Additive manufacturing composition and method

Abstract

To provide an additive manufacturing composition that includes a thermosetting material including a crosslinkable component, and an initiator for free radical crosslinking.SOLUTION: A thermosetting composition includes a crosslinkable component such as a vinyl ester and / or an unsaturated polyester, and an initiator component such as cumene hydroperoxide or BPO or a blend of cumene hydroperoxide and methyl ethyl ketone peroxide. The composition is suitable for use in additive manufacturing to form objects such as molds or prototypes.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of the filing date and priority of U.S. Provisional Application No. 62 / 854,857, filed May 30, 2019, which is incorporated herein by reference.

[0002] Joint Research Agreement Aspects of the present invention have been made by or on behalf of the following parties under a joint research agreement. The joint research agreement was carried out on or before the date on which the aspects of the present invention were made, and the aspects of the present invention were made as a result of activities carried out within the scope of the joint research agreement. The parties to the joint research agreement are Polynt Composites USA Inc. and UT - Battelle, LLC.

[0003] Field This application generally relates to additive manufacturing compositions and methods. In particular, the compositions and methods include thermosetting materials for making objects by additive manufacturing.

Background Art

[0004] Background Additive manufacturing, also known as three - dimensional (3D) printing, is used in a wide range of industries for the manufacture of objects. The additive manufacturing can be carried out using similar feed materials that transfer from a polymeric, alloy, powder, wire, or solid component that cures from a liquid or granular state. Additive manufacturing can be used to rapidly and efficiently manufacture three - dimensional objects layer by layer. Polymer-based additive manufacturing is currently achieved by supplying a polymer material through a nozzle that is precisely positioned over a floor or other support. An object is manufactured by the sequential deposition of layers of material on top of previously deposited layers. Large-scale polymer-based additive manufacturing of objects requires consideration of local heating and temperature gradients that can damage materials designed for 3D printing due to warping or other deformations. Depending on the application, an oven is used to enclose and control the temperature of 3D printing, but the use of an oven increases the complexity, cost, and flexibility of large-scale additive manufacturing. It is desirable to perform polymer additive manufacturing outside of an oven, but in the ambient environment, many polymer materials for additive manufacturing are not suitable for out-of-oven printing. Therefore, there is a continuing need for improvement in additive manufacturing materials and methods.

[0005] Additive manufacturing techniques and processes generally involve the accumulation of one or more materials to create an object, as opposed to subtractive manufacturing methods. Additive manufacturing techniques have the ability to fabricate complex components from a wide variety of materials. In general, self-standing articles can be fabricated from computer-aided design (CAD) models. Polymer additive manufacturing generally involves forming and extruding beads of a flowable material (such as a molten thermoplastic material), depositing the beads of the material in layers to form a replica of an object, and machining the replica to produce a final product. This process is generally accomplished using an extruder mounted on an actuator with controlled movement along at least the X, Y, and Z directions. The extruder deposits beads of the flowable material at precise locations in the X-Y plane to form a layer and then moves in the Z direction to begin forming the next layer. Optionally, a flowable material, such as a molten thermoplastic material, can be injected with a reinforcing material (such as a fiber strand) to increase the strength of the material. Since the flowable material is generally hot and flexible, it can be deposited on a substrate (such as a mold), pushed down or otherwise flattened to some extent, and preferably leveled to a consistent thickness using a roller mechanism corrected in the tangential direction. This flattening process can help fuse a new layer of the flowable material to the layer of the flowable material deposited previously. Optionally, a diaphragm can be used to flatten the beads of the flowable material to a desired thickness, which can result in fusion to the layer of the flowable material deposited previously. By repeating the deposition process, successive layers of the flowable material can be deposited on the existing layers to construct and manufacture the desired object. The new layer of the flowable material is deposited at a temperature sufficient to allow melting of the new layer of the flowable material and fusion with the layer of the flowable material deposited previously, thus creating a solid portion.

[0006] Polymer additive manufacturing has generally utilized thermoplastic polymers. When fabricated from polymers, the mechanical strength of thermoplastic polymers typically increases with molecular weight and degree of branching of the side chains. Unfortunately, this also results in an increase in melt viscosity and melting point. Fused deposition manufacturing (FDM) requires that the layers maintain tolerance immediately after deposition while providing structural adhesion to subsequent layers. This structural adhesion is formed by physically pushing the polymer to melt into the previous layer. Therefore, the resistance to melt flow is an important parameter, and the extrusion of high-strength thermoplastics requires elevated temperatures that exacerbate thermal deformation. U.S. Patent Application Publication No. 20150291833 to Kunc et al. discusses methods and compositions for additive manufacturing that include reactive or thermosetting polymers such as urethane and epoxy resins. These polymers are melted, partially cross-linked prior to deposition, deposited to form a constructed object, solidified, and fully cross-linked, for example, at a point in time or temperature T2 by a downstream curing element. These polymers form a network of chemical bonds spanning the deposited layers.

[0007] Publication No. WO2016086216A1 of Sand Int’l discusses an additive manufacturing method in which thixotropic thermosetting polymer beads are deposited and cured by exposure to visible or non-visible light, UV irradiation, IR irradiation, electron beam irradiation, X-ray irradiation, or laser irradiation. Sand Int’l Publication No. WO2016191329A1 discusses an additive manufacturing apparatus for preparing a three-dimensional structure, as well as related methods, nozzle assemblies, and three-dimensional structures. This additive manufacturing apparatus can include a first container configured to receive a first thermosetting resin component and a second container configured to receive a second thermosetting resin component. A nozzle assembly can be fluidly connected to the first and second containers and configured to receive the first thermosetting resin component and the second thermosetting resin component, and the nozzle assembly can include a mixing assembly configured to mix the first thermosetting resin component and the second thermosetting resin component to form a multi-component thermosetting resin. This additive manufacturing apparatus can further include a build platform configured to receive one or more layers of the multi-component thermosetting resin and form a three-dimensional structure. The nozzle assembly can be configured to extrude the multi-component thermosetting resin onto the build platform.

[0008] Jones U.S. Patent Application Publication No. 20120261060 discusses a polymerizable resin impregnated in a fabric for the purpose of creating a composite material that generates little heat during curing so as to extend the mold life. They claim a relationship between the heat of polymerization such that the rise is less than 60°C and the adiabatic temperature rise of the composite material. Duty et al. U.S. Patent Application Publication No. 20170057160 discusses manufacturing components, methods, and apparatuses for advanced manufacturing including a nozzle for extruding a working material, where the polymeric working material includes carbon fiber reinforced polymers. The construction of the component is performed at atmospheric temperature on a working surface. Duty et al. U.S. Patent Application Publication No. 20180311891 discusses an additive manufacturing method and component having a filling layer material injected into voids as a Z-direction liquid nail or pin for providing better interlayer connection. Instead of depositing a finished layer, the extruder stops extruding at a specific section of the layer leaving a void.

[0009] Kishore et al., Additive Manufacturing 14 (2007) 7-12 states that the strength of the printed part across the continuous layers in the build direction (z-direction) can be significantly lower than the corresponding in-plane strength (x-y direction), and has considered the use of infrared heating to raise the surface temperature of the printed layer just prior to the deposition of new material to improve the inner layer strength of the part. Sudbury et al., Int J Adv Manuf Technol. (2017) 90:1659-1664 discusses a project whose aim was to evaluate the ability to create molds for these small-scale production processes using large-area additive manufacturing, generally known as 3D printing, and use them to hand lay-up composite materials. Large objects made by polymer additive manufacturing continue to face many technical challenges, including the problem of printing and curing thermosetting materials without preheating or secondary exposure to energy for complete curing.

Summary of the Invention

[0010] Summary In one aspect of the present invention, an additive manufacturing composition is provided. The additive manufacturing composition includes a thermosetting material including a crosslinkable component; and a free radical crosslinking initiator. When the composition is deposited in a series of layers, the composition cures without substantial deformation (e.g., warping). In some embodiments of the additive manufacturing compositions and methods, the composition has a peak exotherm temperature of 50 °C or less during curing as one or more deposited layers (including when curing as multiple deposited layers), and / or a peak exotherm temperature of 80 °C or less during curing as a cylindrical mass. The peak exotherm during curing as a deposited layer is measurable by thermal imaging as described in Example 4. The peak exotherm during curing as a cylindrical mass is measurable by the cup peak exotherm procedure as described in Example 7. When the composition is curing, the composition exhibits a peak exotherm that is not more than 40 °C above, alternatively not more than 35 °C above, the temperature at which the composition begins to cure, or alternatively the composition has an enthalpy change rate of 9.0 J / g-min or less, alternatively 8.0 J / g-min or less, alternatively 7.1 J / g-min or less, alternatively less than 6.0 J / g-min. In some embodiments, prior to and / or during curing, the composition is substantially free of gas voids.

[0011] In another aspect, an object comprising a plurality of layers is prepared by curing the novel additive manufacturing compositions described herein. In some embodiments, at least one of the layers has a length of 1.0 m or more in the X direction and / or the Y direction, and / or the object comprises at least 10 layers. In yet another aspect, a method of additive manufacturing an article is provided. The method includes depositing a first layer of a thermosetting material on a support at a deposition temperature. The method also includes curing the first layer of the thermosetting material, wherein the peak exotherm temperature during curing is not more than 40 °C above, alternatively not more than 35 °C above, alternatively not more than 30 °C above the deposition temperature. The method can also include depositing a second layer of the thermosetting material on the first layer opposite the support, during which the first layer undergoes an exothermic reaction and the first layer releases heat to the second layer. The method can include depositing a third layer of the thermosetting material on the second layer and opposite the first layer and the support; curing the thermosetting material deposited as the third layer; and optionally depositing and curing additional layers until a desired height of the object is achieved.

[0012] In some embodiments, the method includes applying a first series of layers having an average peak thermal temperature (MPT) during curing; depositing a second series of layers, wherein the MPT of the second series of layers is within 25 °C of the MPT of the first series of layers. The first series of layers releases heat to the second series of layers. The depositing step may include depositing a thermosetting material to obtain a layer having a thickness of 1.27 to 12.7 mm. Curing of the thermosetting material may occur at atmospheric temperature, or at a temperature of 20 °C to 50 °C, and can be performed without applying secondary energy. The present disclosure may be better understood from the following detailed description when read in conjunction with the accompanying drawings. The figures are not necessarily to scale.

Brief Description of the Drawings

[0013]

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Modes for Carrying Out the Invention

[0014] Detailed Description In one aspect, the present invention provides an additive manufacturing composition comprising a thermosetting material containing a crosslinkable component and an initiator for free radical crosslinking. The thermosetting material and the initiator are selected such that the composition cures without substantial deformation (e.g., warping) when the composition is deposited within a series of layers. In another aspect, a method for additive manufacturing an object is provided. The method includes depositing a first layer of a thermosetting material on a support at a deposition temperature; and curing the first layer of the thermosetting material, wherein the peak temperature during curing is not higher than 40 °C above the deposition temperature, alternatively not higher than 35 °C above the deposition temperature, alternatively not higher than 30 °C above the deposition temperature. In some embodiments, the peak exotherm is 25 °C or less. The method can also include depositing a second layer of the thermosetting material on the first layer opposite the support, during which the first layer undergoes an exothermic reaction and the first layer releases heat to the second layer. After depositing a third layer of the thermosetting material on the second layer and opposite the first layer and the support, additional fourth, fifth, and more layers can be deposited on the previous layer until the desired height of the object is achieved. In some embodiments, the method includes depositing a first series of layers that have an average peak exotherm temperature (MPT) during curing. The method also includes depositing a second series of layers, wherein the MPT of the second series of layers is within 25 °C of the MPT of the first series of layers, and the first series of layers releases heat to the second series of layers. The deposition step can include depositing the thermosetting material to obtain a layer having a desired thickness, e.g., a thickness of from about 1.27 to about 12.7 mm.

[0015] In the present compositions and methods, the heat generation rate and the rate of change of enthalpy are limited, thereby reducing, minimizing or eliminating the deformation and warping of the objects made with the present compositions and methods. More specifically, an additive manufacturing composition having a rate of change of enthalpy of 9.0 J / g-min or less will produce parts that are free of, or substantially free of, deformation or warping. Conversely, parts made with a composition that generates an enthalpy greater than 9.0 J / g-min will exhibit some warping. Control of the rate at which the enthalpy changes or heat is generated can be achieved by the selection of initiators, heat generation inhibitors, catalysts, and antioxidants. As demonstrated in the examples below, there are many combinations of these selections for controlling the heat of polymerization to 9.0 J / g-min or less. In some embodiments, the composition has a heat of polymerization that does not exceed 183 J / g, alternatively 156 J / g, alternatively 140 J / g.

[0016] The change in enthalpy and heat generation can be measured by thermodynamic analysis, such as differential scanning calorimetry (DSC). Prior to curing, the sample is sealed in a sample container and subjected to the same temperature conditions as an empty reference container. The energy difference required to maintain the sample container and the reference container at the same temperature is recorded as a function of temperature. This released or absorbed energy is a measure of the change in enthalpy (ΔΗ) of the sample relative to the reference, and more specifically, the change in the internal energy of the sample. Generally, enthalpy corresponds substantially to heat or internal energy, although enthalpy may differ from internal energy if the sample undergoes a change in pressure or volume. If significant changes occur, such as when curing in a closed volume releases gas, the measured value of enthalpy can be adjusted according to the following equation. H = U + pV Where H is enthalpy, U is internal energy, p is pressure, and V is volume. When curing is carried out at atmospheric pressure, this adjustment is generally not necessary.

[0017] The rate of change of enthalpy during curing refers to the average ratio obtained by dividing the enthalpy that has changed from the substantial start to the end of the curing of the composition by the length of that time. The selection of the start and end points in DSC measurement conforms to the deviation from the baseline and the occurrence along the baseline, based on experience and the shape of the curve as specified. The amount of thermal energy imparted in the art is the total energy under the curve. In some embodiments, the additive manufacturing composition is substantially void-free. Unexpectedly, the presence of voids affected the rate of change of enthalpy and the rate of warping. Tests showed that the heat generation per minute decreased when the gaseous voids were eliminated from the printed part. Objects made of non-porous materials did not show warping. This is counterintuitive because the higher the density of the thermosetting mixture, the more unsaturation per unit volume. By eliminating gas-filled voids from the cured part, it is thought that thermal expansion is reduced, thereby reducing the absolute change in volume from maximum expansion to maximum contraction. This change is represented in the art as "shrinkage" (see enthalpy measurements in FIGS. 4 vs. 5 and shrinkage and total compression measurements in FIG. 6). Thus, in some embodiments, the composition comprises voids of 10% or less, alternatively 5% or less, alternatively less than 4.1% by volume.

[0018] The compositions and methods disclosed herein are adapted for making objects by additive manufacturing. As used herein, "additive manufacturing" refers to making an object by adding material rather than removing material, such as by building one layer on top of the previous layer, and encompasses various manufacturing and prototyping techniques known by various names, including freeform fabrication, 3D printing, rapid prototyping / tooling, etc. Additive manufacturing can also refer to any method by which an object is made by depositing layers on a deposition layer. Each layer will have the desired dimensions and shape such that several layers together form a three-dimensional engineering structure. As used herein, "object" includes manufactured articles made by additive manufacturing, preferably polymer composites, such as polymer composites made by large-scale additive manufacturing. It is contemplated that replicas of objects can be made using additive manufacturing and that the objects can be finished using other techniques, including subtractive techniques such as machining, yet still be made by additive manufacturing. In some embodiments, the article includes a plurality of layers, such as at least 10 layers, or at least 20 layers, or at least 100 layers, or even more layers.

[0019] Large-scale additive manufacturing is different from small-scale (e.g., desktop) 3D printing in several respects. Large-scale additive manufacturing generally has dimensions on the order of feet or meters rather than inches or centimeters. For example, the present methods and compositions can be used to provide objects having a size greater than 1 cubic meter. The build size may refer to the volume defined by the outer boundaries of the object. For example, a square with open ends having sides that are 2 m long and 3 m high has a build size of 12 m 3 even if the interior of the square is hollow. Large-scale additive manufacturing may refer to manufacturing objects having a build size of at least 1 m in length in the X and / or Y directions, or at least 1 cm in height in the Z direction, or at least 0.01 m 3 in size.

[0020] In this method, additive manufacturing generally involves depositing layers or beads of a crosslinkable thermosetting component, usually in a continuous or semi - continuous manner. As used herein, the term "depositing" includes placing, i.e., applying, spraying, extruding, coating, spreading, or other techniques, a composition or material at a desired location. The machine can deposit a plurality of beads to form a layer. In some embodiments, an initial layer is deposited on a floor or support, and subsequent layers are deposited on top of the initial layer. The initial layer can be deposited in the X - Y direction, and then the subsequent layers are deposited in the same X - Y direction but at different positions along the z - direction. The initial layer may begin to cure before the subsequent layer is deposited on it. This can be a function of the moving speed of the nozzle in the X - Y direction. The initial layer will be at the deposition temperature when it is applied to the support. For thermosetting materials, the curing reaction with heat release releases energy and causes a temperature rise, so the temperature will increase as the layer begins to cure. In some embodiments, the temperature of the initial layer does not rise more than 40 °C, alternatively more than 30 °C, alternatively more than 25 °C above its deposition temperature while curing, or has a peak exothermic temperature of 50 °C or less, or 45 °C or less, or 40 °C or less as measured by thermal imaging (exemplified in Example 4 below). In some embodiments, the temperature of the initial layer has a peak exothermic temperature of 80 °C or less during curing as measured by the cup - peak exothermic procedure (exemplified in Example 7 below). Alternatively, the initial layer has a cup - peak exotherm of 75 °C, 72 °C, 68 °C, 67 °C or 65 °C or less during curing. In some embodiments, the composition exhibits a peak exotherm that is not more than 40 °C, or 35 °C, or 30 °C, or 25 °C above the temperature at which the composition begins to cure. In some embodiments, the composition has an enthalpy change ratio of 9.0 J / g - min or less, alternatively 8.0 J / g - min or less, alternatively 7.1 J / g - min or less, alternatively 6.0 J / g - min or less.

[0021] A thermosetting material is deposited and, after it begins to cure, the next layer of thermosetting material is applied to the cured layer. The curing layer heats the next layer and raises its temperature as it begins to cure. This heat transfer from the first layer to the next layer continues as the layers are deposited. The exothermic properties of the present method and composition can be characterized by Peak Exo and / or Total Time to Peak (TTP). Peak Exo is generally the highest temperature reached by the sample during curing, or Peak Exo may be represented as the difference between the peak point and the temperature at which the sample begins to cure or is deposited. In some embodiments, a combination of a thermosetting material and an initiator is selected with process parameters to maintain a Peak Exo temperature of 50 °C or less. In some embodiments, the composition or method has a Peak Exo temperature of 50 °C or less, alternatively 45 °C or less, alternatively 42 °C or less, alternatively 40 °C or less, alternatively 38 °C or less, alternatively 37 °C or less, alternatively 35 °C or less during curing. The foregoing Peak Exo temperatures occur when a preferred embodiment of the present composition is deposited and cured during additive manufacturing. The Peak Exo of individual layers deposited by additive manufacturing can be measured by thermographic imaging or other suitable techniques. Alternatively, the present method and composition can have a Cup Gel Peak Exotherm that is 80 °C, 75 °C, 72 °C, 68 °C, 67 °C or 65 °C or less during curing. In some embodiments, the present composition and method have a time to Peak Exo of 70 minutes or less, alternatively 60 minutes or less, alternatively 50 minutes or less, alternatively 40 minutes or less.

[0022] The present composition and method can accommodate the thermal and physical stresses of additive manufacturing of large objects while providing advantages over existing thermosetting technologies by reducing cost and complexity. An additive manufacturing system or machine for forming an object based on one layer at a time includes a nozzle fluidly connected to a thermosetting component source and a motion control system connected to the nozzle for moving the nozzle in a predetermined pattern to form a layer of the component. In some embodiments, the additive manufacturing system further includes one or more pumps for pumping a thermosetting material (or one or more components of a thermosetting material). The additive manufacturing system can further include a mixer for receiving and mixing one or more components of the thermosetting material. The system can also further include a controller for controlling the rate and / or temperature at which a layer of the thermosetting material is deposited. The method can include varying the temperature of the beads of the thermosetting material deposited at a temperature that controls the apparatus.

[0023] In some embodiments, the rate at which a fluid material is deposited during additive manufacturing is determined based on one or more of the gelation time, peak exotherm, and time to deposit a layer. Individual extruded beads are significantly larger (e.g., about 0.75 inches (1.9 cm)) in a small-scale additive manufacturing system. The deposition rate can be at least 10 cm 3 / hour, or up to 50 L / hour. In some embodiments, the method enables manufacturing outside of a chamber or oven that provides a temperature increase relative to the ambient temperature at the ambient temperature. The method can be performed on a heated bed that provides a temperature increase by contact without requiring a temperature increase in the surrounding space. The method and the composition enable the manufacture of large objects by additive manufacturing, for example by using a thermosetting material, without significant deformation of the object or stress between layers. As used herein, the term "deformation" refers to an undesirable difference from an intended or desired physical structure or form and includes warping, distortion, buckling, bending, or other deformations. In some embodiments, surprisingly, deformation can be avoided without using shrinkage additives typically included in thermosetting materials, but rather by reducing or limiting the temperature difference between layers, for example by selecting crosslinkable components, initiators, and process parameters.

[0024] This composition contains one or more crosslinkable components, such as vinyl ester components, unsaturated polyester components, and / or urethane acrylate components. The unsaturated polyester component is generally produced by a condensation reaction of an unsaturated dicarboxylic acid or polycarboxylic acid or anhydride with a glycol and / or polyhydric alcohol, and may optionally be accompanied by a saturated dicarboxylic acid or polycarboxylic acid or anhydride. The bifunctional or polyfunctional organic acids or anhydrides that can be used are any of many known compounds. Suitable bifunctional and polyfunctional acids or their anhydrides include, but are not limited to, maleic acid and anhydride, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid and anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, cyclohexanedicarboxylic acid, succinic anhydride, adipic acid, sebacic acid, azelaic acid, malonic acid, alkenyl succinic acid, such as n-dodecenyl succinic acid, dodecyl succinic acid, octadecenyl succinic acid, and their anhydrides. Any of the lower alkyl esters of the above can also be used. Any mixture of the above is also suitable, and there are no intended restrictions in this regard.

[0025] Furthermore, polyfunctional acids or their anhydrides having three or more carboxylic acid groups may be used. Such compounds include 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,3,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-carboxymethylpropane, tetra(carboxymethyl)methane, 1,2,7,8-octanetetracarboxylic acid, citric acid, and mixtures thereof. Suitable dihydric and polyhydric alcohols that can be used to form the unsaturated polyester component include, but are not limited to, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,3-hexanediol, neopentyl glycol, 2-methyl-1,3-pentanediol, 1,3-butylene glycol, 1,6-hexanediol, hydrogenated bisphenol A, cyclohexanedimethanol, 1,4-cyclohexanol, ethylene oxide adduct of bisphenol, propylene oxide adduct of bisphenol, sorbitol, 1,2,3,6-hexatetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methyl-propanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxyethylbenzene. Mixtures of any of the above alcohols can be used.

[0026] The vinyl ester component is produced by ring-opening of an epoxy resin with an unsaturated monocarboxylic acid. In some embodiments, the vinyl ester component is prepared by reaction between a vinyl-containing organic acid such as methacrylic acid and an epoxide-containing intermediate in the presence of a catalyst. In some embodiments, the vinyl ester resin is produced from diglycidyl ether of bisphenol A (DGEBA) and methacrylic acid, or from the reaction between glycidyl methacrylate and a polyfunctional phenol. Any number of epoxides can be used in the present invention. Preferably, the polyepoxides include, but are not limited to, glycidyl methacrylate, glycidyl polyethers of both polyhydric alcohols and polyhydric phenols, bisphenol A epoxy, bisphenol F epoxy, glycidyl esters of neodecanoic acid, flame-retardant epoxy resins based on tetrabromobisphenol A, epoxy novolac, epoxidized fatty acids or drying oleic acids, epoxidized diolefins, epoxidized unsaturated acid esters, and epoxidized unsaturated polyesters. The above mixtures may be utilized. The polyepoxide may be a monomer or a polymer. Particularly preferred polyepoxides are glycidyl ethers of polyhydric alcohols or polyhydric phenols having from about 150 to about 1500, more preferably from about 150 to about 1000 equivalents per epoxy group. Typically, the epoxy resin is based on bisphenol A (equivalent 180 - 500), and the monocarboxylic acid is methacrylic acid. Acrylic acid and derivatives can also be used. Novolac epoxy and blends of novolac epoxy and bisphenol A epoxy can also be used. Typically, the components react in a ratio of 1 equivalent of epoxy resin to 1 mole of acid. An example of a vinyl ester is bisphenol A glycidyl methacrylate obtained by reacting bisphenol A epoxy resin with methacrylic acid.

[0027] In some embodiments, the composition comprises a core-shell rubber-modified vinyl ester resin. As used herein, "core-shell rubber-modified vinyl ester resin" means a vinyl ester resin and a core-shell polymer in which a core-shell polymer having a rubbery core is dispersed throughout the vinyl ester resin. Suitable vinyl ester resins include the vinyl ester components described above. Core-shell polymers are generally produced by controlled emulsion polymerization in which the feed of monomer composition is varied during polymerization to achieve the desired compositional variation across the structure of the core-shell polymer. Although many core-shell polymers with a wide variety of properties are available, core-shell polymers suitable for use in the present composition typically have a core that is rubbery at ambient conditions and are produced by polymerizing monomers such as butadiene and alkyl acrylates. "Rubbery at ambient conditions" is understood to mean that the core of the core-shell polymer has a Tg below ambient temperature. Preferred core-shell polymers include, but are not limited to, the following polymerization types: butadiene; butadiene and styrene; butadiene, methyl methacrylate and styrene; butadiene, alkyl methacrylate, and alkyl acrylate; butadiene, styrene, alkyl acrylate, alkyl methacrylate and methacrylic acid; butadiene, styrene, alkyl acrylate, alkyl methacrylate, methacrylic acid and low molecular weight polyethylene (as a flow modifier); butyl acrylate and methyl methacrylate; alkyl methacrylate, butadiene and styrene; alkyl acrylate, alkyl methacrylate and glycidyl methacrylate; and alkyl acrylate and alkyl methacrylate. The core-shell polymer can have an average diameter of 50 - 350 nm; alternatively, 100 - 300 nm; alternatively, 150 - 250 nm; alternatively, about 200 nm; alternatively, 200 nm. A typical core-shell polymer used in the present composition incorporates butadiene as the core component and poly(methyl methacrylate) (PMMA) as the shell component. The core-shell polymer can be amine-terminated butadiene nitrile rubber (ATBN) nanoparticles.

[0028] In some embodiments, the composition includes a reactive impact modifier component. An impact modifier is an additive that improves the impact strength of a material. The impact modifier can improve the impact strength of an additive manufactured product produced from beads or particles by at least 10%, for example at least 20% or 30%, compared to one that does not contain the impact modifier. Typically, the improved impact strength as described above is measured by the notched Izod impact strength according to the method described in ASTM D256 or ISO180. In the impact-modified polymer beads of the present invention, the impact modifier can form an elastomeric region within the beads. Specifically, in the case of core-shell impact-modified beads, the impact modifier can form a discontinuous elastomeric phase within the beads, and the acrylic or vinyl (co)polymer matrix forms a continuous phase within the beads. Further, in addition to or instead of the formation of the elastomeric region itself, the impact modifier can be polymerized in the acrylic or vinyl (co)polymer to form an elastomeric region within the polymer chain. Furthermore, the impact modifier can crosslink the matrix (co)polymer to provide an elastomeric region within the resulting network structure or form branches of the matrix (co)polymer. Suitable impact modifiers for aspects of the present invention are known to those skilled in the art and include, but are not limited to, core-shell, oligomers, reactive oligomers, and (co)polymers. Suitable impact modifiers can include random, block, radial block, dendrimer, branched, and / or graft polymer types. In some embodiments, the impact modifier is selected from acrylic (e.g., n-butyl acrylate-styrene), styrene (e.g., MBS and SBR), silicone (including silicone-acrylic), nitrile rubber, isoprene, butadiene, isobutylene, and aliphatic polyurethane, polyether oligomer, polyester oligomer modifiers. Typically, the impact modifier can be an acrylic, butadiene, aliphatic polyurethane, or silicone-acrylic impact modifier.

[0029] In some embodiments, the composition comprises a urethane acrylate component. As used herein, "urethane acrylate" means the reaction product of a diisocyanate, an -OH functional molecule having a crosslinkable olefin double bond, and an optional monofunctional, difunctional, or polyfunctional -OH containing substance. As used herein, "diisocyanate" means any type of aromatic, aliphatic, cycloaliphatic, and aromatic-aliphatic polyisocyanate, including dimers and trimers having two or more isocyanate groups on each molecule. Typical aromatic polyisocyanates include diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI). Typical aliphatic polyisocyanates include hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). Examples of "-OH functional molecules having a crosslinkable olefin double bond" include partial esters of polyhydric alcohols and acrylic acid or methacrylic acid, such as ethylene glycol monoacrylate or monomethyl acrylate, 1,2- or 1,3-propanediol monoacrylate or monomethyl acrylate, 1,4-butanediol monoacrylate or monomethyacrylate, 1,6-hexanediol monoacrylate or monomethacrylate, trimethylolpropane diacrylate, glycerol diacrylate, pentaerythritol triacrylate, and mono(N-methylolacrylamide)-ethers and mono-(N-methylolmethacrylamide)-ethers of ethylene glycol, propylene glycol, butanediol, hexanediol, and neopentyl glycol.Examples of the "monofunctional, bifunctional, or polyfunctional OH-containing substances" include polyhydric alcohols such as diols having 2 to 8 carbon atoms, such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, etc., triols such as glycerol, trimethylolpropane, and hexanetriol, pentaerythritol, etc.; or polyether-polyols prepared by the reaction of one molecule of alcohol with 1 to 50, preferably 15 to 30 molecules of ethylene oxide or propylene oxide. Examples of polyester polyols include polycondensation reaction products of polybasic acids such as adipic acid, succinic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, and terephthalic acid, and polyhydric alcohols such as 1,4-butanediol, 1,3-butanediol, ethylene glycol, diethylene glycol, propylene glycol, 1,2-propylene glycol, dipropylene glycol, 1,6-hexanediol, and neopentyl glycol.

[0030] The composition may further contain one or more additives such as air release / wetting agents, rheology modifiers, thixotropic synergists, inhibitors, initiators, catalysts, surfactants, fillers, and paraffin waxes. The composition may contain a plurality of additives of the same type (e.g., one or more fillers) or a combination of different types of additives (e.g., at least one catalyst and at least one surfactant). When present, the one or more additives may constitute about 0.1% to about 60% of the total mass of the composition; alternatively, about 0.1% to 50%; alternatively, about 0.1% to 40%; alternatively, about 0.1% to 20%, or alternatively, about 0.1% to 15%.

[0031] In some embodiments, the additive manufacturing composition and method have a maximum linear shrinkage, e.g., less than 8.0%, alternatively less than 6.0%, alternatively less than 5.0%, alternatively less than 2.0% linear shrinkage after curing or after formation of the object. In some embodiments, the additive manufacturing composition and method have a maximum total shrinkage, e.g., less than 15.0%, alternatively less than 14.0%, alternatively less than 13.0% total shrinkage after curing or after formation of the object. It is also known that curable compositions tend to shrink when cured and that in some systems this tendency can be reduced or overcome by adding various polymer additives; such additives are called low profile additives (often abbreviated "LPA"). Low shrinkage additives such as polystyrene, styrene-butadiene rubber, etc. are used in various radically polymerizable unsaturated resins. In some embodiments, the composition comprises a low shrinkage agent or shrinkage control additive, and in other embodiments, the composition is essentially free of a low shrinkage agent or shrinkage control additive.

[0032] The composition may further contain one or more ethylenically unsaturated monomers. The ethylenically unsaturated monomer may be any ethylenically unsaturated monomer capable of crosslinking an unsaturated polyester component or a vinyl ester component by vinyl addition polymerization. Typical monomers include, but are not limited to, styrene, methyl methacrylate, vinyl toluene, hydroxymethyl methacrylate, hydroxymethyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, α-methylstyrene, and divinylbenzene. Further typical monomers include o-methylstyrene, m-methylstyrene, p-methylstyrene, methyl acrylate, t-butylstyrene, diallyl phthalate, triallyl cyanurate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate; ethoxylated trimethylolpropane triacrylate; glyceryl propoxytriacrylate; propylene glycol diacrylate; ethylene glycol diacrylate; ethylene glycol dimethacrylate; ethylene glycol diacrylate; tetraethylene glycol diacrylate; triethylene glycol dimethacrylate; tripropylene glycol dimethacrylate; polypropylene glycol diacrylate; polyethylene glycol dimethacrylate (dimeacrylate); butanediol diacrylate; butane-diol dimethacrylate; pentaerythritol triacrylate; pentaerythritol tetraacrylate; ethoxylated bisphenol A diacrylate; hexanediol diacrylate; dipentaerythritol monohydroxypentaacrylate; neopentyl glycol diacrylate; neopentyl glycol dimethacrylate; and tris(2-hydroxyethyl) isocyanurate triacrylate, and mixtures of two or more of the aforementioned polymers. In some embodiments, the monomer is styrene or one of its derivatives. In other embodiments, the composition is substantially free of styrene and / or any of its derivatives.The monomer may constitute 0.1 to about 40% of the total mass of the composition; alternatively, 0.1 to 40%; alternatively, 0.1 to 30%; or alternatively 0.1 to 20%.

[0033] The composition may include a multi-part composition in which each part is separately prepared and then mixed together before use. In these embodiments, the composition includes a first part containing a crosslinkable component; and a second part containing an initiator. The composition may optionally further include a third part containing a monomer or other component. The composition includes a multi-part composition in which each component is separately prepared and then mixed together before or during deposition. In some embodiments, the composition includes a first part containing a crosslinkable component (a second portion of the same crosslinkable component contained in the first part, or a different component) and an accelerator; and a second part containing a crosslinkable component and an initiator. In the multi-part composition, the first part is free of initiator and the second part is free of accelerator, such that crosslinking is desirably avoided or minimized before the first part and the second part are mixed together. In some embodiments, the first part and the second part are supplied or mixed in a ratio of about 1:1, or about 2:1, or about 10:1, or about 20:1, or about 50:1, or another ratio.

[0034] The composition can include an accelerator containing a copper-containing complex; a quaternary ammonium or phosphonium salt; a tertiary amine or phosphine; and / or an optional transition metal salt, as disclosed in Nava's U.S. Patent Application Publication No. 20160096918. In some embodiments, the accelerator includes a component selected from cobalt naphthenate, cobalt octoate, cobalt hydroxide, potassium octoate, potassium naphthanate, manganese salts, iron salts, N,N-dimethylaniline, N,N-dimethyl-p-toluidine; or a combination thereof. The composition or a part thereof may further include one or more additives. Suitable additives include inhibitors, antioxidants, rheology modifiers, air release / wetting agents, colorants, air release agents, inorganic or organic fillers, light fillers, surfactants, inorganic or organic nanoparticles, or combinations thereof. In some embodiments, the composition includes an inhibitor selected from t-butyl catechol, hydroquinone, methyl hydroquinone, monomethyl ether of hydroquinone, copper naphthenate, and triphenyl antimony; or combinations thereof.

[0035] In some embodiments, the additive manufacturing composition includes a rheology modifier that may be selected from silica, clay, organically treated clay, castor oil, and polyamide; or combinations thereof. In some embodiments, the air release / wetting agent is selected from polyacrylate, silicone, and mineral oil; or combinations thereof. In some embodiments, the colorant is selected from iron oxide, carbon black, and titanium oxide; or combinations thereof. In some embodiments, the filler includes an organic or inorganic filler, such as polyethylene, crosslinked polyester, crosslinked acrylic resin, crosslinked urethane, abs, graphite, and carbon fiber; or an organic filler selected from combinations thereof; or an inorganic filler selected from calcium carbonate, clay, talc, wollastonite, fly ash, glass or polymer microballoon, zinc sulfate, nanoclay, nanosilica, nanozinc, and glass fiber; or combinations thereof. In some embodiments, it is advantageous to include one or more shrinkage control additives. However, a further aspect of the present invention is capable of preventing substantial deformation without including shrinkage control additives. Thus, in some embodiments, the method and the composition are essentially free of shrinkage additives such as polyvinyl acetate (PVAc), saturated polyester, PEG-400, PEG-600 diacrylate, styrene butadiene rubber, functionalized polystyrene, polyethylene, and cellulose acetate butyrate (CAB).

[0036] The term "initiator" generally includes compounds referred to by other terms in the polymer industry such as catalysts, curing agents, hardeners, etc., but in certain contexts, one or more of these terms may have different meanings. In addition to initiators, the curing of the present composition can be accelerated using organometallic compounds, UV, electron beams, heat, or peroxide systems. In some embodiments, the curing is carried out using UV light, electron beams, organometallic compounds, peroxides, or heat. In some embodiments, the curing is carried out in an open or unheated environment, i.e., outside an oven or other heating chamber. The open environment may include a floor on which the thermosetting material is deposited, and the floor is heated, but the surrounding environment is not heated for curing purposes and is at a normal room temperature (e.g., about 25°C, or between 22°C and 28°C). In some embodiments, the thermosetting material is deposited on the floor, the material exiting the nozzle has a temperature between 15°C and 30°C, and the floor has a temperature between 15°C and 30°C.

[0037] In some embodiments using a peroxide system as the initiator, the peroxide system can preferably be a peroxide or hydroperoxide at a concentration of 0.5 to 4% by mass. Typical peroxides or hydroperoxides include, but are not limited to, benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, methyl ethyl ketone peroxide (MEKP), t-butyl perbenzoate, etc. In some embodiments, the initiator is selected from cumene hydroperoxide, benzoyl peroxide, or a blend of cumene hydroperoxide and methyl ethyl ketone peroxide and contains peroxide. For example, the initiator can be cumene hydroperoxide. In some embodiments, the composition includes an initiator that induces crosslinking at a slower rate and / or with less exotherm. For example, the initiator may include cumene hydroperoxide or benzoyl peroxide. In some embodiments, the initiator does not include MEKP. The composition of the initiator may be a combination of an initiator, a catalyst, such as a metal salt or complex, and / or other components that induce crosslinking at a slower rate and / or with a lower peak exotherm. In some embodiments, the initiator is adapted so that the composition does not exceed 9.0 J / g-min, instead 8.0 J / g-min, instead 7.1 J / g-min, instead 6.0 J / g-min during curing.

[0038] Functioning at room temperature, examples of the types of initiators that can be used in the present composition and the present method are as follows. a. Organic peroxides, such as cumene hydroperoxide (CHP), benzoyl peroxide (BPO), blends of cumene hydroperoxide and methyl ethyl ketone peroxide (MEKP), peroxydi carbonates, peroxy esters, diacyl peroxides, peroxy ketals, dialkyl peroxides, and hydroperoxides; and inorganic peroxides, ammonium persulfate, sodium hydroxymethanesulfinate dihydrate, potassium persulfate, or sodium persulfate. For example, the peroxide can be BPO, CHP, or a blend of CHP and MEKP. b. Photoinitiators, such as benzoin ethers, benzyl ketals, α-dialkoxyacetophenones, α-hydroxyalkylphenones, α-aminoalkylphenones, acylphosphine oxides, benzophenone / amines, thioxanthone / amines, and titanocenes; c. Azo initiators, such as 4,4′-azobis(4-cyanovaleric acid), 1,1′-azobis(cyclohexanecarbonitrile), azobisisobutyronitrile; 2,2′-azobis(2-methylpropionitrile).

[0039] The additive manufacturing composition can also include a reinforcing material such as synthetic or natural fibers. Polymer composites are often small fibers (glass, carbon, aramid) and thermosetting resins, such as unsaturated polyester, epoxy resin, phenolic resin, polyimide, polyurethane and other combinations. Thermosetting resins can be reinforced with glass fibers, carbon fibers, aramid fibers, basalt fibers (geotextile fibers) or natural fibers. For example, the reinforcing material can be continuous fibers extruded with the thermosetting material or discontinuous fibers dispersed in the thermosetting material, such as a discontinuous material selected from the group consisting of carbon, glass, and aramid. The reinforcing material can be a mixture of two or more of the above reinforcing materials.

[0040] The thermosetting material undergoes curing, which is an exothermic irreversible chemical reaction in which a low molecular weight liquid is converted into a high molecular weight cross-linked solid. When the reaction has proceeded sufficiently so that the thermosetting material has reached a three-dimensional molecular structure that is flexible but does not flow, the intermediate change during curing is gelation. Gelation is achieved by the release of energy, which results in a temperature increase. The material is no longer liquid or fluid. Therefore, the gelation time is a factor in the manufacture of all composites, and the gelation temperature is important for composites with thick or large cross-sections. ISE, the gelation time range of this composition is 10 - 50 minutes, preferably 20 - 25 minutes. The total time to peak energy release is 35 - 70 minutes. The average thickness of the additive manufacturing composition applied by the additive manufacturing system can be 1.27 - 127 mm; alternatively, 2.54 - 63.5 mm; alternatively, 3.81 - 25.4 mm; alternatively, 5.08 - 20.32 mm; alternatively, 5.08 - 19.05 mm; alternatively, 5.08 - 15.24 mm; or alternatively, about 6.35 mm; or alternatively, 6.35 mm to achieve the performance described herein. In some embodiments, the thermosetting material is deposited in an amount sufficient to obtain a layer having a thickness of 0.1016 - 0.254 mm, preferably 0.1524 - 0.127 mm. Further, in some application methods, the composition can be applied as a layer in a single or series of applications to obtain a layer within the range of 0.1016 - 25.4 mm, preferably 0.1524 - 2.032 mm.

[0041] In some embodiments, the method and composition are used to fabricate a substrate as opposed to a coating on a substrate. The cured composition exhibits no or minimal evidence of dimensional changes such as warping. One of ordinary skill in the art will readily appreciate what is meant by no or minimal evidence of dimensional change. A composition cured without substantial deformation may still have some deformation even without unacceptable deformation. For example, acceptable deformation includes deformation of 0.25 inches (0.635 cm) or less, alternatively 1 cm or less, alternatively 0.5 cm or less from the printed or deposited surface. As another example, no or minimal evidence of dimensional change corresponds to a finished product having less than 0.10 mm of warp in a portion that is 914.4 mm (L) × 228.6 mm (H) × 19.05 mm (W). In some embodiments, the composition, when cured, exhibits less than 5% deformation, alternatively less than 2.5% deformation, alternatively less than 1% deformation from the printed or deposited surface. In some embodiments, the composition, when cured, can shrink by more than 8.0%, but there is no substantial deformation of the object made from the composition. Exemplary embodiments of the composition and method had a linear shrinkage of less than 6% but showed no observable deformation. The tests were performed with a TA Ares G2 rheometer.

[0042] The method and composition can be used to make objects of any shape, size, or use. Preferably, the object is a polymer composite. Examples of objects that can be made by the additive manufacturing methods disclosed herein include molds, prototypes, support beams, furniture, core structures, and other objects. While specific embodiments have been described in detail, one of ordinary skill in the art will understand that various modifications and alternative forms are possible in light of the teachings of the present disclosure. In particular, the methods described herein can be utilized in any number of different ways and for a variety of applications that do not necessarily require an object made by additive manufacturing. Accordingly, the disclosure herein is merely exemplary and is not intended to limit the scope thereof, and the full scope of the appended claims and any equivalents thereof should be considered.

Example

[0043] Example 1 In this example, the composition is prepared with the components and steps shown in Table 1 below. More specifically, each composition contains a crosslinkable component (vinyl ester and / or unsaturated polyester, and monomer), a cobalt accelerator, and an amine. The compositions in Table 1 are combined with an initiator to form an additive manufacturing composition, which can be induced to cure.

[0044]

Table 1

[0045] Example 2 In this example, the composition of Example 1 is combined with a second part containing cumene hydroperoxide (CHP) or benzoyl peroxide (BPO) as an initiator.

[0046]

Table 2

[0047] Example 3 In this example, at the Oak Ridge National Laboratory, an object with a vacuum-shaped build size of 91 cm (L) × 91 cm (W) × 18 cm (D) for forming a mold for sanitary ware was fabricated using the composition of Example 2A on a large-area additive manufacturing machine. The crosslinkable component and the initiator component were mixed in the mixer of the additive manufacturing system and supplied to the nozzle. The first layer was deposited on a heated bed having a temperature of 25°C, and the object was formed by depositing a series of layers. The layers were deposited at a deposition temperature of 25°C. The steady-state temperature measured for the thermosetting material was <50°C, and the time to peak exotherm was measured to be 36.1 minutes. The thermosetting material was deposited at a rate of 68.6 mm / second by the nozzle of the system. The temperature of the deposited layers was evaluated, and the results are shown in FIG. 1. The temperature of the first 10 layers was higher than that of the other layers, but it leveled off between layers 15 and 20. In contrast, the additive manufacturing composition containing the "hotter" initiator CHM-50 showed a significantly higher temperature as the layers were deposited, with the temperature of layers 1 to 10 approaching 80°C and exceeding 80°C. FIG. 7 shows the thermal imaging data of the layers deposited with this composition. The additive manufacturing composition containing CHM-50 resulted in an object with unacceptable deformation in a curved form, while the composition of Example 2A had no significant deformation.

[0048] Example 4 In this example, a series of layers of an additive manufacturing composition were deposited using an additive manufacturing system at Oak Ridge, and the temperature of the deposited layers was evaluated. The additive manufacturing composition of Example 2A was deposited at a rate of 68.6 mm / second. FIGS. 1 and 2 show the temperature evaluation of a series of layers of a thermosetting material deposited under two conditions. In FIG. 1, a CHP system with gas voids was deposited, and the maximum temperature difference between layers was 27°C. In FIG. 2, a CHP system substantially without gas voids was deposited, and the maximum temperature difference between layers was 18°C. FIGS. 1 and 2 were provided courtesy of Dr. Vlastimil Kunc and the Manufacturing Demonstration Facility at Oak Ridge National Laboratory.

[0049] Example 5 In this example, a series of layers of an additive manufacturing composition were deposited using an additive manufacturing system at Oak Ridge, and the temperature of the deposited layers was evaluated. The additive manufacturing composition of Example 2A was deposited at a rate of 68.6 mm / second. FIG. 3 shows the ratio of the energy generated during the curing of the composition. FIGS. 4 and 5 show the ratio of the energy generated by an air-containing additive manufacturing composition to a degassed additive manufacturing composition. In FIG. 4, the composition contained gas voids, and the rate of enthalpy change was 6.58 J / g-min. In FIG. 5, the composition was substantially free of gas voids, and the rate of enthalpy change was 5.32 J / g-min. The object manufactured according to FIG. 5 had less deformation than the object of FIG. 4.

[0050] Example 6 This example describes several embodiments of the additive manufacturing composition prepared with the components shown in Tables 3 and 4. More specifically, each composition includes a crosslinkable component (vinyl ester and / or unsaturated polyester, and monomer) and other components. The compositions of Tables 3 and 4 can be combined with an initiator such as CHP or BPO to form an additive manufacturing composition.

[0051]

Table 3

[0052]

Table 4

[0053] It was found that when Composition A was combined with 2.0% CHP, it cured without substantial deformation when deposited in a series of layers. Composition A also cured without substantial deformation with 2.5% CHP. When Composition T was combined with 2.5% LV-40, it cured without substantial deformation when deposited in a series of layers. However, undesirable deformation was observed for Composition T when combined with 2.0% LV-40. Undesirable deformation was observed for Composition A when combined with 1.0% CHM-50.

[0054] Example 7 In this example, several of the additive manufacturing compositions of Example 6 were analyzed to determine the gelation time, cure time, and exotherm at room temperature. More specifically, this example utilized the following procedure to determine the total gelation time and peak exotherm to the peak of the resin that is either promoted or not promoted when catalyzed with a defined oxide. Appropriate safety measures were followed. This example had the ability to run at speeds of 30" (76 cm) / hour or 60" (152 cm) / hour and used a temperature recorder with an accuracy of ±4°F (±2°C) over the range of 0 to 500°F (or 250°C), or equivalent to a J-type thermocouple interface. This example also used a grounded J-type thermocouple, iron-constantan (coated with 6" (15 cm) of stainless steel). A constant temperature water bath maintained at 25 ± 0.2°C using a pipette with a 5 ml capacity graduated in 0.05 ml increments with an accuracy of ±0.05 ml was used to conduct this test, and the ambient environment was maintained at a temperature of 25 ± 2°C. This example followed the following procedure. An amount of resin (50 ± 0.1 grams) was weighed into a 100 ml polypropylene beaker. A metal spatula, wooden tongue depressor, or thermometer was inserted into the beaker. When using a wooden tongue depressor, the pre-weighed resin was used to cover the wooden tongue depressor 1 / 2 inch (1.27 cm) above the resin level to prevent absorption of the cobalt solution, catalyst, or any further additives. The beaker containing the resin was placed in a constant temperature water bath at 25 ± 0.2°C. The resin sample was equilibrated to 25 ± 0.2°C over a sufficient period of time. When using a thermometer to facilitate resin temperature adjustment, the thermometer must remain in the sample until it is completely dispersed after the catalyst has been added. The type and amount of catalyst specified in Table 5 was added to the test resin and thoroughly mixed in the water bath for 1 minute. Air entrapment was avoided during mixing.

[0055] The sample was periodically checked by lifting the spatula or tongue depressor to observe the resin flow rate and watching for signs of gelation. The sample should not be stirred when checking the sample. The point at which the resin stops flowing and the stick can be "snapped off" and returned into the beaker was considered the gelation point, and the elapsed time from catalyst addition to the gelation point was considered the "cup gelation time". The gelation time was recorded, but the time for this example continued to flow. Once the gelation time is reached, immediately remove the beaker from the water bath and place it on a non-thermally conductive surface (i.e., wood). Insert the thermocouple so that the tip of the thermocouple is 3 / 16 inch (0.47625 cm) from the bottom of the beaker and centered within the surface of the resin sample. Observe the time and temperature and consider the elapsed time from catalyst addition to peak temperature as the "total time to peak". Report the maximum temperature reached as the "cup gelation peak exotherm". The cup gelation peak exotherm is different from the peak exotherm measured by thermal imaging of the deposited layer (shown in Figures 1 and 2). The results of this example are shown in Table 5 below.

[0056]

Table 5

[0057] These results demonstrate that some embodiments of this composition exhibit a cylindrical mass peak exotherm (e.g., cup gelation peak exotherm) not exceeding 80 °C when cured in a 50 g mass. In some embodiments, the additive manufacturing composition may have a cup gelation peak exotherm that is 80 °C, 75 °C, 72 °C, 68 °C, 67 °C, or 65 °C or less during curing. These results demonstrate that some embodiments of this composition exhibit a peak exotherm that does not exceed 35 °C, 32 °C, or 30 °C above the temperature at which the composition begins to gel, instead of exceeding 40 °C above that temperature.

[0058] Example 8 In this example, differential scanning calorimetry (DSC) analysis was performed on some of this composition. This analysis procedure is suitable for analyzing thermosetting resins induced to cure and additive manufacturing compositions containing various fillers and additives. This analysis was performed using a TA Instruments Q2000 and / or Q200 DSC (differential scanning calorimeter) and associated Tzero DSC press and Tzero pans with airtight lids. DSC analysis utilized the following steps. Using a disposable plastic pipette, weigh out a minimum of 25 grams of the sample into a 150 ml disposable polypropylene beaker. Using a disposable glass pipette and a squeeze valve, weigh out the appropriate initiator and initiator concentration into the same 150 ml polypropylene beaker. Stir the mixture of the sample and the initiator with a tongue depressor for 2 minutes. Add 4 mg to 20 mg of the sample / initiator mixture to the bottom of a tared DSC pan using a cylindrical wooden applicator stick. Record the weight of the sample. Seal the sample by covering the sample pan using a DSC Tzero press and an airtight seal die set. Load the DSC sealed sample pan / cover and the sealed empty reference pan / cover into the DSC cell on top of their respective sample and reference posts. Close the cell lid and confirm that the auto-sampler of the system has stopped. Confirm that the nitrogen purge gas is set at 50 ml / min. For the Q2000 DSC, confirm that the RCS 90 mechanical cooling device is on. For the Q200 DSC, confirm that the air supply setting to the FACS (fin air-cooled system) is set at 20 psi (1.4×10 5 Pa). Input the sample (and, if applicable, the weight of the pan / cover), the sample ID, and the data file name into the TA Instruments Thermal Advantage software. Confirm that the DSC instrumentation method includes the following parameters: equilibration at 30°C; isothermal hold for 3 minutes; temperature ramp from 30°C to 200°C at 10°C / min; marking the end of the thermal cycle; storage of data. Press the green arrow button in the Thermal Advantage software to start the analysis.

[0059] The results of the DSC analysis were obtained as follows. The heat generation during curing was integrated using TA Instruments Universal Analysis software, and the results were calculated. The heat generation peaks were identified as follows. When using TA Universal Analysis software, the heat generation signal is always upward and has a positive value, while the endothermic signal is always downward and has a negative value. Click the "integrate peak linear" button from the column of buttons directly above the plot of heat flow rate (watts / gram) as a function of temperature (degrees Celsius). Place two cursors on both the baseline to the left and right of the heat generation peak; select the nearest straight-line segment immediately to the left and right of the peak to place the cursors. Click "Enter" to perform the integration and calculation of the enthalpy generation, the peak maximum value of the enthalpy, and the heat enthalpy of the exotherm (joules / gram). Record all three values. Right-click on the end point of the heat generation signal by visually confirming the point where the signal first returns to the baseline, and click "Enter" to mark the end point in degrees Celsius. If there are multiple heat generation peaks, each heat generation must be integrated individually, and the total enthalpy of curing is the sum of the enthalpies of all heat generations. Print a hard copy of the thermogram plot of heat flow rate (W / g) versus temperature (°C) and create a PDF. Convert the x-axis to time units (minutes) and mark the occurrence and end of heat generation in time units using the same procedure as marking the end point of heat generation in temperature; print a hard copy of the thermogram plot of heat flow rate (W / g) versus time (minutes) and create a PDF. In the formal report, record the occurrence and peak maximum value of each heat generation peak rounded to the nearest integer degree Celsius to the first decimal place, and record the curing enthalpy rounded to the nearest integer joules / gram to the first decimal place. Do not forget to take the sum of the enthalpies for all existing heat generation peaks and record the total enthalpy of curing. Table 6 below summarizes the results of the DSC analysis.

[0060] [Table 6]

[0061] These results demonstrate that some embodiments of the present additive manufacturing composition have a rate of enthalpy change of less than 9.0 J / g-min, instead less than 8.0 J / g-min, instead less than 7.1 J / g-min.

[0062] Example 9 When thermosetting compositions cure, they tend to undergo shrinkage after expansion. The deformation is thought to be due to excessive shrinkage and / or excessive total shrinkage by the additive manufacturing composition during curing. As used herein, total shrinkage refers to the absolute difference between the maximum expansion point and the maximum shrinkage point (both as a percentage of the gap height of the test composition in the parallel plate rheometer procedure below). In this example, shrinkage and total shrinkage during curing are tested for some embodiments of the present additive manufacturing composition. The test procedure was performed using a parallel plate rheometer capable of acting under axial force control and having temperature control ability. The rheometer was equipped with plates of about 25 mm. Prior to performing the linear shrinkage test, some pre-test data for the composition, such as: (1) the gelation time, interval, and peak exotherm of the test composition from the total exotherm curve reaching at least 1 hour past the peak exotherm; (2) the strain sweep rheology of the test composition to identify the linear elastic response region; and (3) standard 3D printing rheology test data (at a flow rate of 50 seconds -1 is desirable.

[0063] The test procedure should be carried out with close cooperation between the chemist handling the start of the test and the analytical chemist starting the rheometer. The test procedure was performed as follows. 50 g of the test samples (Compositions A, B, D, F, G, H, I, P, Q, R, S, T and EXP-1593 of Example 6) were placed in a 250 mL beaker. The initiator in the amount specified in Table 6 was added. The timer was started and the sample was stirred with a metal spatula for 1 minute while carefully rubbing the sides and bottom of the container. The material was scraped off the spatula with a tongue depressor and returned to the container, and the sample was stirred again for 30 seconds in the same manner. The material was scraped off the spatula with a tongue depressor and returned to the container. The sample was applied to the rheometer plate and the rheometer was started using the following starting rheometer settings: (note that the rheometer start time is relative to the start time): Temperature: 30 °C; Gap target: 1 mm; Axial load control: Set to maintain on load; and 1 Hz vibration into the linear elastic region identified by strain sweep (preliminary test #2). The 1 Hz vibration was continued until the storage modulus reached 100 kPa or until three times the storage modulus reached the recovery period of the rheology test (preliminary test #3), or until the higher value was reached. This was designated as the gel point. The vibration was stopped and the temperature of the test sample was raised to the peak heat generation over the recorded interval time (from preliminary test #1). Next, the sample was cooled at a rate simulating the cooling curve (from preliminary test #1).

[0064] The data collected from this test includes shrinkage from the initial gap (referred to as "shrink") and the total gap change from maximum expansion to maximum shrinkage (referred to as "total shrink"). The results of this example are shown in Table 7 and Figure 6 below. Figure 6 is a graph of expansion and shrinkage measured from two batches of Composition A (MayBaseNKCDrum-1 and MayBaseNKCDrum-2). Each batch was tested both with degassing (to give a composition substantially void of gas voids) and without degassing (MayBaseNKCDrum-NoVac-1 and MayBaseNKCDrum-NoVac-2). The left axis of Figure 6 shows the percentage of change and the right axis shows temperature. Figure 6 illustrates that the test samples exhibit expansion between 7% and 9% as the temperature of the test samples rises from about 30°C to temperatures between 65°C and 70°C. As the temperature of the test samples decreased, the material shrank back to its initial gap height and continued to shrink, showing shrinkage between 3% and 6%.

[0065] [Table 7]

[0066] The results demonstrate that some embodiments of the present additive manufacturing compositions have a linear shrinkage of less than about 15.0%, instead less than about 14.0%.

[0067] Exemplary Embodiments To provide further assistance in understanding the present disclosure, the following exemplary embodiments are provided. Before describing the various embodiments, it should be understood that the teachings of the present disclosure are not limited to the specific embodiments described. Embodiment 1. An additive manufacturing composition comprising a thermosetting material comprising a crosslinkable component; and an initiator for free radical crosslinking, wherein when the composition is deposited in a series of layers, the composition cures without substantial deformation. Embodiment 2. The composition of Embodiment 1, which has a peak exothermic temperature of 50 °C or lower and / or a time to peak exotherm of less than 70 minutes during curing (e.g., when curing as a plurality of deposited layers). Alternatively or in addition, the composition has a peak exothermic temperature of less than 80 °C, 75 °C, 72 °C, 68 °C, 67 °C, or 65 °C during curing as a cylindrical mass. Embodiment 3. The composition of Embodiment 1 or Embodiment 2, which exhibits a peak exotherm that does not exceed 30 °C above the temperature at which the composition begins to cure, alternatively does not exceed 35 °C above, alternatively does not exceed 40 °C above when the composition is curing. In some embodiments, the composition during curing exhibits a peak exotherm that does not exceed 30 °C above the temperature at which the composition is deposited as a layer, alternatively does not exceed 35 °C above, alternatively does not exceed 40 °C above. Embodiment 4. The composition of any of the preceding embodiments, which has an enthalpy change rate of 9.0 J / g-min or less, alternatively 8.0 J / g-min or less, alternatively 7.1 J / g-min or less, alternatively 6.0 J / g-min or less. Embodiment 5. The composition of Embodiment 1, which is substantially void of gas voids before and / or during curing.

[0068] Embodiment 6. The composition of any of the preceding embodiments, wherein the crosslinkable component is a vinyl ester component or an unsaturated polyester component. Embodiment 7. The composition of any of the preceding embodiments, wherein the initiator comprises a peroxide selected from cumene hydroperoxide, benzoyl peroxide, or a blend of cumene hydroperoxide and methyl ethyl ketone peroxide. Embodiment 8. The composition of any of the preceding embodiments, which has a maximum linear shrinkage of less than about 9%, or less than about 8%, or less than about 7.1%. Alternatively or in addition, the composition has a maximum total shrinkage of less than about 15%, alternatively less than about 14%, alternatively less than 13%. Embodiment 9. An object prepared by curing an additive manufacturing composition of any of the preceding embodiments, the object comprising a plurality of layers. Embodiment 10. The object of Embodiment 9, wherein at least one of the layers has a length in the X direction and / or the Y direction of 1.0 m or more. Embodiment 11. The object of Embodiment 9 or Embodiment 10, wherein the object includes at least 10 layers.

[0069] Embodiment 12. A method for additive manufacturing of an object, including depositing a first layer of a thermosetting material on a support at a deposition temperature; and curing the first layer of the thermosetting material, wherein the peak exothermic temperature during curing is not more than 30°C higher than the deposition temperature, alternatively not more than 32°C or 35°C higher. In some embodiments, the thermosetting material is selected from any of Embodiments 1-8. Embodiment 13. The method of Embodiment 12, further including depositing a second layer of a thermosetting material on the first layer on the opposite side of the support, wherein the first layer undergoes an exothermic reaction and the first layer releases heat to the second layer. In some embodiments, the second layer of the thermosetting material is selected from any of Embodiments 1-8. Embodiment 14. The method of Embodiment 12, including depositing a third layer of a thermosetting material above the second layer and on the opposite side of the first layer and the support; curing the thermosetting material deposited as the third layer; and optionally depositing and curing additional layers until the desired height of the object is achieved. In some embodiments, the third layer of the thermosetting material is selected from any of Embodiments 1-8. Embodiment 15. The method of any of Embodiments 12-14, including applying a first series of layers, which have an average peak temperature (MPT) during curing; and depositing a second series of layers, wherein the MPT of the second series of layers is within 25°C of the MPT of the first series of layers. Embodiment 16. The method of Embodiment 15, wherein the first series of layers releases heat to the second series of layers. Embodiment 17. The method of any of Embodiments 12-16, wherein the deposition step includes depositing a thermosetting material to obtain a layer with a thickness of 1.27-12.7 mm. Embodiment 18. The method of any of Embodiments 12-17, wherein the curing of the thermosetting material is at atmospheric temperature or at a temperature of 20°C to 50°C. Embodiment 19. The method according to any one of Embodiments 12 to 18, wherein the curing of the thermosetting material is performed without applying secondary energy.

[0070] The above description explains and illustrates one or more specific embodiments. This description is not provided to limit the present disclosure to the embodiments described herein. Rather, it explains and teaches various principles so that those skilled in the art can understand these principles and, by such understanding, apply them not only to the embodiments described herein but also to other embodiments that may come to mind in accordance with these principles. The scope of the present disclosure is intended to cover all such embodiments that may fall within the scope of the appended claims, either literally or by the doctrine of equivalents. The present disclosure acknowledges that various embodiments, including at least the following claims, are disclosed herein.

Claims

1. the below described: A thermosetting material comprising a crosslinkable component; and Free Radical Crosslinking Initiators An additive manufacturing composition comprising: When the composition is deposited in a series of layers, the composition hardens without substantial deformation. The composition.

2. 10. The composition of claim 1, wherein the composition has a peak exotherm temperature of 50°C or less during curing as one or more deposited layers.

3. 10. The composition of claim 1, wherein as the composition cures, the composition exhibits a peak exotherm that is no more than 35°C higher than the temperature at which the composition begins to cure.

4. 10. The composition of claim 1, wherein the composition has an enthalpy change of 9 J / g-min or less.

5. The composition of claim 1 , wherein the composition is substantially free of gas voids before and / or during cure.

6. 2. The composition of claim 1, wherein the crosslinkable component is a vinyl ester component or an unsaturated polyester component.

7. 10. The composition of claim 1, wherein the initiator comprises a peroxide selected from cumene hydroperoxide, benzoyl peroxide, or a blend of cumene hydroperoxide and methyl ethyl ketone peroxide.

8. 10. The composition of claim 1, wherein the composition has a linear shrinkage of 6.0% or less.

9. 10. The composition of claim 1, wherein the composition has a total shrinkage of 15.0% or less.

10. 13. An object prepared by curing the additive manufacturing composition of claim 1, the object comprising multiple layers.

11. 11. The object of claim 10, wherein at least one of the layers has a length in the X and / or Y directions of 1.0 m or more.

12. The article of claim 11 , wherein the article comprises at least 10 layers.

13. 1. A method for additive manufacturing of an object, comprising: depositing a first layer of a thermosetting material onto a substrate at a deposition temperature; curing the first layer of thermosetting material. wherein the peak exotherm temperature during curing is not more than 35° C. higher than the deposition temperature; The method.

14. 14. The method of claim 13, further comprising depositing a second layer of a thermosetting material on the first layer on an opposite side of the support, during which the first layer undergoes an exothermic reaction and the first layer releases heat to the second layer.

15. In addition: depositing a third layer of a thermosetting material over said second layer and on a side opposite said first layer and said support; curing the thermosetting material deposited as the third layer; and optionally, depositing and curing additional layers until a desired height of said object is achieved.

14. The method of claim 13, comprising:

16. applying a first series of layers, the first series of layers having a mean peak temperature (MPT) during cure; 14. The method of claim 13, comprising depositing a second series of layers, the MPT of the second series of layers being within 25° C. of the MPT of the first series of layers.

17. The method of claim 16 , wherein the first series of layers releases heat to the second series of layers.

18. The method of claim 13, wherein the depositing step includes depositing the thermosetting material to obtain a layer having a thickness of between 1.27 and 12.7 mm.

19. The method of claim 13, wherein the curing of the thermosetting material is at ambient temperature or at a temperature between 20°C and 50°C.

20. The method of claim 13 , wherein curing of the thermosetting material occurs without the application of secondary energy.

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