein, the total number of atoms of a backbone chain formed of Xi, Y and X2 is 3 or 4. According to some of any of the embodiments described herein, the total number of atoms of a backbone chain formed of Xi, Y and X2 is 3.

[0279] According to some embodiments of any of the embodiments described herein, Y is O. When Y is O, the compound of Formula I is an a-(unsaturated alkoxyalkyl)acrylate.

[0280] According to some embodiments of any of the embodiments described herein, Y is O and Xi and X2 are each independently methylene, ethylene or propylene, each can be substituted or unsubstituted. When substituted, the alkylene (e.g., methylene, ethylene or propylene) can be substituted by one or more substituents, preferably substituents that do not interfere with the polymerization of the material, for example, alkyl substituents.

[0281] According to some embodiments of any of the embodiments described herein, Xi is methylene, which can be substituted or unsubstituted. According to some of any of the embodiments described herein, Xi is an unsubstituted methylene.

[0282] According to some embodiments of any of the embodiments described herein, X2 is methylene, which can be substituted or unsubstituted. According to some of any of the embodiments described herein, Xi is an unsubstituted methylene.

[0283] According to some embodiments of any of the embodiments described herein, Xi and X2 are each methylene (e.g., unsubstituted methylene).

[0284] According to some embodiments of any of the embodiments described herein, R2 is hydrogen.

[0285] According to some embodiments of any of the embodiments described herein, Ri is alkyl, such that the compound is an alkyl acrylate. According to some embodiments of any of the embodiments described herein, wherein Ri is a lower alkyl of 1, 2, 3 or 4 carbon atoms in length. According to some embodiments of any of the embodiments described herein, wherein Ri is an unsubstituted lower alkyl. According to some embodiments of any of the embodiments described herein, wherein Ri is methyl, for example, unsubstituted methyl.

[0286] An exemplary material usable as Component C according to some of the present embodiments is or comprises methyl 2-((allyloxy)methyl)acrylate. Other examples include, without limitation, ethyl 2-((allyloxy)methyl)acrylate; 2-((cyclohexenylmethoxy(methyl) acrylate; methyl 2-((l-butenoxy)methyl)acrylate; and methyl 2-((allyloxy)ethyl)acrylate.

[0287] According to some embodiments of any of the embodiments described herein, an amount of Component C is at least 10 %, or at least 15 %, or at least 18 %, or at least 20 %, by weight, and in some embodiments it ranges from 15 to 25, preferably from 18 to 22, or is about 20, % by weight, of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0288] As demonstrated in the Examples section that follows, formulations comprising lower amounts of Component C do not provide a hardened material that exhibits a toughness as described herein, whereby formulations comprising a higher amount of Component C may fail in meeting the process requirements.

[0289] According to some embodiments of any of the embodiments described herein, the formulation further comprises at least one additional curable material, preferably at least one, or at least two, multi-functional curable material.

[0290] According to some embodiments of any of the embodiments described herein, the formulation further comprises at least one multi-functional urethane (meth) acrylate featuring, when hardened, Tg higher than 80, or higher than 100 °C, which is also referred to herein as Component D.

[0291] According to some embodiments of any of the embodiments described herein, Component D is or comprises a multi-functional aliphatic (meth) acrylate featuring, when hardened, the indicated Tg.

[0292] According to some embodiments of any of the embodiments described herein, Component D is or comprises a di-functional (meth) acrylate featuring, when hardened, the indicated Tg.

[0293] According to some embodiments of any of the embodiments described herein, Component D is or comprises a di-functional aliphatic (meth) acrylate featuring, when hardened, the indicated Tg- According to some embodiments of any of the embodiments described herein, Component D is or comprises a urethane methacrylate featuring, when hardened the indicated Tg.

[0294] According to some embodiments of any of the embodiments described herein, Component D is or comprises an aliphatic urethane methacrylate featuring, when hardened the indicated Tg. According to some embodiments of any of the embodiments described herein, Component D features, when hardened, Tg of at least 100, or at least 120, °C.

[0295] According to some embodiments of any of the embodiments described herein, Component D is or comprises a di-functional aliphatic methacrylate featuring, when hardened, Tg of at least 100, or at least 120, °C.

[0296] Exemplary materials that are usable as Component D according to some embodiments of the present invention are those marketed under the tradenames Genomer 4297 and Genomer 4205, although any other multi-functional (e.g., di-functional) urethane (meth) acrylate materials that feature Tg as indicated are also contemplated.

[0297] According to some embodiments of any of the embodiments described herein, an amount of Component D is at least 5 % or at least 10 % by weight, or ranges from 5 to 25, or from 5 to 20, or from 10 to 25, or from 10 to 20, or from 10 to 15, % by weight, of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0298] According to some of any of the embodiments described herein, the formulation further comprises at least one multi-functional polyether (meth)acrylate material featuring, when hardened, Tg lower than 20, or lower than 0, °C, which is also referred to herein as Component E.

[0299] By “polyether” (meth)acrylate material, it is meant that the material features one or more of an oligomeric or polymeric chain of a polyether, namely, a chain that comprises at least one “-O-“ ether groups between two hydrocarbon groups such as alkylene. An exemplary polyether comprises one or more of an oligo(alkylene glycol) chain or a poly(alkylene glycol) chain, as these are defined herein.

[0300] According to some embodiments of any of the embodiments described herein, Component E has a molecular weight (MW) that is at least 500 grams / mol.

[0301] Herein throughout, whenever a MW is described in the context of oligomeric or polymeric materials, it refers to either Mn (number average molecular weight) or Mw (weight average molecular weight), typically to Mn. Material featuring the indicated MW can be identified according to the CAS number or the information provided by the manufacturer, or MW can be measured using methods known in the art, for example, GPC or SEC.

[0302] According to some embodiments of any of the embodiments described herein, Component E has a molecular weight (MW) that ranges from 500 grams / mol and up to 10,000 grams / mol, for example, from 500 to 10,000 or from 500 to 8,000, or from 500 to 6,000, or from 500 to 6,000, grams / mol, including any intermediate values and subranges therebetween.

[0303] The multi-functional polyether (meth) acrylate can be an acrylic material that comprises a polyether as defined herein or a urethane acrylate that comprises a polyether as defined herein. According to some embodiments of any of the embodiments described herein, Component E comprises a di-functional polyether (meth) acrylate which features, when hardened, Tg as indicated.

[0304] According to some embodiments of any of the embodiments described herein, Component E features, when hardened, Tg lower than 20, or lower than 10, preferably lower than 0, for example, in a ranges of from -100 to 0, or from -100 to 20, or from -60 to 0, or from -60 to 20, or from -60 to 0, or from -50 to 0 or from -50 to 20, or from -20 to 0 or from -20 to 20, or from -100 to -20, or from -100 to -10, or from -60 to -20, °C, including any intermediate values and subranges therebetween.

[0305] According to some embodiments of any of the embodiments described herein, Component E is or comprises a multi-functional (e.g., di-functional) aliphatic (meth)acrylate featuring a poly(alkylene glycol moiety), which is also referred to herein as Component E2.

[0306] According to some of these embodiments, the poly(alkylene glycol) moiety in Component E2 can be, for example, polypropylene glycol) moiety, poly(isopropylene glycol) moiety and / or poly(tetramethylene glycol) moiety, although any other poly(alkylene glycol) moieties are contemplated, as long as the material features Tg as indicated.

[0307] According to some embodiments of any of the embodiments described herein, Component E2 is or comprises a di-functional aliphatic acrylate featuring a poly(alkylene glycol moiety) (e.g., a polypropylene glycol) moiety, poly(isopropylene glycol) moiety or a poly(tetramethylene glycol) moiety).

[0308] According to some embodiments of any of the embodiments described herein, Component E2 has a molecular weight (MW) that is at least 500 grams / mol but is lower than 2,000 grams / mol or lower than 1,000 grams / mol.

[0309] According to some embodiments of any of the embodiments described herein, Component E2 is or comprises a di-functional aliphatic acrylate featuring a poly(alkylene glycol moiety) (e.g., a polypropylene glycol) moiety, poly(isopropylene glycol) moiety or a poly(tetramethylene glycol) moiety) featuring Tg lower than 0 °C, and molecular weight in a range of from 500 to 2000, or from 500 to 1000, grams / mol, including any intermediate values and subranges therebetween.

[0310] Exemplary materials usable as Component E2 include, without limitations, those marketed under the trade name A-PTMG-65 by Asahi Glass Co.

[0311] According to some embodiments of any of the embodiments described herein, Component E is or comprises a multi-functional (e.g., di-functional) polyether urethane (meth)acrylate, which is also referred to herein as Component El. According to some embodiments of any of the embodiments described herein, Component El is a multi-functional (e.g., di-functional) polyether urethane (meth)acrylate. According to some of these embodiments, Component El has MW higher than 2,000 or higher than 3,000 grams / mol, or higher than 5,000 grams / mol, for example, in a range of from 2,000 to 10,000 or from 2,000 to 8,000, or from 2,000 to 6,000, or from 3,000 to 10,000, or from 3,000 to 8,000, or from 3,000 to 6,000, or from 4,000 to 10,000, or from 4,000 to 8,000, or from 4,000 to 6,000, or from 5,000 to 10,000, or from 5,000 to 8,000 or from 5,000 to 6,000, or from 2,000 to 5,000, including any intermediate values and subranges therebetween.

[0312] According to some embodiments of any of the embodiments described herein, Component El is a di-functional poly ether urethane acrylate featuring Tg as indicated.

[0313] According to some embodiments of any of the embodiments described herein, Component El is a di-functional poly ether urethane acrylate featuring Tg and MW as indicated.

[0314] According to some embodiments of any of the embodiments described herein, the multifunctional (e.g., di-functional) polyether urethane (meth)acrylate Component El features a poly(alkylene glycol) moiety as described herein (e.g., a polypropylene glycol) moiety, poly (isopropylene glycol) moiety or a poly (tetramethylene glycol) moiety), as long as it features the Tg as indicated.

[0315] According to some embodiments of any of the embodiments described herein, Component E is or comprises Component El, which is a di-functional urethane acrylate featuring a poly(alkylene glycol) moiety (e.g., a polypropylene glycol) moiety, poly(isopropylene glycol) moiety or a poly(tetramethylene glycol) moiety) and having MW of at least 2,000, or at least 3,000 or at least 4,000 or at least 5,000 grams / mol, as described herein.

[0316] According to exemplary embodiments, Component El comprises a poly(alkylene glycol) moiety which is or comprises poly(isopropylene glycol).

[0317] Exemplary materials usable as Component El include, without limitations, materials marketed by Sartomer under the CN9000 series, for example, CN9002, a material marketed under the name Ebecryl 230, and similar materials.

[0318] According to some embodiments of any of the embodiments described herein, Component E is or comprises a multi-functional ethoxylated aromatic (meth)acrylate featuring at least 10 ethoxylated groups, which is also referred to herein as Component E3.

[0319] According to some embodiments of any of the embodiments described herein, Component E3 is or comprises a di-functional ethoxylated aromatic (meth)acrylate featuring at least 10 ethoxylated groups, as these are defined herein. In multifunctional materials, typically, each of the (meth) acrylate groups are linked to an alkylene glycol group or chain, and the alkylene glycol groups or chains are linked to one another through a branching unit, such as, for example, a branched alkyl, cycloalkyl, aryl (e.g., Bisphenol A), etc.

[0320] In some embodiments, the ethoxylated material comprises at least one, or at least two ethoxylated group(s)s, that is, at least one or at least two alkylene glycol moieties or groups. Some or all of the alkylene glycol groups can be linked to one another to form an alkylene glycol chain. For example, an ethoxylated material that comprises 30 ethoxylated groups can comprise a chain of 30 alkylene glycol groups linked to one another, two chains, each, for example, of 15 alkylene glycol moieties linked to one another, the two chains linked to one another via a branching moiety, or three chains, each, for example, of 10 alkylene glycol groups linked to one another, the three chains linked to one another via a branching moiety. Shorter and longer chains are also contemplated.

[0321] The ethoxylated material can comprise one, two or more alkylene glycol chains, of any length.

[0322] The term “branching unit” as used herein describes a multi-radical, preferably aliphatic or alicyclic group. By “multi-radical” it is meant that the unit has two or more attachment points such that it links between two or more atoms and / or groups or moieties.

[0323] In some embodiments, the branching unit is derived from a chemical moiety that has two, three or more functional groups. In some embodiments, the branching unit is a branched alkyl or a cycloalkyl (alicyclic) or an aryl (e.g., phenyl) as defined herein.

[0324] In exemplary embodiments, Component E3 features an aromatic branching unit, for example, bisphenol A, to which two chains of 10 or more ethoxylated groups altogether, each chain terminating by a (meth)acrylate group, are attached.

[0325] Exemplary materials usable as Component E3 include those marketed as Miramer 2100. According to exemplary embodiments, Component E in the formulations comprises Component El and / or Component E2, as these are described herein in any of the respective embodiments and any combination thereof. According to some embodiments, Component E comprises at least one of a multi-functional (e.g., di-functional) aliphatic (meth)acrylate featuring a poly(alkylene glycol moiety) (Component E2) and a multi-functional (e.g., di-functional) polyether urethane (meth)acrylate featuring MW higher than 2,000 or higher than 3,000 grams / mol (Component El).

[0326] According to some embodiments of any of the embodiments described herein, a total amount of Component E in the formulations ranges from 5 to 20, or from 5 to 15, or from 5 to 12, or from 8 to 20, or from 8 to 15, or from 8 to 12, % by weight, of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0327] According to some embodiments of any of the embodiments described herein, the formulation comprises Component C, Component D and Component E (e.g., Component El and / or Component E2), as these are described herein in any of the respective embodiments and any combination thereof.

[0328] According to some embodiments of any of the embodiments described herein, the formulation further comprises at least one mono-functional (meth) acrylate featuring, when hardened, Tg higher than 80, or higher than 100 °C, which is also referred to herein as Component A.

[0329] According to some embodiments of any of the embodiments described herein, Component A comprises at least one hydrophilic mono-functional (meth) acrylate featuring Tg as indicated, which is also referred to herein as Component Al.

[0330] According to some embodiments of any of the embodiments described herein, Component A comprises at least one hydrophilic mono-functional (meth) acrylate featuring Tg as indicated, which is also referred to herein as Component Al, and at least one hydrophobic mono-functional (meth)acrylate featuring Tg as indicated, which is also referred to herein as Component A2.

[0331] As used herein throughout, the term “hydrophilic” describes a physical property of a material or a portion of a material (e.g., a chemical group in a compound) which accounts for transient formation of bond(s) with water molecules, typically through hydrogen bonding.

[0332] Hydrophilic materials dissolve more readily in water than in oil or other hydrophobic solvents. Hydrophilic materials can be determined, for example, as having LogP lower than 0.5, when LogP is determined in octanol and water phases at room temperature.

[0333] Hydrophilic materials can alternatively, or in addition, be determined as featuring a lipophilicity / hydrophilicity balance (HLB), according to the Davies method, of at least 10, or of at least 12.

[0334] As used herein throughout, the term “amphiphilic” describes a property of a material that combines both hydrophilicity, as described herein for hydrophilic materials, and hydrophobicity or lipophilicity, as defined herein for hydrophobic materials.

[0335] Amphiphilic materials typically comprise both hydrophilic groups as defined herein and hydrophobic groups, as defined herein, and are substantially soluble in both water and a water-immiscible solvent (oil).

[0336] Amphiphilic materials can be determined by, for example, as having LogP of 0.8 to 1.2, or of about 1, when LogP is determined in octanol and water phases at room temperature. Amphiphilic materials can alternatively, or in addition, be determined as featuring a lipophilicity / hydrophilicity balance (HLB), according to the Davies method, of 3 to 12, or 3 to 9.

[0337] As used herein throughout, the term “hydrophobic” describes a physical property of a material or a portion of a material (e.g., a chemical group in a compound) which does not form bond(s) with water molecules. Hydrophobic materials dissolve more readily in oil than in water. Hydrophobic materials can be determined, for example, as having LogP higher than 1, preferably higher than 2, when LogP is determined in octanol and water phases.

[0338] A hydrophilic material or portion of a material (e.g., a chemical group in a compound) is one that is typically charge-polarized and capable of hydrogen bonding.

[0339] Amphiphilic materials typically comprise one or more hydrophilic groups (e.g., a charge-polarized group), in addition to hydrophobic groups.

[0340] Hydrophilic materials or groups, and amphiphilic materials, typically include one or more electron-donating heteroatoms which form strong hydrogen bonds with water molecules. Such heteroatoms include, but are not limited to, oxygen and nitrogen. Preferably, a ratio of the number of carbon atoms to a number of heteroatoms in a hydrophilic material or group is 10:1 or lower, and can be, for example, 8:1, more preferably 7:1, 6:1, 5:1 or 4:1, or lower. It is to be noted that hydrophilicity and amphiphilicity of materials and groups may result also from a ratio between hydrophobic and hydrophilic moieties in the material or chemical group, and does not depend solely on the above-indicated ratio.

[0341] A hydrophilic material can have one or more hydrophilic groups or moieties. Hydrophilic groups are typically polar groups, comprising one or more electron-donating heteroatoms such as oxygen and nitrogen.

[0342] Exemplary hydrophilic groups include, but are not limited to, an electron-donating heteroatom, a carboxylate, a thiocarboxylate, oxo (=0), a linear amide, hydroxy, a (Cl-4)alkoxy, an (Cl-4)alcohol, a heteroalicyclic (e.g., having a ratio of carbon atoms to heteroatoms as defined herein), a cyclic carboxylate such as lactone, a cyclic amide such as lactam, a carbamate, a thiocarbamate, a cyanurate, an isocyanurate, a thiocyanurate, urea, thiourea, an alkylene glycol (e.g., ethylene glycol or propylene glycol), and a hydrophilic polymeric or oligomeric moiety, as these terms are defined hereinunder, and any combinations thereof (e.g., a hydrophilic group that comprises two or more of the indicated hydrophilic groups).

[0343] In some embodiments, the hydrophilic group is, or comprises, an electron donating heteroatom, a carboxylate, a heteroalicyclic, an alkylene glycol and / or a hydrophilic oligomeric moiety. An amphiphilic moiety or group typically comprises one or more hydrophilic groups as described herein and one or more hydrophobic groups, or, can a heteroatom-containing group or moiety in which the ratio of number of carbon atoms to the number of heteroatoms accounts for amphiphilicity.

[0344] According to some embodiments of any of the embodiments described herein, Component Al is a mono-functional acrylate, that is hydrophilic, and is preferably water-soluble as described herein, which can be aliphatic or alicyclic. In exemplary embodiments, Component Al is a hydrophilic heteroalicyclic acrylate. An exemplary hydrophilic monomeric mono-functional acrylate is acryloyl morpholine (ACMO).

[0345] According to some embodiments of any of the embodiments described herein, Component A2 is a mono-functional acrylate, that is hydrophobic, which can be aliphatic or alicyclic. In exemplary embodiments, Component A2 is a hydrophobic alicyclic acrylate. An exemplary hydrophilic monomeric mono-functional acrylate is isobomyl acrylate (IBOA).

[0346] According to some embodiments of any of the embodiments described herein, a total amount of Component Al and Component A2 ranges from 10 to 50, or from 10 to 40, or from 10 to 30, or from 15 to 50, or from 15 to 45, or from 15 to 40, or from 15 to 30, or from 15 to 25, or from 20 to 25, % by weight of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0347] According to some embodiments of any of the embodiments described herein, a total amount of Component Al ranges from 10 to 30, or from 10 to 25, or from 15 to 25, % by weight of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0348] According to some embodiments of any of the embodiments described herein, a weight ratio between Component Al and A2 is one of the parameters that determined the transparency or opacity of the formulation.

[0349] According to some embodiments of any of the embodiments described herein, a weight ratio between Component Al and A2 is at least 1:1 or at least 1.5:1 or at least 2:1.

[0350] According to some embodiments of any of the embodiments described herein, the formulation comprises at least Component C, Component D and Component E (e.g., Component El and / or Component E2), and Component Al, as these are described herein in any of the respective embodiments and any combination thereof.

[0351] According to some of these embodiments, the formulations further comprises Component A2, as described herein. According to some embodiments of any of the embodiments described herein, the formulation further comprises one or more of a mono-functional (meth) acrylate and a multifunctional (meth)acrylate, for example, one or more of Component B, Component F and Component G, as these are described herein. Typically, but not obligatory, these additional materials are added so as to impart to the formulation reactivity, toughness, and / or hardness, and / or to improve its viscosity and / or the surface properties of the hardened material. Typically, but not obligatory, these additional materials feature, when hardened, medium Tg, that is, in a range of from 0 to 80, or from 0 to 50, °C.

[0352] According to some embodiments of any of the embodiments described herein, the formulation further comprises at least one mono-functional (meth) acrylate featuring, when hardened, Tg of up to 80 ° C, e.g., in a range of from 0 to 80, or from 0 to 50, °C, including an intermediate values and subranges therebetween, which is referred to herein as Component B.

[0353] Component B can comprise any mono-functional (meth) acrylate that features the indicated Tg, which can be hydrophilic, hydrophobic or amphiphilic.

[0354] In exemplary embodiments, Component B is a hydrophobic mono-functional (meth)acrylate featuring the indicated Tg, and is referred to herein as Component Bl. An exemplary such material is marketed under the tradename SR789, although any other materials are contemplated.

[0355] In exemplary embodiments, Component B comprises an epoxy-type mono-functional (meth)acrylate featuring the indicated Tg, and is also referred to herein as Component B2.

[0356] Herein throughout, the phrase “epoxy-type” with respect to a curable material describes a material featuring a curable group (e.g., a (meth) acrylate group as defined herein) and one or more groups derived from epoxide, for example, a -O-CH2-CH2-CH(OH)- group. Epoxy type materials can be monomeric, oligomeric or polymeric curable materials. In some embodiments, epoxy-type curable materials polymerize and / or crosslink by radical polymerization, as described herein. An exemplary material is marketed under the tradename DA- 141.

[0357] According to some embodiments of any of the embodiments described herein, the formulation further comprises at least one at least one multi-functional (meth)acrylate featuring, when hardened, Tg of up to 80, or in a range of from 0 to 80, °C (Component F).

[0358] According to some embodiments of any of the embodiments described herein, Component F has a MW higher than 500, or higher than 1,000, or in range of from 1,000 to 2,000, grams / mol, including any intermediate values and subranges therebetween.

[0359] According to some embodiments of any of the embodiments described herein, Component F is a multi-functional (e.g., di-functional) urethane (meth)acrylate (e.g., acrylate) featuring, when hardened, the indicated Tg and having a MW lower than 2,000 grams / mol, which is also referred to herein as Component F2.

[0360] According to some embodiments of any of the embodiments described herein, Component F2 has MW in a range of from 200 to 2,000, or from 500 to 2,000, or from 200 to 1,800, or from 500 to 1,800, or from 1,000 to 2,000, or from 1,000 to 1,800, or from 1,200 to 1,800, grams / mol, including any intermediate values and subranges therebetween.

[0361] According to some embodiments of any of the embodiments described herein, Component F2 features, when hardened, Tg lower than 50, or lower than 20, or in a range of from 0 to 50 or from 0 to 50, or 0 to 40, or 0 to 30, or 0 to 20, °C, including any intermediate values and subranges therebetween.

[0362] According to some embodiments of any of the embodiments described herein, Component F is a di-functional urethane acrylate featuring, when hardened, Tg in a range of from 0 to 50 or from 0 to 50, or 0 to 40, or 0 to 30, or 0 to 20, °C and having a MW in a range of from 500 to 1,800 or from 1,000 to 1,800, or from 1,200 to 1,800 grams / mol, including any intermediate values and subranges therebetween.

[0363] An exemplary material usable as Component F2 is marketed under the tradename CN991, although any other materials featuring the properties as indicated are contemplated.

[0364] According to some embodiments of any of the embodiments described herein, an amount of Component F2, if present, ranges from 5 to 30, or from 10 to 30, or from 10 to 25, or from 15 to 30, or from 10 to 20, % by weight of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0365] According to some embodiments of any of the embodiments described herein, Component F comprises at least one epoxy-type multi-functional (meth)acrylate, which is also referred to herein as Component Fl.

[0366] According to some embodiments of any of the embodiments described herein, Component Fl is an epoxy-type multi-functional, preferably di-functional, acrylate.

[0367] According to some embodiments of any of the embodiments described herein, Component Fl features, when hardened, Tg higher than 50, or in a range of from 50 to 80, °C, including any intermediate values and subranges therebetween.

[0368] According to some embodiments of any of the embodiments described herein, Component Fl has MW in a range of from 200 to 2,000, or from 500 to 2,000, or from 200 to 1,800, or from 500 to 1,800, or from 1,000 to 2,000, or from 1,000 to 1,800, or from 1,200 to 1,800, grams / mol, including any intermediate values and subranges therebetween. According to some embodiments of any of the embodiments described herein, Component Fl is an epoxy-type multi-functional, preferably di-functional, acrylate that features, when hardened, Tg higher than 50, or in a range of from 50 to 80, °C, including any intermediate values and subranges therebetween, and has MW in a range of from 200 to 2,000, or from 500 to 2,000, or from 200 to 1,800, or from 500 to 1,800, or from 1,000 to 2,000, or from 1,000 to 1,800, or from 1,200 to 1,800, grams / mol, including any intermediate values and subranges therebetween.

[0369] As exemplary material usable as Component Fl is marketed under the tradename Genomer 2281, although any other materials are contemplated.

[0370] According to some embodiments of any of the embodiments described herein, an amount of Component Fl, if present, ranges from 5 to 20, or from 5 to 15, or from 10 to 15, % by weight, of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0371] According to some embodiments of any of the embodiments described herein, Component F comprises at least one multi-functional (e.g., di-functional) urethane (meth) acrylate (e.g., acrylate) featuring, when hardened, Tg as indicated and having a MW higher than 2,000 grams / mol, which is also referred to herein as Component F3.

[0372] According to some embodiments of any of the embodiments described herein, Component F3 features, when hardened, Tg in a range of from 0 to 50, or from 10 to 50, or from 20 to 50, or from 30 to 50, or from 40 to 50 °C, including any intermediate values and subranges therebetween.

[0373] According to some embodiments of any of the embodiments described herein, Component F3 has MW in a range of from 2,000 to 5,000, or from 2,000 to 4,000, or from 2,000 to 3,000 or from 3,000 to 4,000, grams / mol, including any intermediate values and subranges therebetween.

[0374] According to some embodiments of any of the embodiments described herein, Component F3 features, when hardened, Tg in a range of from 0 to 50, or from 10 to 50, or from 20 to 50, or from 30 to 50, or from 40 to 50 °C, including any intermediate values and subranges therebetween, and MW in a range of from 2,000 to 5,000, or from 2,000 to 4,000, or from 2,000 to 3,000 or from 3,000 to 4,000, grams / mol, including any intermediate values and subranges therebetween.

[0375] Exemplary materials usable as Component F3 include, without limitation, those marketed under the tradenames CN 1970EU and PU256NT.

[0376] According to some embodiments of any of the embodiments described herein, an amount of Component F3, if present, ranges from 1 to 10, or from 3 to 8, or from 3 to 5, % by weight, of the total weight of the formulation, including any intermediate values and subranges therebetween. According to some embodiments of any of the embodiments described herein, Component F comprises a tri-functional urethane (meth) acrylate featuring, when hardened the indicated Tg and having MW higher than 2,000 grams / mol, which is also referred to herein as Component F4.

[0377] According to some embodiments of any of the embodiments described herein, Component F4 has MW in a range of from 2,000 to 5,000, or from 3,000 to 5,000, or from 3,500 to 5,000 or from 3,500 to 4,500, grams / mol, including any intermediate values and subranges therebetween.

[0378] According to some embodiments of any of the embodiments described herein, Component F4 features, when hardened, Tg in a range of from 0 to 50, or from 10 to 50, or from 10 to 40, or from 10 to 30, or from 20 to 30, or from 0 to 40, or from 0 to 30, °C, including any intermediate values and subranges therebetween.

[0379] According to some embodiments of any of the embodiments described herein, Component F4 has MW in a range of from 2,000 to 5,000, or from 3,000 to 5,000, or from 3,500 to 5,000 or from 3,500 to 4,500, grams / mol, including any intermediate values and subranges therebetween, and features, when hardened, Tg in a range of from 0 to 50, or from 10 to 50, or from 10 to 40, or from 10 to 30, or from 20 to 30, or from 0 to 40, or from 0 to 30, °C, including any intermediate values and subranges therebetween.

[0380] An exemplary material usable as Component F4 is marketed under the tradename BR990. According to some embodiments of any of the embodiments described herein, an amount of Component F4, if present, ranges from 1 to 5, or from 1 to 3, % by weight, of the total weight of the formulation.

[0381] According to some embodiments of any of the embodiments described herein, the formulation comprises one or more of Components Fl, F2, F3 and F4.

[0382] According to some embodiments of any of the embodiments described herein, the formulation comprises at least: Component A, in a total amount of from 15 to 25 % by weight of the total weight of the formulation; Component C, in a total amount of from 17 to 23, or of about 20, % by weight of the total weight of the formulation; Component D, in a total amount of from 10 to 30, or from 10 to 20, % by weight, of the total weight of the formulation; and Component E, in a total amount of from 5 to 15, % by weight of the total weight of the formulation.

[0383] According to some of these embodiments, the formulation further comprises one or more of Component Bl, B2, Fl, F2 and F3.

[0384] According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises a dispersant (Component H).

[0385] According to some of these embodiments, the dispersant features curable groups, preferably (meth)acrylic groups, and is also referred to herein as Component Hl. According to some embodiments of any of the embodiments described herein, Component Hl is a multi-functional (e.g., di-functional) polyester silicon (meth)acrylate.

[0386] According to some embodiments of any of the embodiments described herein, Component Hl is a di-functional polyester silicon (meth)acrylate.

[0387] According to some embodiments of any of the embodiments described herein, Component Hl is a multi-functional (e.g., di-functional) polyester silicon acrylate.

[0388] According to some embodiments of any of the embodiments described herein, Component Hl is a di-functional polyester silicon acrylate.

[0389] According to some embodiments of any of the embodiments described herein, Component Hl has an average MW of at least 1,000, or at least 2,000, or at least 3,000 grams / mol, for example, in a range of from 1,000 to 10,000, or 2,000 to 10,000, or 3,000 to 10,000, or 1,000 to 8,000, or 2,000 to 8,000 or 3,000 to 8,000, including any intermediate values and subranges therebetween, and is considered as an oligomeric material.

[0390] According to some embodiments of any of the embodiments described herein, Component Hl is a multi-functional (e.g., di-functional) polyester silicon (meth)acrylate, having an average MW of at least 1,000 grams / mol as described herein.

[0391] According to some embodiments of any of the embodiments described herein, Component Hl is a di-functional polyester silicon (meth)acrylate, having an average MW of at least 1,000 grams / mol as described herein.

[0392] According to some embodiments of any of the embodiments described herein, Component Hl is a multi-functional (e.g., di-functional) polyester silicon acrylate, having an average MW of at least 1,000 grams / mol as described herein.

[0393] According to some embodiments of any of the embodiments described herein, Component Hl is a di-functional polyester silicon acrylate, having an average MW of at least 1,000 grams / mol as described herein.

[0394] According to some embodiments of any of the embodiments described herein, Component Hl features, when hardened, low Tg, preferably lower than 0, or lower than -20, or lower than -50, °C.

[0395] According to some embodiments of any of the embodiments described herein, an amount of Component Hl ranges from 0.1 to 2, or from 0.1 to 1.5, or from 0.5 to 1.5, or from 0.5 to 2, or is about 1, % by weight, of the total weight of the formulation, including any intermediate values and subranges therebetween. According to some embodiments of any of the embodiments described herein, the dispersant comprises a non-curable dispersant, which is also referred to as Component H2. Exemplary such dispersants include those marketed as BYK family.

[0396] According to some embodiments of any of the embodiments described herein, an amount of Component H2 ranges from 0.01 to 1, or from 0.01 to 0.5, or from 0.1 to 1, or from 0.2 to 0.5, % by weight, of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0397] According to some embodiments of any of the embodiments described herein, the formulation comprises both Components Hl and H2.

[0398] According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises a polymerization inhibitor (Component I), as described herein, for example, a phenol-type inhibitor or any other inhibitor that is commonly used in medical devices or applications and / in food products.

[0399] According to some embodiments of any of the embodiments described herein, an amount of the inhibitor ranges from 0.001 to 0.010, % by weight, of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0400] According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises at least one photoinitiator (Component J).

[0401] According to some embodiments of any of the embodiments described herein, an amount of the photoinitiator ranges from 1 to 5, or from 1 to 4, or from 1 to 3, or from 2 to 4, % by weight of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0402] According to some embodiments of any of the embodiments described herein, the photoinitiator(s) comprises, or consists essentially of, a phosphine oxide-type (e.g., mono-acrylated (MAPO) or bis-acrylated phosphine oxide-type (BAPO) photoinitiator.

[0403] Exemplary monoacyl and bisacyl phosphine oxides include, but are not limited to, 2,4,6-trimethylbenzoyldiphenyl phosphine oxide, bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide, dibenzoylphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)phenyl phosphine oxide, tris(2,4-dimethylbenzoyl) phosphine oxide, tris(2-methoxybenzoyl)phosphine oxide, 2,6-dimethoxybenzoyldiphenyl phosphine oxide, 2,6-dichlorobenzoyldiphenyl phosphine oxide, 2,3,5,6-tetramethylbenzoyldiphenyl phosphine oxide, benzoyl-bis(2,6-dimethylphenyl) phosphonate, and 2,4,6-trimethylbenzoylethoxyphenyl phosphine oxide. Commercially available phosphine oxide photoinitiators capable of free-radical initiation when irradiated at wavelength ranges of greater than about 380 nm to about 450 nm include 2,4,6-trimethylbenzoyldiphenyl phosphine oxide (TPO), bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide (marketed as IRGACURE® 819), bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylpentyl) phosphine oxide (marketed as CGI 403), a 25:75 mixture, by weight, of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide and 2-hydroxy-2-methyl-l-phenylpropan-l-one (marketed as IRGACURE® 1700), a 1:1 mixture, by weight, of bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide and 2-hydroxy-2-methyl-l -phenylpropane- 1 -one (marketed as DAROCUR® 4265), and ethyl 2,4,6-trimethylbenzylphenyl phosphinate (LUCIRIN LR8893X).

[0404] In an exemplary embodiment, the photoinitiator is or comprises bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide (marketed as IRGACURE® 819).

[0405] In an exemplary embodiment, the photoinitiator Component J comprises two or more types of the photoinitiators as described herein.

[0406] According to some embodiments of any of the embodiments described herein, the modeling material formulation is a clear (e.g., transparent), colorless formulation, which is devoid of a coloring agent.

[0407] According to some embodiments of any of the embodiments described herein, the modeling material formulation further comprises one or more coloring agent(s) or pigments, which are referred to herein as Component P.

[0408] The coloring agent can be a pigment or a dye and is preferably a pigment.

[0409] The pigments can be organic and / or inorganic and / or metallic pigments, and in some embodiments the pigments are nanoscale pigments, which include nanoparticles.

[0410] Exemplary inorganic pigments include nanoparticles of titanium oxide, and / or of zinc oxide and / or of silica. Exemplary organic pigments include nano-sized carbon black.

[0411] In some embodiments, combinations of white and color pigments are used to prepare colored cured materials.

[0412] According to some embodiments of any of the embodiments described herein, the coloring agent comprises a mixture of a pigment and at least one (meth)acrylic material, for example, a mixture of mono-functional and multi-functional (meth) acrylate materials, such that the pigment is introduced to the formulation within this mixture.

[0413] According to some embodiments of any of the embodiments described herein, the pigment is a white pigment and the formulation provides a white hardened material.

[0414] According to some embodiments of any of the embodiments described herein, the coloring agent comprises a mixture of a white pigment and one or more curable materials such as (meth)acrylic materials, such that the pigment is introduced to the formulation within this mixture. According to some of these embodiments, an amount of the white pigment in the mixture ranges from 20 to 50 % by weight of the total weight of the mixture, including any intermediate values and subranges therebetween.

[0415] According to some of these embodiments, an amount of the coloring agent, which is a mixture of a white pigment and at least one (meth)acrylic material ranges from 1 to 20, or from 5 to 20, or from 5 to 15, % by weight of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0416] According to some embodiments of any of the embodiments described herein, the coloring agent comprises a mixture of a pigment and at least one (meth)acrylic material, for example, a mixture of mono-functional and multi-functional (meth) acrylate materials, such that the pigment is introduced to the formulation within this mixture.

[0417] According to some embodiments of any of the embodiments described herein, the pigment is a black pigment (e.g., carbon black) and the formulation provides a black hardened material.

[0418] According to some embodiments of any of the embodiments described herein, the coloring agent comprises a mixture of a black pigment and one or more curable materials such as (meth)acrylic materials, such that the pigment is introduced to the formulation within this mixture.

[0419] According to some of these embodiments, an amount of the black pigment in the mixture ranges from 1 to 50 % by weight of the total weight of the mixture, including any intermediate values and subranges therebetween.

[0420] According to some of these embodiments, an amount of the coloring agent, which is a mixture of a black pigment and at least one (meth)acrylic material ranges from 0.01 to 1, or from 0.01 to 0.5, or from 0.05 to 0.5, % by weight of the total weight of the formulation, including any intermediate values and subranges therebetween.

[0421] According to some embodiments of any of the embodiments described herein, the pigment is a cyan pigment and the formulation provides a cyan hardened material.

[0422] According to some embodiments of any of the embodiments described herein, the coloring agent comprises a mixture of a cyan pigment and one or more curable materials such as (meth)acrylic materials, such that the cyan pigment is introduced to the formulation within this mixture.

[0423] According to some of these embodiments, an amount of the cyan pigment in the mixture ranges from 0.01 to 1, or from 0.05 to 0.5, or from 0.1 to 0.2, % by weight of the total weight of the mixture.

[0424] According to some embodiments of any of the embodiments described herein, the pigment is a yellow pigment and the formulation provides a yellow hardened material. According to some embodiments of any of the embodiments described herein, the coloring agent comprises a mixture of a yellow pigment and one or more curable materials such as (meth)acrylic materials, such that the yellow pigment is introduced to the formulation within this mixture.

[0425] According to some of these embodiments, an amount of the yellow pigment in the mixture ranges from 0.01 to 1, or from 0.05 to 0.5, or from 0.1 to 0.2, % by weight of the total weight of the mixture, including any intermediate values and subranges therebetween.

[0426] According to some embodiments of any of the embodiments described herein, the pigment is a magenta pigment and the formulation provides a magenta hardened material.

[0427] According to some embodiments of any of the embodiments described herein, the coloring agent comprises a mixture of a magenta pigment and one or more curable materials such as (meth)acrylic materials, such that the magenta pigment is introduced to the formulation within this mixture.

[0428] According to some of these embodiments, an amount of the magenta pigment in the mixture ranges from 0.01 to 1, or from 0.05 to 0.5, or from 0.1 to 0.2, % by weight of the total weight of the mixture, including any intermediate values and subranges therebetween.

[0429] According to some embodiments of any of the embodiments described herein, the formulation comprises one or more of a white, magenta, cyan, and yellow coloring agents, and in some of these embodiments, each pigment is introduced to the formulation in a mixture with curable materials as described herein.

[0430] According to some embodiments of any of the embodiments described herein, the modeling material formulation comprises Components H, I, and J, as described herein in any of the respective embodiments. According to some embodiments of any of the embodiments described herein, the modeling material formulation comprises Components H, I, J and P, as described herein in any of the respective embodiments. An exemplary such formulation is a white formulation that comprises a white pigment as described herein.

[0431] According to some embodiments of any of the embodiments described herein, the modeling material formulation comprises Components H, I, and J, as described herein in any of the respective embodiments, and is a transparent, optionally clear, colorless formulation.

[0432] According to some of these embodiments, the formulation further comprises a transparent pigment or dye (e.g., cyan, yellow, magenta), and is a transparent colored formulation.

[0433] According to some embodiments of any of the embodiments described herein, the modeling material formulation is a transparent formulation (which provides a transparent hardened material), for example, a colorless transparent formulation (which provides a colorless, clear, hardened material).

[0434] According to some embodiments of any of the embodiments described herein, an exemplary modeling material formulation which can provide a transparent hardened material as described herein comprises:

[0435] Component Al, in a total amount of from 15 to 20, % by weight, of the total weight of the formulation; Component A2, in a total amount of from 5 to 10, % by weight, of the total weight of the formulation; Component F3, in a total amount of from 3 to 8, % by weight, of the total weight of the formulation; Component C in an amount of from 15 to 25, or from 18 to 22, or of about 20 % by weight, of the total weight of the formulation; Component D, in an amount of from 15 to 25, or from 18 to 22, % by weight, of the total weight of the formulation; Component F2, in an amount of from 10 to 15, or from 18 to 22, % by weight, of the total weight of the formulation; Component E2, in an amount of from 5 to 10, % by weight, of the total weight of the formulation; and Component El, in an amount of from 1 to 5, or from 3 to 5, % by weight, of the total weight of the formulation.

[0436] According to some embodiments, this formulation further comprises: at least one photoinitiator (Component J) in a total amount of from 1 to 3, or from 2 to 3, % by weight, of the total weight of the formulation; at least one dispersant that features curable groups (Component Hl) in a total amount of about 1 % by weight of the total weight of the formulation; and at least one non-curable dispersant (Component H2) in a total amount of from 0.1 to 1 % by weight of the total weight of the formulation.

[0437] According to some embodiments of any of the embodiments described herein, an exemplary modeling material formulation which can provide a transparent hardened material as described herein comprises: Component Al, in a total amount of from 15 to 25, or from 18 to 22, % by weight, of the total weight of the formulation; Component A2, in a total amount of from 0.1 to 1, % by weight, of the total weight of the formulation; Component F3, in a total amount of from 5 to 20, or from 5 to 15, % by weight, of the total weight of the formulation; Component C in an amount of from 20 to 25, % by weight, of the total weight of the formulation; Component D, in an amount of from 10 to 15, % by weight, of the total weight of the formulation; Component E2, in an amount of from 8 to 12, % by weight, of the total weight of the formulation; and Component Fl, in an amount of from 15 to 20, % by weight, of the total weight of the formulation.

[0438] According to some embodiments, this formulation further comprises: at least one photoinitiator (Component J) in a total amount of from 1 to 2, % by weight, of the total weight of the formulation; and at least one non-curable dispersant (Component H2) in a total amount of from 0.1 to 1 % by weight of the total weight of the formulation.

[0439] According to some embodiments of any of the embodiments described herein, the modeling material formulation is an opaque formulation (which provides an opaque hardened material), for example, a white formulation (which provides a white hardened material).

[0440] According to some embodiments of any of the embodiments described herein, an exemplary modeling material formulation which can provide a white material as described herein comprises: Component Al, in a total amount of from 15 to 25, % by weight, of the total weight of the formulation; Component B2, in a total amount of from 3 to 8, % by weight, of the total weight of the formulation; Component C in an amount of from 15 to 25, or from 18 to 22, or of about 20 % by weight, of the total weight of the formulation; Component D, in an amount of from 10 to 15, or from 18 to 22, % by weight, of the total weight of the formulation; Component F2, in an amount of from 10 to 20, or from 13 to 18, % by weight, of the total weight of the formulation; and Component El, in an amount of from 5 to 10, % by weight, of the total weight of the formulation.

[0441] According to some of these embodiments, the formulation further comprises at least one photoinitiator (Component J) in a total amount of from 1 to 5, or of about 3, % by weight, of the total weight of the formulation; at least one dispersant that features curable groups (Component Hl) in a total amount of about 1 % by weight of the total weight of the formulation; and at least one non-curable dispersant (Component H2) in a total amount of from 0.1 to 1 % by weight of the total weight of the formulation.

[0442] According to some embodiments of any of the embodiments described herein, the modeling material formulation is an opaque formulation (which provides an opaque hardened material), for example, a colored formulation (which provides a colored hardened material).

[0443] According to some embodiments of any of the embodiments described herein, the modeling material formulation is a black formulation (which provides a black hardened material).

[0444] According to exemplary embodiments, such a formulation comprises: Component Al, in a total amount of from 15 to 25, % by weight, of the total weight of the formulation; Component A2, in a total amount of from 5 to 10, % by weight, of the total weight of the formulation; Component Bl, in a total amount of from 15 to 20, % by weight, of the total weight of the formulation; Component C in an amount of from 15 to 25, or from 18 to 22, or of about 20 % by weight, of the total weight of the formulation; Component D, in an amount of from 10 to 15, or from 28 to 22, % by weight, of the total weight of the formulation; Component El, in an amount of from 5 to 15, or from 8 to 12, or of about 10, % by weight, of the total weight of the formulation; and Component Fl, in an amount of from 10 to 15, % by weight, of the total weight of the formulation. According to exemplary embodiments, such a formulation comprises: Component Al, in a total amount of from 20 to 30, or of about 25, % by weight, of the total weight of the formulation; Component F3, in a total amount of from 10 to 20, or of about 15, % by weight, of the total weight of the formulation; Component C in an amount of about 20 % by weight, of the total weight of the formulation; Component D, in an amount of from 10 to 15, or from 28 to 22, % by weight, of the total weight of the formulation; Component El, in an amount of from 5 to 15, or from 8 to 12, or of about 11, % by weight, of the total weight of the formulation; and Component Fl, in an amount of from 10 to 15, % by weight, of the total weight of the formulation.

[0445] According to these exemplary embodiments, a black formulation further comprises at least one photoinitiator (Component J) in a total amount of from 1 to 3, or of about 2, % by weight, of the total weight of the formulation; at least one dispersant that features curable groups (Component Hl) in a total amount of about 1 % by weight of the total weight of the formulation; at least one non-curable dispersant (Component H2) in a total amount of from 0.1 to 1 % by weight of the total weight of the formulation; and at least one black coloring agent (e.g., as a mixture with (meth)acrylates) (Component P2), in an amount of from 0.1-0.2 % by weight of the total weight of the formulation.

[0446] According to exemplary embodiments, the modeling material formulation is a black formulation (which provides a black hardened material), and comprises Component Al, in a total amount of from 10 to 25, or from 10 to 20, or from 15 to 20, % by weight, of the total weight of the formulation; Component A2, in a total amount of from 5 to 10, % by weight, of the total weight of the formulation; Component C in an amount of from 18 to 22, or of about 20, % by weight, of the total weight of the formulation; Component D, in an amount of from 15 to 30, or from 20 to 30, or from 20-25, % by weight, of the total weight of the formulation; and Component El, in an amount of from 5 to 15, or from 8 to 12, or of about 10, % by weight, of the total weight of the formulation.

[0447] According to some of these embodiments, the formulation further comprises at least one photoinitiator (Component J) in a total amount of from 1 to 3, or of about 2, % by weight, of the total weight of the formulation; at least one dispersant that features curable groups (Component Hl) in a total amount of about 1 % by weight of the total weight of the formulation; at least one non-curable dispersant (Component H2) in a total amount of from 0.1 to 1 % by weight of the total weight of the formulation; and at least one colorant in a form of a (e.g., black) dye / pigment in a mixture of curable materials (Component P2), in an amount of from 0.1-0.2 % by weight of the total weight of the formulation. Kits:

[0448] In some embodiments of any of the embodiments described herein there is provided a kit comprising one or more of the formulations as described herein in any of the respective embodiments and any combination thereof.

[0449] In some embodiments of any of the embodiments described herein there is provided a kit comprising two or more formulations as described herein in any of the respective embodiments and any combination thereof. In some of these embodiments, each formulation is packaged individually in the kit.

[0450] In some embodiments of any of the embodiments described herein there is provided a kit comprising two or more formulations as described herein in any of the respective embodiments and any combination thereof, which differ from one another by the presence or absence, or type, of the coloring agent, and / or by its transparency. For example, the kit can comprise two or more transparent formulations, as described herein, each comprising a different coloring agent, for example, cyan, yellow, white or black. The kit can, for example, include a series of transparent formulations of different colors. The kit can alternatively comprise a set of opaque formulations, of different colors, optionally in addition to one or more transparent formulation(s). The kit can alternatively comprise, for example, two formulations of the same color, one being transparent and the other opaque. All according to any of the respective embodiments as described herein.

[0451] In some embodiments of any of the embodiments described herein, the kit further comprises one or more modeling material formulation(s), which is different from the formulation as described herein, for example, is characterized by a lower impact resistance.

[0452] In exemplary embodiments, the formulations are packaged within the kit in a suitable packaging material, preferably, an impermeable material (e.g., water- and gas-impermeable material), and further preferably an opaque material. In some embodiments, the kit further comprises instructions to use the formulations in an additive manufacturing process, preferably a 3D inkjet printing process as described herein. The kit may further comprise instructions to use the formulations in the process in accordance with the method as described herein.

[0453] Objects:

[0454] According to some embodiments of the present invention, there is provided a three-dimensional object obtained by an additive manufacturing process as described herein, using at least one formulation as described herein in any of the respective embodiments and any combination thereof.

[0455] According to some embodiments of any of the embodiments described herein, the three-dimensional object comprises in at least a portion thereof a hardened material that exhibits impact resistance (Izod XY notched impact resistance) of at least 40 J / m, or at least 50 L / mol, as described herein in any of the respective embodiments and any combination thereof.

[0456] According to some embodiments of any of the embodiments described herein, the three-dimensional object is further characterized by one, two, three of all of:

[0457] HDT (ASTM D648), as described and defined herein, higher than 50 °C (e.g., 50-60 °C); Tensile Strength (ASTM D638), as described and defined herein, of at least 30, or of from about 30 to 50, MPa;

[0458] Elongation at break (ASTM D638), as described and defined herein, of at least 25 %, or from about 25 to about 60, or from about 25 to about 50, or from about 25 to about 45, or from about 25 to about 40, %;

[0459] Flexural Strength (ASTM D790), as described and defined herein, of at least 40, or from about 40 to about 60, MPa; and Flexural Modulus (ASTM D790), as described and defined herein, of at least 1200, or from about 1200 to about 1800, MPa.

[0460] According to some embodiments of any of the embodiments described herein, the three-dimensional object is further characterized as exhibiting, in at least a portion thereof, Izod unnotched ZX impact resistance, as described and defined herein, which is higher than 100, preferably higher than 120. In exemplary embodiments, for an object manufactured in a matte mode as described herein, the object exhibits, in at least a portion thereof, Izod un-notched ZX impact resistance of, for example, 100-300, or 100-250, or 100-220, or 120-300, or 120-250, or 120-220, J / m. In exemplary embodiments, for an object manufactured in a glossy mode as described herein, the object exhibits, in at least a portion thereof, Izod un-notched ZX impact resistance of, for example, 200-1200, or 500-1200, or 800-1200, J / m.

[0461] According to some embodiments of any of the embodiments described herein, the three-dimensional object is further characterized by water absorption, as described and defined herein, of a 60x60x1 mm cube lower than 10 %, or lower than 8 %, or lower than 5 %, or lower than 3 %, or lower than 2, %, e.g., of 1-1.5 % (ASTM D 570-98).

[0462] According to some embodiments of any of the embodiments described herein, the three-dimensional object is further characterized by minimal Creep (at 70 % humidity and 40 °C), as defined herein.

[0463] As used herein the term “about” refers to ± 10 % or ± 5 %.

[0464] The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to".

[0465] The term “consisting of’ means “including and limited to”. The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

[0466] As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

[0467] Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0468] Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging / ranges between” a first indicate number and a second indicate number and “ranging / ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

[0469] Herein the terms "method" and “process” are used interchangeably and refer to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.

[0470] Herein throughout, whenever the phrase “weight percent”, or “% by weight” or “% wt.”, is indicated in the context of embodiments of a formulation (e.g., a modeling formulation), it is meant weight percent of the total weight of the respective uncured formulation.

[0471] Herein throughout, an acrylic material is used to collectively describe material featuring one or more acrylate, methacrylate, acrylamide and / or methacrylamide group(s).

[0472] Similarly, an acrylic group is used to collectively describe curable groups which are acrylate, methacrylate, acrylamide and / or methacrylamide group(s), preferably acrylate or methacrylate groups (referred to herein also as (meth)acrylate groups). Herein throughout, the term “(meth) acrylic” encompasses acrylic and methacrylic materials.

[0473] Whenever (meth)acrylate materials are described, it is to be noted that corresponding (meth)acrylamides are also contemplated, provided that they feature the indicated properties.

[0474] Herein throughout, the phrase “linking moiety” or “linking group” describes a group that connects two or more moieties or groups in a compound. A linking moiety is typically derived from a bi- or tri-functional compound, and can be regarded as a bi- or tri-radical moiety, which is connected to two or three other moieties, via two or three atoms thereof, respectively.

[0475] Exemplary linking moieties include a hydrocarbon moiety or chain, optionally interrupted by one or more heteroatoms, as defined herein, and / or any of the chemical groups listed below, when defined as linking groups.

[0476] When a chemical group is referred to herein as “end group” it is to be interpreted as a substituent, which is connected to another group via one atom thereof.

[0477] Herein throughout, the term “hydrocarbon” collectively describes a chemical group composed mainly of carbon and hydrogen atoms. A hydrocarbon can be comprised of alkyl, alkene, alkyne, aryl, and / or cycloalkyl, each can be substituted or unsubstituted, and can be interrupted by one or more heteroatoms. The number of carbon atoms can range from 2 to 30, and is preferably lower, e.g., from 1 to 10, or from 1 to 6, or from 1 to 4. A hydrocarbon can be a linking group or an end group.

[0478] Bisphenol A is an example of a hydrocarbon comprised of 2 aryl groups and one alkyl group. Dimethylenecyclohexane is an example of a hydrocarbon comprised of 2 alkyl groups and one cycloalkyl group.

[0479] As used herein, the term “amine” describes both a -NR’R” group and a -NR'- group, wherein R’ and R" are each independently hydrogen, alkyl, cycloalkyl, aryl, as these terms are defined hereinbelow.

[0480] The amine group can therefore be a primary amine, where both R’ and R” are hydrogen, a secondary amine, where R’ is hydrogen and R” is alkyl, cycloalkyl or aryl, or a tertiary amine, where each of R’ and R” is independently alkyl, cycloalkyl or aryl.

[0481] Alternatively, R' and R" can each independently be hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano, nitro, azo, sulfonamide, carbonyl, C-carboxylate, O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea, N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine. The term “amine” is used herein to describe a -NR'R" group in cases where the amine is an end group, as defined hereinunder, and is used herein to describe a -NR'- group in cases where the amine is a linking group or is or part of a linking moiety.

[0482] The term "alkyl" describes a saturated aliphatic hydrocarbon including straight chain and branched chain groups. Preferably, the alkyl group has 1 to 30, or 1 to 20 carbon atoms. Whenever a numerical range; e.g., "1-20", is stated herein, it implies that the group, in this case the alkyl group, may contain 1 carbon atom, 2 carbon atoms, 3 carbon atoms, etc., up to and including 20 carbon atoms. The alkyl group may be substituted or unsubstituted. Substituted alkyl may have one or more substituents, whereby each substituent group can independently be, for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate, O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea, N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine.

[0483] The alkyl group can be an end group, as this phrase is defined hereinabove, wherein it is attached to a single adjacent atom, or a linking group, as this phrase is defined hereinabove, which connects two or more moieties via at least two carbons in its chain. When the alkyl is a linking group, it is also referred to herein as “alkylene” or “alkylene chain”.

[0484] Alkene and Alkyne, as used herein, are an alkyl, as defined herein, which contains one or more double bond or triple bond, respectively.

[0485] The term "cycloalkyl" describes an all-carbon monocyclic ring or fused rings (z.e., rings which share an adjacent pair of carbon atoms) group where one or more of the rings does not have a completely conjugated pi-electron system. Examples include, without limitation, cyclohexane, adamantine, norbomyl, isobomyl, and the like. The cycloalkyl group may be substituted or unsubstituted. Substituted cycloalkyl may have one or more substituents, whereby each substituent group can independently be, for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate, O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea, N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine. The cycloalkyl group can be an end group, as this phrase is defined hereinabove, wherein it is attached to a single adjacent atom, or a linking group, as this phrase is defined hereinabove, connecting two or more moieties at two or more positions thereof. The term "heteroalicyclic" describes a monocyclic or fused ring group having in the ring(s) one or more atoms such as nitrogen, oxygen and sulfur. The rings may also have one or more double bonds. However, the rings do not have a completely conjugated pi-electron system. Representative examples are piperidine, piperazine, tetrahydrofurane, tetrahydropyrane, morpholino, oxalidine, and the like.

[0486] The heteroalicyclic may be substituted or unsubstituted. Substituted heteroalicyclic may have one or more substituents, whereby each substituent group can independently be, for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate, O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea, O-carbamate, N-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine. The heteroalicyclic group can be an end group, as this phrase is defined hereinabove, where it is attached to a single adjacent atom, or a linking group, as this phrase is defined hereinabove, connecting two or more moieties at two or more positions thereof.

[0487] The term "aryl" describes an all-carbon monocyclic or fused-ring polycyclic (z.e., rings which share adjacent pairs of carbon atoms) groups having a completely conjugated pi-electron system. The aryl group may be substituted or unsubstituted. Substituted aryl may have one or more substituents, whereby each substituent group can independently be, for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate, O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea, N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine. The aryl group can be an end group, as this term is defined hereinabove, wherein it is attached to a single adjacent atom, or a linking group, as this term is defined hereinabove, connecting two or more moieties at two or more positions thereof.

[0488] The term "heteroaryl" describes a monocyclic or fused ring (z.e., rings which share an adjacent pair of atoms) group having in the ring(s) one or more atoms, such as, for example, nitrogen, oxygen and sulfur and, in addition, having a completely conjugated pi-electron system. Examples, without limitation, of heteroaryl groups include pyrrole, furan, thiophene, imidazole, oxazole, thiazole, pyrazole, pyridine, pyrimidine, quinoline, isoquinoline and purine. The heteroaryl group may be substituted or unsubstituted. Substituted heteroaryl may have one or more substituents, whereby each substituent group can independently be, for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate, O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea, O-carbamate, N-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine. The heteroaryl group can be an end group, as this phrase is defined hereinabove, where it is attached to a single adjacent atom, or a linking group, as this phrase is defined hereinabove, connecting two or more moieties at two or more positions thereof. Representative examples are pyridine, pyrrole, oxazole, indole, purine and the like.

[0489] The term "halide" and “halo” describes fluorine, chlorine, bromine or iodine.

[0490] The term “haloalkyl” describes an alkyl group as defined above, further substituted by one or more halide.

[0491] The term “sulfate” describes a -O-S(=O)2-OR’ end group, as this term is defined hereinabove, or an -O-S(=O)2-O- linking group, as these phrases are defined hereinabove, where R’ is as defined hereinabove.

[0492] The term “thiosulfate” describes a -O-S(=S)(=O)-OR’ end group or a -O-S(=S)(=O)-O-linking group, as these phrases are defined hereinabove, where R’ is as defined hereinabove.

[0493] The term “sulfite” describes an -O-S(=O)-O-R’ end group or a -O-S(=O)-O- group linking group, as these phrases are defined hereinabove, where R’ is as defined hereinabove.

[0494] The term “thiosulfite” describes a -O-S(=S)-O-R’ end group or an -O-S(=S)-O- group linking group, as these phrases are defined hereinabove, where R’ is as defined hereinabove.

[0495] The term “sulfinate” describes a -S(=O)-OR’ end group or an -S(=O)-O- group linking group, as these phrases are defined hereinabove, where R’ is as defined hereinabove.

[0496] The term “sulfoxide” or “sulfinyl” describes a -S(=O)R’ end group or an -S(=O)- linking group, as these phrases are defined hereinabove, where R’ is as defined hereinabove.

[0497] The term "sulfonate” describes a -S(=O)2-R’ end group or an -S(=O)2- linking group, as these phrases are defined hereinabove, where R’ is as defined herein.

[0498] The term “S-sulfonamide” describes a -S(=O)2-NR’R” end group or a -S(=O)2-NR’-linking group, as these phrases are defined hereinabove, with R’ and R” as defined herein.

[0499] The term "N- sulfonamide" describes an R’S(=O)2-NR”- end group or a -S(=O)2-NR’-linking group, as these phrases are defined hereinabove, where R’ and R’ ’ are as defined herein.

[0500] The term "carbonyl" or "carbonate" as used herein, describes a -C(=O)-R’ end group or a -C(=O)- linking group, as these phrases are defined hereinabove, with R’ as defined herein. The term "thiocarbonyl" as used herein, describes a -C(=S)-R’ end group or a -C(=S)-linking group, as these phrases are defined hereinabove, with R’ as defined herein.

[0501] The term “hydroxyl” describes a -OH group. The term "alkoxy" describes both an -O-alkyl and an -O-cycloalkyl group, as defined herein. The term alkoxide describes -R’O“ group, with R’ as defined herein.

[0502] The term "aryloxy" describes both an -O-aryl and an -O-heteroaryl group, as defined herein.

[0503] The term "thiohydroxy" or “thiol” describes a -SH group. The term “thiolate” describes a -S’ group.

[0504] The term "thioalkoxy" describes both a -S-alkyl group, and a -S-cycloalkyl group, as defined herein.

[0505] The term "thioaryloxy" describes both a -S-aryl and a -S-heteroaryl group, as defined herein.

[0506] The “hydroxyalkyl” is also referred to herein as “alcohol”, and describes an alkyl, as defined herein, substituted by a hydroxy group.

[0507] The term "cyano" describes a -C=N group.

[0508] The term “isocyanate” describes an -N=C=O group.

[0509] The term “isothiocyanate” describes an -N=C=S group.

[0510] The term "nitro" describes an -NO2 group.

[0511] The term “acyl halide” describes a -(C=O)R"" group wherein R"" is halide, as defined hereinabove.

[0512] The term “carboxylate” as used herein encompasses C-carboxylate and O-carboxylate. The term “C-carboxylate” describes a -C(=O)-OR’ end group or a -C(=O)-O- linking group, as these phrases are defined hereinabove, where R’ is as defined herein.

[0513] The term “O-carboxylate” describes a -OC(=O)R’ end group or a -OC(=O)- linking group, as these phrases are defined hereinabove, where R’ is as defined herein.

[0514] A carboxylate can be linear or cyclic. When cyclic, R’ and the carbon atom are linked together to form a ring, in C-carboxylate, and this group is also referred to as lactone. Alternatively, R’ and O are linked together to form a ring in O-carboxylate. Cyclic carboxylates can function as a linking group, for example, when an atom in the formed ring is linked to another group.

[0515] The term “thiocarboxylate” as used herein encompasses C-thiocarboxylate and O-thiocarboxylate.

[0516] The term “C-thiocarboxylate” describes a -C(=S)-OR’ end group or a -C(=S)-O- linking group, as these phrases are defined hereinabove, where R’ is as defined herein.

[0517] The term “O-thiocarboxylate” describes a -OC(=S)R’ end group or a -OC(=S)- linking group, as these phrases are defined hereinabove, where R’ is as defined herein. A thiocarboxylate can be linear or cyclic. When cyclic, R’ and the carbon atom are linked together to form a ring, in C-thiocarboxylate, and this group is also referred to as thiolactone. Alternatively, R’ and O are linked together to form a ring in O-thiocarboxylate. Cyclic thiocarboxylates can function as a linking group, for example, when an atom in the formed ring is linked to another group.

[0518] The term “carbamate” as used herein encompasses N-carbamate and O-carbamate.

[0519] The term “N-carbamate” describes an R”OC(=O)-NR’- end group or a -OC(=O)-NR’-linking group, as these phrases are defined hereinabove, with R’ and R” as defined herein.

[0520] The term “O-carbamate” describes an -OC(=O)-NR’R” end group or an -OC(=O)-NR’- linking group, as these phrases are defined hereinabove, with R’ and R” as defined herein.

[0521] A carbamate can be linear or cyclic. When cyclic, R’ and the carbon atom are linked together to form a ring, in O-carbamate. Alternatively, R’ and O are linked together to form a ring in N-carbamate. Cyclic carbamates can function as a linking group, for example, when an atom in the formed ring is linked to another group.

[0522] The term “carbamate” as used herein encompasses N-carbamate and O-carbamate..

[0523] The term “thiocarbamate” as used herein encompasses N-thiocarbamate and O-thiocarbamate.

[0524] The term “O-thiocarbamate” describes a -OC(=S)-NR’R” end group or a -OC(=S)-NR’- linking group, as these phrases are defined hereinabove, with R’ and R” as defined herein.

[0525] The term “N-thiocarbamate” describes an R”OC(=S)NR’- end group or a -OC(=S)NR’-linking group, as these phrases are defined hereinabove, with R’ and R” as defined herein.

[0526] Thiocarbamates can be linear or cyclic, as described herein for carbamates.

[0527] The term “dithiocarbamate” as used herein encompasses S -dithiocarbamate and N-dithiocarbamate.

[0528] The term “S -dithiocarbamate” describes a -SC(=S)-NR’R” end group or a -SC(=S)NR’- linking group, as these phrases are defined hereinabove, with R’ and R” as defined herein.

[0529] The term “N-dithiocarbamate” describes an R”SC(=S)NR’- end group or a -SC(=S)NR’-linking group, as these phrases are defined hereinabove, with R’ and R” as defined herein.

[0530] The term "urea", which is also referred to herein as “ureido”, describes a -NR’C(=O)-NR”R’ ’ ’ end group or a -NR’C(=O)-NR”- linking group, as these phrases are defined hereinabove, where R’ and R” are as defined herein and R'" is as defined herein for R' and R". The term “thiourea”, which is also referred to herein as “thioureido”, describes a -NR’-C(=S)-NR”R”’ end group or a -NR’-C(=S)-NR”- linking group, with R’, R” and R’” as defined herein.

[0531] The term “amide” as used herein encompasses C-amide and N-amide.

[0532] The term “C-amide” describes a -C(=O)-NR’R” end group or a -C(=O)-NR’- linking group, as these phrases are defined hereinabove, where R’ and R” are as defined herein.

[0533] The term “N-amide” describes a R’C(=O)-NR”- end group or a R’C(=O)-N- linking group, as these phrases are defined hereinabove, where R’ and R” are as defined herein.

[0534] An amide can be linear or cyclic. When cyclic, R’ and the carbon atom are linked together to form a ring, in C-amide, and this group is also referred to as lactam. Cyclic amides can function as a linking group, for example, when an atom in the formed ring is linked to another group.

[0535] As used herein, the term “alkylene glycol” describes a -O-[(CR’R”)Z-O]y-R”’ end group or a -O-[(CR’R”)Z-O]y- linking group, with R’, R” and R’” being as defined herein, and with z being an integer of from 1 to 10, preferably, from 2 to 6, more preferably 2 or 3, and y being an integer of 1 or more. Preferably R’ and R” are both hydrogen. When z is 2 and y is 1, this group is ethylene glycol. When z is 3 and y is 1, this group is propylene glycol. When y is 2-4, the alkylene glycol is referred to herein as oligo(alkylene glycol). When y is greater than 4, for example, is greater than 6, or than 10, or than 20, the alkylene glycol is referred to herein as poly (alkylene glycol).

[0536] Herein, an “ethoxylated” material describes an acrylic or methacrylic compound which comprises one or more alkylene glycol groups, or, preferably, one or more alkylene glycol chains, as defined herein. Ethoxylated (meth)acrylate materials can be mono-functional, or, preferably, multi-functional, namely, di-functional, tri-functional, tetrafunctional, etc.

[0537] In multi-functional materials, typically, each of the (meth)acrylate groups are linked to an alkylene glycol group or chain, and the alkylene glycol groups or chains are linked to one another through a branching unit, such as, for example, a branched alkyl, cycloalkyl, aryl (e.g., Bisphenol A), etc.

[0538] In some embodiments, the ethoxylated material comprises at least one, or at least two ethoxylated group(s), that is, at least one or at least two alkylene glycol moieties or groups. Some or all of the alkylene glycol groups can be linked to one another to form an alkylene glycol chain. For example, an ethoxylated material that comprises 30 ethoxylated groups can comprise a chain of 30 alkylene glycol groups linked to one another, two chains, each, for example, of 15 alkylene glycol moieties linked to one another, the two chains linked to one another via a branching moiety, or three chains, each, for example, of 10 alkylene glycol groups linked to one another, the three chains linked to one another via a branching moiety. Shorter and longer chains are also contemplated.

[0539] The ethoxylated material can comprise one, two or more alkylene glycol chains, of any length.

[0540] The term “branching unit” as used herein describes a multi-radical, preferably aliphatic or alicyclic group. By “multi-radical” it is meant that the unit has two or more attachment points such that it links between two or more atoms and / or groups or moieties.

[0541] In some embodiments, the branching unit is derived from a chemical moiety that has two, three or more functional groups. In some embodiments, the branching unit is a branched alkyl or a cycloalkyl (alicyclic) or an aryl (e.g., phenyl) as defined herein.

[0542] As used herein, HDT refers to a temperature at which the respective formulation or combination of formulations deforms under a predetermined load at some certain temperature. Suitable test procedures for determining the HDT of a formulation or combination of formulations are the ASTM D-648 series, particularly the ASTM D-648-06 and ASTM D-648-07 methods. In various exemplary embodiments of the invention the core and shell of the structure differ in their HDT as measured by the ASTM D-648-06 method as well as their HDT as measured by the ASTM D-648-07 method. In some embodiments of the present invention the core and shell of the structure differ in their HDT as measured by any method of the ASTM D-648 series. In the majority of the examples herein, HDT at a pressure of 0.45 MPa was used.

[0543] Herein, "Tg" of a material refers to glass transition temperature defined as the location of the local maximum of the E" curve, where E" is the loss modulus of the material as a function of the temperature.

[0544] Broadly speaking, as the temperature is raised within a range of temperatures containing the Tg temperature, the state of a material, particularly a polymeric material, gradually changes from a glassy state into a rubbery state.

[0545] Herein, "Tg range" is a temperature range at which the E" value is at least half its value (e.g., can be up to its value) at the Tg temperature as defined above.

[0546] Without wishing to be bound to any particular theory, it is assumed that the state of a polymeric material gradually changes from the glassy state into the rubbery within the Tg range as defined above. The lowest temperature of the Tg range is referred to herein as Tg(low) and the highest temperature of the Tg range is referred to herein as Tg(high).

[0547] Herein throughout, whenever a curable material is defined by a property of a hardened material obtained therefrom, it is to be understood that this property is for a hardened material obtained from this curable material per se. By “Tensile strength” it is meant the maximum stress that a material can withstand while being stretched or pulled before breaking. Tensile strength may be determined, for example, according to ASTM D-638-03.

[0548] By “Tensile modulus” it is meant the stiffness of a material, defined as the relationship between stress (force per unit area) and strain (proportional deformation) in a material in the linear elasticity regime of a uniaxial deformation. Tensile modulus may be determined, for example, according to ASTM D-638-04.

[0549] By “flexural strength” or “flexural stress” it is meant the stress in a material just before it yields in a flexure test. Flexural strength may be determined, for example, according to ASTM D-790-03, unless otherwise indicated.

[0550] By “flexural modulus” or “flexural Y modulus” it is meant the ratio of stress to strain in flexural deformation, which is determined from the slope of a stress-strain curve produced by a flexural test such as the ASTM D790. Flexural modulus may be determined, for example, according to ASTM D-790-04, unless otherwise indicated.

[0551] Herein throughout, unless otherwise indicated, viscosity values are provided for a viscosity of a material or a formulation when measured at 25 °C on a Brookfield’s viscometer. Measured values are provided in centipoise units, which correspond to mPa / second units.

[0552] By “transparent curable formulation” it is meant a curable formulation, as defined herein, which provides, when hardened, a transparent material. Such a formulation is also referred to herein as “clear” formulation, and encompasses formulations that are devoid of pigments, as described herein.

[0553] The term “transparent” describes a property of a hardened material that reflects the transmittance of light therethrough. A transparent material is typically characterized as capable of transmitting at least 70 % of a light that passes therethrough, or by transmittance of at least 70 %. Transmittance of a material can be determined using methods well known in the art.

[0554] A transparent curable formulation as described herein can be transparent also before it is hardened.

[0555] A transparent curable formulation as described herein can be characterized as colorless and / or by color properties as determined by the L*a*b* scale, as described hereinafter for a hardened material.

[0556] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0557] Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.

[0558] EXAMPLES

[0559] Reference is now made to the following examples, which together with the above descriptions illustrate some embodiments of the invention in a non-limiting fashion.

[0560] EXAMPLE 1

[0561] Design

[0562] The present inventors have sought after curable formulations which are usable for additive manufacturing, particularly, 3D inkjet printing, and which provide hardened materials that feature improved toughness, particularly compared to commonly practiced formulations usable in 3D inkjet printing.

[0563] More specifically, the present inventors have searched for curable formulations that provide, when hardened, materials that feature Izod XY notched impact resistance, as defined herein, which is higher than 40, or higher than 50, preferably higher than 60, or even higher than 80 J / m.

[0564] As used herein, the phrase “impact resistance”, which is also referred to interchangeably, herein and in the art, as “impact strength” or simply as “impact”, describes the resistance of a material to fracture by a mechanical impact, and is expressed in terms of the amount of energy absorbed by the material before complete fracture. Impact resistance can be measured using, for example, the ASTM D256-06 standard Izod impact testing (also known as “Izod notched impact”, or as “Izod impact resistance”), and / or as described hereinunder, and is expressed as J / m.

[0565] As used herein, the term "Izod impact resistance" refers to the loss of energy per unit of thickness following an impact force applied to the respective hardened material. Suitable test procedures for determining the Izod impact resistance of a hardened material are the ASTM D-256 series, particularly the ASTM D-256-06 series.

[0566] In most of the standard ASTM methods there is need to machinate a notch. According to such procedures, the Izod impact resistance measures the ability of the hardened material to absorb impact energy along the XY plane when a notch is cut into the sample. The cut notch introduces a localized stress concentration, simulating real-world imperfections, and helps evaluate how the material will fail under sudden stress in the layer plane. The Izod impact resistance measured in such procedures is also referred to herein and in the art as “Izod XY cut-notched” or “Izod XY notched” or simply as “Izod XY” or “Izod cut-notched”.

[0567] However, in alternative procedures, the Izod impact resistance is measured without introducing a notch, along the ZX plane, and determines the material’s impact resistance across the layer boundaries, and the overall integrity of the vertical structure. The Izod impact resistance measured in such procedures is also referred to herein and in the art as “Izod ZX unnotched” or simply as “Izod unnotched” or “Izod ZX”.

[0568] Generally, Izod XY notched impact resistance is measured for objects printed in a glossy mode, and Izod ZX impact resistance is measured for objects printed in a matte mode.

[0569] It is to be noted that Izod XY notched impact resistance is more indicative of the actual toughness of a hardened material.

[0570] Herein, Izod XY notched impact resistance values are reported for objects printed in matte mode, unless otherwise indicated.

[0571] Izod XY notched impact resistance measurements were performed using Zwick / Roell HIT 5.5P as a pendulum impact tester, using Zwick / Roell notching machine for notch cutting, and 1 Joule hammer, according to ASTM D256.

[0572] Herein, objects printed in matte mode refer to objects printed using a support material formulation, whereby removal of the hardened support material reveals a hardened mixed layer, comprising a hardened mixture of support material and modeling material formulation, which often has a relatively non-reflective appearance, and hence is referred to herein as “matte”.

[0573] Objects that lack such a hardened mixture (e.g., wherein support material formulation was not applied thereon) are also described herein as “glossy” in comparison.

[0574] The present inventors have performed the 3D inkjet printing using a system as described in FIG. 1A, which employs a Mercury lamp as a radiation curing energy source and can perform a PolyJet printing process, unless otherwise indicated. When indicated, a system as described in FIGs. 1B-D, which employs a LED radiation source, was used. The present inventors have conceived utilizing a material of the a-(unsaturated alkoxyalkyljacrylate family as described herein.

[0575] The present inventors have performed laborious studies in order to arrive at curable formulations that indeed provide the desired toughness in terms of Izod impact resistance as described herein, while at the same time meeting the process requirements in terms of, for example, viscosity and jettability, and while providing other desirable properties such as HDT, flexural strength, flexural modulus, and elongation at break, as these are defined herein.

[0576] Following these laborious studies, the present inventors have designed and successfully prepared and practiced modeling material formulations that meet the 3D-printing process requirements, and provide hardened materials that feature the desired properties.

[0577] Table 1 below presents exemplary curable materials and other components that were considered to be included in the modeling material formulations.

[0578] Table 1

[0579] >

[0580]

[0581]

[0582] (Table 1; Cont.)

[0583] * Curable Black paste is a dispersion of a black pigment (e.g., Carbon black) in a mixture of mono-functional and multi-functional acrylic materials

[0584] ** Curable White paste is a dispersion of TiO2 particles in a mixture of mono-functional and multi-functional acrylic materials The present inventors have tested various formulations made of various combinations of these components, at varying concentrations (presented in % by weight of the total weight of the formulation), prepared by mixing all the materials, optionally while heating, and have tested the performance of these formulations in terms of meeting the process requirements (e.g., viscosity, jettability and surface tension), and, importantly, in terms of the properties of the hardened material, particularly the Izod impact resistance.

[0585] Formulations featuring viscosity at 70 °C of up to 50 cps, preferably of 15-20 cps; surface tension of 30-35 dyne / cm, were considered as meeting the process requirement. Formulations considered as jettable are those that allow smooth inkjet printing in terms of, for example, uniform droplets and no clogging of nozzles throughout the process.

[0586] Formulations that provide the following properties of the hardened material were determined as meeting the study’s goal:

[0587] HDT (ASTM D648) higher than 50 °C (e.g., 50-60 °C);

[0588] Tensile Strength (ASTM D638) 30-50 MPa;

[0589] Elongation at break (ASTM D638) 25-40 %;

[0590] Flexural Strength (ASTM D790) 40-60 MPa;

[0591] Flexural Modulus (ASTM D790) 1300-1800 MPa;

[0592] Izod Notched XY impact resistance higher than 40, preferably higher than 60 (e.g., 60- 100) J / m;

[0593] Izod Un-notched ZX impact resistance higher than 100, preferably higher than 120 (e.g., 120-220) J / m;

[0594] Creep (at 70 % humidity and 40 °C) similar or lower than a commercially available formulation (e.g., such as marketed under the tradename Vero®);

[0595] Water absorption lower than 3 %; preferably lower (e.g., 1-1.5 %), as measured for a 60x60x1 mm cube according to ASTM D570;

[0596] Mechanical specimens according to ASTM D638, D790, D256 were printed using the tested formulations on a system such as described in FIGs. 1A-C, equipped with a Mercury lamp as the radiation curing source (J750 / J850 printer from Stratasys Ltd., IL). Some specimens were printed using the tested formulations on a system such as described in FIGs. 1B-C, equipped with a LED as the radiation curing source (J3 / 5 printer from Stratasys Ltd., IL).

[0597] Unless otherwise indicated, data below is presented for 3D-printed mechanical specimen printed using a system as shown in FIG. 1A equipped with a Mercury lamp as a radiation source as described herein. Data for 3D-printed mechanical specimen printed using a system as shown in FIGs. 1B-D equipped with a LED radiation source are marked as (L).

[0598] Unless otherwise indicated, data is provided for printed objects following a further treatment for 12 hours at 45 °C in a CureBox chamber equipped with LED irradiation at 450 nm. Data provided for printed objects that were not subjected to a further treatment is marked by *.

[0599] As a support material formulation, formulations marketed under the tradename SUP705b and SUP706b were used.

[0600] As Reference formulations, a transparent commercially available formulation marketed under the tradename Vero®Clear, denoted as “Ref. CL”, a commercially available white formulation marketed under the tradename Vero®Pure White denoted as “Ref. W”, or a commercially available black formulation marketed under the tradename Vero®BlackPlus denoted as “Ref. B”, were used for comparison.

[0601] The following examples describe the studies conducted while devising transparent and opaque colored formulations.

[0602] EXAMPLE 2

[0603] Transparent Formulations

[0604] Table 2 below presents exemplary tested formulations that were prepared as described above for providing transparent clear (colorless) hardened materials. Transparent colored formulations are similarly prepared by adding a transparent dye or pigment to the formulation, typically at a concentration of about 10’5- 10’3.

[0605] Transparency was measured either visually, or by color properties as determined by the L*a*b* scale, as described herein.

[0606] Table 2

[0607]

[0608]

[0609] All of these exemplary formulations feature desirable viscosity values. Formulation I features the desirable surface tension, whereby all the other formulations feature slightly lower than desirable surface tension (e.g., 25-28). Formulations I- VII were jettable while Formulations VIII and IX were not jettable on the tested printers.

[0610] Table 3 below presents the mechanical and physical properties of the 3D-object obtained from each of these exemplary formulations, compared to a commercially available transparent formulation. Table 3

[0611]

[0612] The following can be deduced from the data obtained:

[0613] Combining Components Al and A2 at a ratio lower than 2: 1 results in phase separation and hence in opaque hardened material (see, for example, Formulations VI and VII compared to Formulations VIII and IX);

[0614] Component C, in an amount higher than 25 % by weight, adversely affects the properties, particularly jettability and the impact resistance (toughness) of the hardened material (see, for example, Formulations VII and IX);

[0615] Inclusion of Component C and of Component D in an amount higher than 10 % by weight is required to obtain the desired impact resistance (toughness) of the hardened material (see, for example, Formulation VI versus all other formulations);

[0616] Inclusion of Component El in an amount higher than 5 % by weight adversely affects jettability (see, for example, Formulation I compared to Formulation IX);

[0617] Inclusion of Component E2 provides improved properties compared to Component E3 (see, for example, Formulation I compared to Formulation V).

[0618] Overall, these studies indicated that formulations that comprise a combination of Component C, in an amount of from 15 to 25, preferably from about 20 to about 23, % by weight, Component Al, Component D in an amount of from 15 to 25 % by weight, and Component El (in an amount lower than 5 % by weight) and / or E2 (in an amount of from 5 to 10 % by weight), provide desirable performance.

[0619] EXAMPLE 3

[0620] Opaque White Formulations

[0621] Table 4 below presents the exemplary tested formulations that were prepared as described above for providing opaque white hardened materials.

[0622] Table 4

[0623]

[0624] All of these exemplary formulations meet the process requirements with regard to viscosity, surface tension and jettability.

[0625] In Formulation II, phase separation was observed.

[0626] Table 5 below presents the mechanical and physical properties of the 3D-object obtained from each of these exemplary formulations, following further treatment for 12 hours at 45 °C in a CureBox chamber equipped with LED irradiation at 450 nm, and compared to a corresponding reference formulation (Ref. W as described herein). Table 5

[0627]

[0628] The following can be deduced from the obtained data:

[0629] Combining Component Al with a hydrophobic component such as A2 and / or with Component B2 is required for providing an opaque material;

[0630] Inclusion of Component C, in an amount lower than 15 % by weight adversely affects the impact resistance (toughness) of the hardened material (see, for example, Formulation XII versus Formulations XI, XIII and XIV);

[0631] Inclusion of Component El is preferred over Component G (see, for example, Formulation XIII versus I), presumably, and without being bound by any particular theory, due to the presence and / or nature of the poly(propylene glycol) moieties that are present in Component El.

[0632] Combining Component C in an amount higher than 15 % (e.g., 15-25 or 20-25, or about 20, % by weight), with Component D (10-15 % by weight) and Component El (8-12 % by weight) provide the best performance, particularly in terms of the Izod XY notched impact resistance (toughness) of the hardened material (see, for example, Formulations XIII and XIV). EXAMPLE 4

[0633] Opaque Black Formulations

[0634] Table 6 below presents exemplary tested formulations that were prepared as described above for providing opaque black hardened materials as exemplary formulations for providing opaque colored hardened materials which comprise an opaque pigment.

[0635] Table 6

[0636]

[0637] Table 7 below presents the mechanical and physical properties of the 3D-object obtained from each of these exemplary formulations, compared to a respective commercially available formulation. Table 7

[0638]

[0639] The following can be deduced from the obtained data:

[0640] First, it can be seen that Formulations containing Component C in an amount lower than 20 % by weight provide poor mechanical performance of objects obtained thereby, particularly low Izod XY impact resistance, and low elongation at break (compare, for example, Formulations XXIV and XXV to all other formulations.

[0641] While Formulation XXI provided objects exhibiting the best performance, the water absorption of this formulation was relatively high (> 3 %), and hence formulations that provide reduced water absorption were sought for, as exemplified for Formulations XXII-XXV. To this end, the amount of Component Al was reduced and Component A2 was added, while, as Component B, the more hydrophobic Component B2 was selected. It can be seen that a total amount of Components Al, A2 and B2 should be at least 35 % by weight, whereby the total amount of Component A2 should preferably not exceed 10 % by weight. Compare, for example, Formulations XXII and XXIII to Formulations XXIV and XXV.

[0642] Further, it can be seen that an amount of Component E of about 10 % by weight is preferred (compared to less than 10 %), and that Component El may be preferred for reducing water absorption. Further, comparing the mechanical and physical properties of the 3D-object obtained from exemplary formulation XXVI versus exemplary Formulation I shown in Tables 1 and 2 above indicate that adding a black pigment to a transparent formulation maintains the mechanical properties of the printed object, without requiring major adjustment of the formulation’s components.

[0643] EXAMPLE 5

[0644] Intermediate Concluding Insights

[0645] Based on the studies conducted, it can be seen that formulations that provide a successful performance both in terms of meeting process requirements and of providing a hardened material with a desirable toughness and other mechanical and physical properties, the curable formulation should comprise at least Component Al, Component C, Component D and Component El and / or E2. The amount of Component C should be about 15-25, preferably about 20 % by weight. The amount of the other components, and the addition of further components (e.g., Component B and / or F), can be manipulated so as to provide properties such as opacity or transparency, hydrophobicity (reduced water absorption), improved jettability, etc.

[0646] Generally, a total amount of Component A (e.g., Component Al alone or combined with Component A2) ranges from 20 to 30 % by weight, and can be, for example, around 25 % by weight.

[0647] A ratio between Components Al and Components A2 and El may determine the transparency / opacity of the formulation, with a ratio lower than 2:1 typically results in opaque formulations.

[0648] Apart from Component A, additional mono-functional materials (Component B) can be added to the formulation, so as to manipulate hydrophobicity, toughness, reactivity, hardness, and / or flexibility.

[0649] Generally, a total amount of mono-functional curable materials when both Component A and Component B are included, ranges from 20 to 45, or from 25 to 45, % by weight.

[0650] The total amount of Component E is typically in a range of from 5 to 15, or from 8 to 12, % by weight. Components El and E2, or a combination thereof is preferred.

[0651] Apart from Components D and E, additional multi-functional, preferably di-functional, materials, Component F, can be added to the formulation, so as to manipulate properties such as hydrophobicity, toughness, reactivity, hardness, and / or flexibility. Typically, one or more of Components Fl, F2, F3 and F4 can be added, in an amount of from 10-20 % by weight, although higher amounts are also contemplated. In colored formulations, Components B 1 and Fl are typically added, to improve properties, each typically in an amount of from 10-20 % by weight, although higher amounts are also contemplated.

[0652] FIG. 4 presents photographs of exemplary white and black objects, obtained from exemplary opaque formulations as described herein.

[0653] The present inventors have further uncovered that for some of the tested formulations, a further treatment is desirable, as it further improves the mechanical properties of the printed object. An exemplary such treatment comprises photobleaching, which is effected by exposing the printed object to heat and irradiation. Preferably, objects are placed in an oven, at a temperature lower than the HDT of the hardened material, typically 45 °C, equipped with operated LED radiation source (450 nm), for 10-24 hours.

[0654] FIG. 5 presents the effect of various further treatment protocols after printing on the properties of a final object made of an exemplary transparent clear formulation as described herein (see, Example 2). Standard PT represents photobleaching by application of heat and UV LED irradiation as described herein. Thermal PT represents heating in an open at 45 °C for 12 hours, without irradiation.

[0655] For the Matt (i.e. matte) mode measurements, water jet (WJ) was applied to remove the hardened support material either before or after the indicated PT.

[0656] As can be seen in FIG. 5, upper panel, objects printed in glossy mode exhibited improved performance after both further treatment protocols (thermal and standard). As can be seen in FIG.

[0657] 5, lower panel, objects subjected to photobleaching after support removal exhibited less pronounced deformation when placed in a humidity chamber (40 °C and 70 % humidity), compared to objects not subjected to a further treatment, or objects subjected to a further treatment before support removal.

[0658] Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

[0659] It is the intent of the applicant(s) that all publications, patents and patent applications referred to in this specification are to be incorporated in their entirety by reference into the specification, as if each individual publication, patent or patent application was specifically and individually noted when referenced that it is to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is / are hereby incorporated herein by reference in its / their entirety.

Claims

WHAT IS CLAIMED IS:

1. A modeling material formulation usable for additive manufacturing of a three-dimensional object, the modeling material formulation comprising:at least one mono-functional (meth) acrylate featuring, when hardened, Tg higher than 80, or higher than 100 °C (Component A);at least one multi-functional urethane (meth) acrylate featuring, when hardened, Tg higher than 80, or higher than 100 °C (Component D);at least one multi-functional polyether (meth) acrylate material featuring, when hardened, Tg lower than 20, or lower than 0, °C, optionally featuring MW higher than 500 grams / mol (Component E); andat least one acrylate material represented by Formula I (Component C):Formula Iwherein:Ri and R2 are each independently hydrogen or alkyl;Y is selected from O, S, NR3, and CR4R5, wherein R3, R4 and R5 are each independently selected from hydrogen and alkyl; andXi and X2 are each independently a substituted or unsubstituted alkylene of 1-4 carbon atoms in length, such that the total number of atoms of a backbone chain formed of Xi, Y and X2 is no more than 6.

2. The modeling material formulation of claim 1, wherein Y is O, the compound being an a-(unsaturated alkoxyalkyl) acrylate.

3. The modeling material formulation of claim 1 or 2, wherein the total number of carbon atoms in Xi and X2 is no more than 5.

4. The modeling material formulation of claim 3, wherein Xi and X2 are each methylene.

5. The modeling material formulation of any one of claims 1 to 4, wherein Ri is alkyl and / or R2 is hydrogen.

6. The modeling material formulation of any one of claims 1 to 5, wherein Component C is or comprises methyl 2-((allyloxy)methyl)acrylate.

7. The modeling material formulation of any one of claims 1 to 6, wherein an amount of said Component C ranges from 15 to 25, preferably from 18 to 22, or is about 20, % by weight, of the total weight of the formulation.

8. The modeling material formulation of any one of claims 1 to 7, wherein said Component D is or comprises a multi-functional aliphatic urethane (meth)acrylate featuring, when hardened, said Tg.

9. The modeling material formulation of any one of claims 1 to 8, wherein said Component D is or comprises a multi-functional aliphatic urethane (meth)acrylate featuring, when hardened said Tg.

10. The modeling material formulation of any one of claims 1 to 9, wherein said Component D is or comprises a di-functional aliphatic urethane methacrylate featuring, when hardened said Tg.

11. The modeling material formulation of any one of claims 1 to 10, wherein an amount of said Component D is at least 10 % by weight, or ranges from 10 to 20, or from 10 to 15, % by weight, of the total weight of the formulation.

12. The modeling material formulation of any one of claims 1 to 11, wherein said Component E comprises a di-functional polyether (meth)acrylate.

13. The modeling material formulation of any one of claims 1 to 12, wherein said Component E is or comprises a multi-functional aliphatic (meth)acrylate featuring a poly(alkylene glycol moiety) (Component E2).

14. The modeling material formulation of any one of claims 1 to 13, wherein said Component E is or comprises a di-functional aliphatic acrylate featuring a poly(alkylene glycol moiety) .

15. The modeling material formulation of claim 14, wherein said Component E has a molecular weight in a range of from 500 to 2000, or from 500 to 1000, grams / mol.

16. The modeling material formulation of any one of claims 1 to 12, wherein said Component E is or comprises a multi-functional polyether urethane (meth)acrylate (Component El).

17. The modeling material formulation of claim 16, wherein said Component El is a multi-functional polyether urethane (meth)acrylate featuring MW higher than 2,000 or higher than 3,000 grams / mol, or higher (Component El).

18. The modeling material formulation of claim 16 or 17, wherein said Component El is a di-functional polyether urethane acrylate.

19. The modeling material formulation of any one of claims 1 to 12 and 16 to 18, wherein said Component E is or comprises Component El, which is a di-functional urethane acrylate featuring a poly(alkylene glycol) moiety and having MW of at least 2,000, or at least 3,000 or at least 4,000 or at least 5,000 grams / mol.

20. The modeling material formulation of claim 19, wherein said poly(alkylene glycol) moiety is or comprises poly(isopropylene glycol).

21. The modeling material formulation of any one of claims 1 to 12, wherein said Component E is or comprises a multi-functional ethoxylated aromatic (meth)acrylate featuring at least 10 ethoxylated groups (Component E3).

22. The modeling material formulation of any one of claims 1 to 12, wherein said Component E comprises at least one of a multi-functional aliphatic (meth) acrylate featuring a poly(alkylene glycol moiety) (Component E2) and a multi-functional polyether urethane (meth)acrylate featuring MW higher than 2,000 or higher than 3,000 grams / mol (Component El).

23. The modeling material formulation of any one of claims 1 to 22, wherein a total amount of said Component E ranges from 5 to 15, or from 5 to 12, % by weight, of the total weight of the formulation.

24. The modeling material formulation of any one of claims 1 to 23, wherein said Component A comprises at least one hydrophilic mono-functional (meth) acrylate featuring said Tg (Component Al).

25. The modeling material formulation of claim 24, wherein said Component A further comprises at least one hydrophobic mono-functional (meth)acrylate featuring said Tg (Component A2).

26. The modeling material formulation of claim 25, wherein a total amount of Component Al and Component A2 ranges from 15 to 25, or from 20 to 25, % by weight of the total weight of the formulation.

27. The modeling material formulation of any one of claims 1 to 26, further comprising at least one mono-functional (meth)acrylate featuring, when hardened, Tg lower than 80 ° C, or in a range of from 0 to 80, or from 0 to 50, °C (Component B).

28. The modeling material formulation of claim 27, wherein said Component B comprises a hydrophobic mono-functional (meth)acrylate featuring said Tg (Component Bl) and / or an epoxy-type mono-functional (meth)acrylate featuring said Tg (Component B2).

29. The modeling material formulation of any one of claims 1 to 28, further comprising at least one multi-functional (meth) acrylate featuring, when hardened, Tg lower than 80, in a range of from 0 to 80, °C (Component F).

30. The modeling material formulation of claim 29, wherein said Component F has a MW higher than 500, or higher than 1,000, or in range of from 1,000 to 2,000, grams / mol.

31. The modeling material formulation of claim 29 or 30, wherein said Component F is a multi-functional urethane (meth) acrylate featuring, when hardened, said Tg and having a MW lower than 2,000 grams / mol (Component F2).

32. The modeling material formulation of claim 31, wherein said Component F2 features, when hardened, Tg lower than 50, or lower than 20, or in a range of from 0 to 50 or from 0 to 20, °C.

33. The modeling material formulation of claim 31 or 32, wherein an amount of said Component F2, if present, ranges from 10 to 25 % by weight of the total weight of the formulation.

34. The modeling material formulation of any one of claims 29 to 33, wherein said Component F comprises at least one epoxy-type multi-functional (meth) acrylate (Component Fl).

35. The modeling material formulation of claim 34, wherein said Component Fl has MW in a range of from 1,000 to 2,000 grams / mol and / or features, when hardened, Tg higher than 50, or in a range of from 50 to 80, °C.

36. The modeling material formulation of any one of claims 34 to 35, wherein an amount of said Component Fl, if present, ranges from 5 to 20, or from 5 to 15, or from 10 to 15, % by weight, of the total weight of the formulation.

37. The modeling material formulation of any one of claims 29 to 36, wherein said Component F comprises at least one multi-functional urethane (meth) acrylate featuring, when hardened, said Tg and having a MW higher than 2,000 grams / mol (Component F3) and / or a trifunctional urethane (meth)acrylate featuring, when hardened said Tg and having MW higher than 2,000 grams / mol (Component F4).

38. The modeling material formulation of claim 37, wherein an amount of said Component F3, if present, ranges from 1 to 10, or from 3 to 8, or from 3 to 5, % by weight, of the total weight of the formulation.

39. The modeling material formulation of claim 37, wherein an amount of said Component F4, if present, ranges from 1 to 5, or from 1 to 3, % by weight, of the total weight of the formulation.

40. The modeling material formulation of any one of claims 1 to 39, further comprising a dispersant (Component H).

41. The modeling material formulation of claim 40, wherein said dispersant comprises a dispersant that features curable groups (Component Hl) and / or a non-curable dispersant (Component H2).

42. The modeling material formulation of claim 41, wherein an amount of said Component Hl, if present, ranges from 0.5 to 1.5, or is about 1, % by weight of the total weight of the formulation.

43. The modeling material formulation of claim 41, wherein an amount of said Component H2 is at least 0.1, or ranges from 0.1 to 1, or from 0.1 to 0.5, % by weight of the total weight of the formulation.

44. The modeling material formulation of any one of claims 1 to 43, further comprising at least one photoinitiator (Component J).

45. The modeling material formulation of claim 44, wherein an amount of said photoinitiator ranges from 1 to 5, or from 1 to 3, % by weight, of the total weight of the formulation.

46. The modeling material formulation of any one of claims 1 to 45, further comprising a colorant.

47. The modeling material formulation of claim 46, wherein said colorant comprises a paste that comprises a dye or a pigment and mixture of mono-functional and multi-functional curable materials.

48. The modeling material formulation of any one of claims 1 to 47, comprising at least:said Component A, in a total amount of from 15 to 25 % by weight of the total weight of the formulation;said Component C, in a total amount of from 17 to 23, or of about 20, % by weight of the total weight of the formulation;said Component D, in a total amount of from 10 to 30, or from 10 to 20, % by weight, of the total weight of the formulation; andsaid Component E, in a total amount of from 5 to 15, % by weight of the total weight of the formulation.

49. The modeling material formulation of any one of claims 1 to 48, being a transparent formulation which provides a transparent hardened material.

50. The modeling material formulation of claim 49, being a colorless transparent formulation or a colored transparent formulation, which further comprises a transparent dye or pigment.

51. The formulation of any one of claims 1 to 48, being an opaque formulation which comprises an opaque pigment or dye.

52. The modeling material formulation of claim 51, being a white opaque formulation or a colored opaque formulation.

53. The modeling material formulation of any one of claims 1 to 52, featuring, when hardened, impact resistance (Izod XY notched impact resistance) of at least 40 J / m.

54. A method of additive manufacturing a three-dimensional object, the method comprising sequentially forming a plurality of layers in a configured pattern corresponding to the shape of the object, thereby forming the object,wherein the formation of each of at least a few of said layers comprises dispensing at least one formulation, and exposing the dispensed formulation to irradiation to thereby form a hardened modeling material,wherein said at least one formulation is the modeling material formulation as defined in any one of claims 1 to 53.

55. The method of claim 54, wherein said dispensing is further of an additional modeling material formulation.

56. The method of claim 55 wherein said modeling material formulation and said additional modeling material formulation form a digital material and / or a shelled structure.

57. The method of any one of claims 54 to 56, wherein the three-dimensional object comprises in at least a portion thereof a hardened material that exhibits impact resistance (Izod XY notched impact resistance) of at least 40 J / m.

58. A three-dimensional object obtained by the method of any one of claims 54 to 57.

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