Nucleation method for producing polycaprolactone powder

Abstract

A method for preparing polycaprolactone powders having properties that make them suitable for powder bed fusion 3D printing processes is disclosed. The polycaprolactone powders disclosed herein have a melting enthalpy between 80 J / g and 140 J / g. The polycaprolactone powders described herein have a D of between 20 micrometers and 150 micrometers. 90 The polycaprolactone powders described herein contain detectable amounts of a biocompatible solvent, a bioabsorbable solvent, and / or ethyl lactate.

Description

Description of Related Applications

[0001] This patent application claims priority to U.S. Provisional Patent Application No. 63 / 234812, filed August 19, 2021, and U.S. Provisional Patent Application No. 63 / 265641, filed December 17, 2021, which are incorporated herein by reference in their entireties. [Technical Field]

[0002] The present disclosure relates to the production of polycaprolactone (also referred to as PCL) powder. The disclosed polycaprolactone powder can be used as a build material for producing three-dimensional objects by 3D printing or other known manufacturing methods, such as molding. The disclosed polycaprolactone powder may be suitable for producing implantable objects by selective laser sintering (SLS). [Background technology]

[0003] Biocompatible and bioabsorbable polymers may be used to manufacture medical implants that are non-toxic to the human body.

[0004] 3D printers create solid three-dimensional objects by bonding adjacent materials together, for example, by melting and / or sintering them so that they solidify together upon cooling. 3D printers typically build objects layer by layer, following the instructions of a computer-aided design (CAD) model. 3D printing is a type of additive manufacturing. Additive manufacturing techniques may include material extrusion, powder bed fusion bonding, binder jetting, vapour photopolymerization, sheet lamination, directed energy deposition, and material jetting.

[0005] Selective laser sintering (SLS) is a type of 3D printing that can be used to create, among other things, medical implants. SLS machines may require the printing / build material to be in the form of a powder with a specific particle size distribution and other characteristics. The machine may also require the printing material to have a degree of flowability. Flowability allows the printing material to spread evenly and place each new layer of build material before applying electromagnetic energy (typically in the form of laser energy) to sinter predetermined areas.

[0006] 3D printing applications may include SLS (selective laser sintering), MJF (multi-jet fusion), HSS (high speed sintering), and electrophotography. Summary of the Invention [Problem to be solved by the invention]

[0007] To improve the flowability of SLS printing materials, flow aids are sometimes added. However, adding some flow aids to medical implants may be undesirable because the addition may cause adverse effects in the patient's body. Therefore, when producing SLS powders for producing medical implants, it may be desirable in some instances to have good particle sphericity to minimize or eliminate the need for flow aids. [Means for solving the problem]

[0008] The present disclosure relates to a solvent precipitation method for producing partially crystalline polycaprolactone powder that is compatible for use in SLS equipment.

[0009] Numerous variations within the scope of the claims will include processes, compositions, and articles of manufacture related to the preparation of PCL powder and its use in additive manufacturing processes, including PBF processes.

[0010] At least one variation will include a powder comprising polycaprolactone particles, wherein greater than 90 volume percent of the particles have a particle size between 20 and 150 micrometers. The powder has a detectable amount of solvent and a detectable amount of nucleating agent, wherein the solvent is a biocompatible or bioabsorbable solvent. In one variation, the solvent is ethyl lactate. In one variation, the nucleating agent is hydroxyapatite. In one variation, greater than 90 volume percent of the polycaprolactone particles have a sphericity greater than 0.75. In another variation, greater than 90 volume percent of the polycaprolactone particles have a sphericity greater than 0.80. In one variation, the volume percent of polycaprolactone particles having a particle size less than 20 micrometers is zero or undetectable. In one variation, the powder has a peak melting temperature of about 55°C to about 65°C and a melting enthalpy of about 90 J / g to about 120 J / g. In some variations, the powder has a recrystallization peak of about 15°C to about 35°C. In some variations, the powder has a decomposition temperature of about 250°C to about 425°C. In some variations, greater than 96 number percent of the polycaprolactone particles have a particle size less than 125 micrometers. In some variations, the polycaprolactone particles have a moisture content adjusted and maintained between 0.5% w / w and 5% w / w.

[0011] At least one variation may include a method for preparing PCL powder, which may include blending polycaprolactone in a polar organic solvent, dissolving the polycaprolactone in the polar organic solvent to form a solution, and cooling the solution to a temperature that precipitates at least a portion of the dissolved polycaprolactone. A nucleating agent may be added to the solution to promote precipitation. The powder is separated from the solution, leaving behind a second, more dilute PCL solution and contaminants from the starting PCL, such as residual catalyst, initiator, polymerization solvent, monomers, and oligomers. The separated powder may then be washed and dried. In some variations, the method further includes heating the combined polycaprolactone and polar organic solvent. In some variations, the method further includes a separation step of separating dried polycaprolactone particles having a particle size less than 150 micrometers from larger dried polycaprolactone particles to form sized polycaprolactone. In some variations, the percent of nucleating agent in the combined polycaprolactone / nucleating agent mixture is between about 0.5 and 10 weight percent. In some variations, the nucleating agent is hydroxyapatite. In some variations, the polar organic solvent is selected from the group consisting of ethyl acetate, ethyl lactate, γ-valerolactone, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dichloromethane (DCM), chloroform, acetone, and dimethyl sulfoxide (DMSO).

[0012] At least one variation may include a method for producing a powder comprising polycaprolactone particles, comprising combining polycaprolactone with a polar organic solvent and dissolving the polycaprolactone in the polar organic solvent along with at least one nucleating agent. The solution may then be cooled to a lower temperature that precipitates at least a portion of the dissolved polycaprolactone into the solution. The precipitated polycaprolactone is separated from the solution, washed, and dried. In some variations, the method includes heating the solution.

[0013] At least one variation may include an additive manufacturing method including selectively fusing or sintering adjacent polycaprolactone particles. More than 95 percent of the polycaprolactone particles have a particle size of less than 125 micrometers, and more than 90 percent by volume of the polycaprolactone particles have a sphericity greater than 0.75. The polycaprolactone particles contain a detectable amount of ethyl lactate and a detectable amount of hydroxyapatite. In one variation, the polycaprolactone particles have a moisture content adjusted and maintained between 0.5% w / w and 5% w / w.

[0014] At least one variation may include an article comprising polycaprolactone particles, wherein greater than 90 volume percent of the polycaprolactone particles have a particle size between 20 micrometers and 150 micrometers, wherein the polycaprolactone particles contain a detectable amount of a nucleating agent, and wherein the polycaprolactone particles contain a detectable amount of a solvent, the solvent comprising at least one of a biocompatible solvent or a bioabsorbable solvent.

[0015] At least one variation may include a medical article comprising polycaprolactone particles, wherein greater than 90 volume percent of the polycaprolactone particles have a particle size between 20 micrometers and 150 micrometers, wherein the polycaprolactone particles contain a detectable amount of a nucleating agent, and wherein the polycaprolactone particles contain a detectable amount of a solvent, including at least one of a biocompatible solvent or a bioabsorbable solvent.

[0016] Powder compositions for use in PBF processes are provided that include PCL powders prepared by such methods. Objects can be prepared by using such PCL powders in a PBF process to form the objects.

[0017] The disclosed examples of the apparatus, system, and method variations provide PCL powders with properties and characteristics suitable for use in SLS, MJF, HSS, and electrophotographic 3D printing applications. Embodiments of the present disclosure provide precipitated PCL powders formed by precipitating a polymer from a solvent, and the precipitated powdered polymer can then be utilized in powder-based 3D printing processes.

[0018] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure or the claims.

[0019] Variations may include a powder comprising polycaprolactone particles. In at least one variation, greater than 90 volume percent of the polycaprolactone particles have a particle size between 20 and 150 micrometers. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a flow chart illustrating a method for producing polycaprolactone powder according to at least one variation. [Figure 2] Graph showing results from thermogravimetric analysis (TGA) performed on samples of polycaprolactone produced according to at least one variation. [Figure 3] Graph showing differential scanning calorimetry (DSC) curves of polycaprolactone precipitated with at least one variation [Figure 4] Graph showing particle size volume distribution for SLS grade powders produced according to at least one variation. [Figure 5] Graph showing particle size number distribution for SLS grade powders produced according to at least one variation. [Figure 6] Table showing powder data for polycaprolactone powders produced according to at least one variation [Figure 7]Photographs of SLS printed bars using polycaprolactone containing 4% w / w (mass / mass) hydroxyapatite (also referred to as HA) in at least one variation. [Figure 8A] Graph showing tensile plots generated by pulling SLS-prepared polycaprolactone (containing 4% w / w hydroxyapatite) tensile bars. [Figure 8B] Table showing a summary of material properties obtained from tensile tests in FIG. 8A. [Figure 9] Graph showing DSC curves of resultant polycaprolactone powders nucleated with hydroxyapatite according to at least one variation. [Figure 10] a graph showing particle number size distribution according to at least one variation; [Figure 11] a graph showing particle number size distribution according to at least one variation; [Figure 12A] FIG. 1 shows polycaprolactone powder nucleated with 4% w / w hydroxyapatite according to at least one variation. [Figure 12B] FIG. 1 shows polycaprolactone powder dry blended with 4% w / w hydroxyapatite according to at least one variation and allowed to stand for 24 hours. [Figure 13] Table showing a comparison of particle size distribution between polycaprolactone precipitated neat and polycaprolactone precipitated with hydroxyapatite acting as a nucleating agent, according to at least one variation. [Figure 14A] FIG. 1 shows a polycaprolactone pack prepared by a method according to at least one variation. [Figure 14B] FIG. 1 shows a polycaprolactone pack prepared by a method according to at least one variation. [Figure 14C] FIG. 1 shows a polycaprolactone pack prepared by a method according to at least one variation. [Figure 14D]FIG. 1 shows a polycaprolactone pack prepared by a method according to at least one variation. [Figure 14E] FIG. 1 shows a polycaprolactone pack prepared by a method according to at least one variation. [Figure 14F] FIG. 1 shows a polycaprolactone pack prepared by a method according to at least one variation. [Figure 14G] FIG. 1 shows a polycaprolactone pack prepared by a method according to at least one variation. [Figure 15] Graph showing DSC curves of polycaprolactone powder reprecipitated in ethyl lactate according to at least one variation. [Figure 16] Graph showing DSC curves of polycaprolactone powder reprecipitated in the presence of 4% w / w hydroxyapatite as a nucleating agent, according to at least one variation. DETAILED DESCRIPTION OF THE INVENTION

[0021] The following description is merely illustrative in nature of the subject matter, manufacture, and use of one or more inventions and is not intended to limit the scope, application, or use of any particular invention claimed in this application or any other application claiming priority to this application, or any patent issued therefrom. With respect to the disclosed methods, the order of steps presented is exemplary in nature; therefore, the order of steps may vary in various embodiments. As used herein, nouns indicate that there is "at least one" of the object, and, where possible, that there may be more than one of such object. Unless otherwise specified, in describing the broadest scope of the technology, all numerical quantities in this description should be understood to be modified by the word "about," and all geometric and spatial descriptors should be understood to be modified by the word "substantially." When applied to a numerical value, "about" indicates that the value may be calculated or measured with some degree of slight imprecision (e.g., a certain approach to precision in the value; approximately or reasonably close to the value; almost). If for any reason the imprecision imparted by "about" and / or "substantially" is not understood according to its ordinary meaning in the art, then "about" and / or "substantially" as used herein will account for at least the variation that might result from ordinary methods of measuring or using such parameters.

[0022] Although the open-ended term "comprising" is used herein as a synonym for non-limiting terms such as include, contain, or have to describe and claim embodiments of the present invention, embodiments may instead be described using more restrictive terms such as "consisting of" or "consisting essentially of." Thus, for any given embodiment describing a material, component, or process step, the present technology also specifically includes embodiments that consist of, or consist essentially of, such material, component, or process step, excluding (to consist of) the additional material, component, or process, even if such additional material, component, or process is not expressly described in this application, and excluding (to consist essentially of) any additional material, component, or process that affects a critical characteristic of the embodiment. For example, a description of a composition or process reciting elements A, B, and C specifically contemplates embodiments consisting of, and consisting essentially of, A, B, and C, excluding element D, as may be described in the art, even though element D is not expressly described herein as excluded.

[0023] The term "or" as used herein in connection with a list of two or more items, elements, components, or materials does not indicate a complete disjunction, such that the listed items, elements, components, or materials are mutually exclusive. For example, "X, Y, or Z" does not mean that each of X, Y, and Z is mutually exclusive. Two or more of X, Y, and Z may partially or completely overlap with each other, or at least one of X, Y, or Z may be included in, or be a subgenus of, at least one of another of X, Y, or Z. As another example, "cells may be grown in a monolayer, three-dimensionally, or on beads" does not mean that cells grown on beads do not include cells grown in three dimensions. As a further example, "at least one of a biocompatible solvent; a bioresorbable solvent, or ethyl lactate" does not mean that neither ethyl lactate nor a solvent comprising ethyl lactate is a biocompatible solvent or a bioresorbable solvent, or that a biocompatible solvent or a bioresorbable solvent cannot be or comprise ethyl lactate.

[0024] As referred to herein, the disclosure of ranges includes endpoints, unless otherwise specified, and includes all individual values ​​and further divided ranges within the entire range. Thus, for example, a range of "from A to B" or "from about A to about B" includes A and B. The disclosure of a value and range of values ​​for a particular parameter (amount, mass percent, etc.) does not exclude other values ​​and ranges of values ​​useful herein. It is contemplated that two or more specific exemplary values ​​for a given parameter may define the endpoints of a range of values ​​that may be claimed for that parameter. For example, if parameter X is exemplified herein as having a value A and also exemplified as having a value Z, then parameter X is contemplated to have a range of values ​​from about A to about Z. Similarly, the disclosure of two or more ranges of values ​​for a parameter (whether such ranges are nested, overlapping, or separate) is contemplated to encompass all possible combinations of value ranges that may be claimed using the endpoints of the disclosed ranges. For example, if a parameter X is exemplified herein as having a value in the range of 1 to 10, or 2 to 9, or 3 to 8, it is contemplated that the parameter X may have other ranges of values, including 1 to 9, 1 to 8, 1 to 3, 1 to 2, 2 to 10, 2 to 8, 2 to 3, 3 to 10, 3 to 9, etc.

[0025] When an element or layer is referred to as "on," "engaged with," "connected to," or "coupled to" another element or layer, it may be directly on, engaged with, connected to, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element or layer is referred to as "directly on," "directly engaged with," "directly connected to," or "directly coupled to" another element or layer, there will be no intervening elements or layers. Other words used to describe relationships between elements should be interpreted similarly (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0026] Terms such as "first," "second," and "third" may be used herein to describe various elements, components, regions, layers, and / or sections; however, these elements, components, regions, layers, and / or sections are not intended to be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or section from another region, layer, or section. Terms such as "first," "second," and other numerical terms, when used herein, do not imply any order or sequence unless clearly indicated by context. Thus, a first element, component, region, layer, or section described below could be referred to as a second element, component, region, layer, or section without departing from the teachings of the illustrative embodiments.

[0027] Spatially relative terms such as "inside," "outside," "below," "below," "downward," "above," and the like may be used herein for ease of description to describe the relationship of an element or feature to other elements or features, as shown in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures were turned over, elements described as "below" or "below" other elements or features would then be oriented "above" the other elements or features. Thus, the illustrative term "below" may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0028] The particle size of the PCL polymer can affect its use in additive manufacturing processes. As used herein, D 50 (also known as the "volume median diameter" or "mean particle size by volume") refers to the particle size of a powder at which 50% by volume of the particles in the total distribution of a reference sample have a particle size equal to or less than the stated particle size. 10 refers to the particle size of a powder at which 10% by volume of the particles in the total distribution of the reference sample have a particle size less than or equal to the stated particle size, and D90 refers to the particle size of a powder at which 90% by volume of the particles in the total distribution of a reference sample have a particle size equal to or less than the stated particle size. Particle size may be measured by any suitable method known in the art for measuring particle size in diameter. The semi-crystalline polymer powders provided herein have a diameter of less than 150 μm. 90 It may have a particle size.

[0029] As used herein, "layer" is a convenient term that refers to any shape, regular or irregular, having at least a predetermined thickness. In certain embodiments, the size and contour of two dimensions are predetermined, and in certain embodiments, the size and shape of all three dimensions of the layer are predetermined. The thickness of each layer can vary widely depending on the additive manufacturing method. In certain embodiments, the thickness of each as-formed layer can be different from previous or subsequent layers. In certain embodiments, the thickness of each layer can be the same. In certain embodiments, the thickness of each as-formed layer can be between 0.5 millimeters (mm) and 5 mm.

[0030] Certain variations may include forming multiple layers in a predetermined pattern in an additive manufacturing process. In many variations, additive manufacturing may produce two or more layers, or even 20 or more layers. The maximum number of layers may vary significantly and may depend on considerations such as the size of the object being manufactured, the technology used, the production volume and capabilities of the equipment used, and the level of detail desired in the final object. For example, 5 to 100,000 layers may be formed, or 20 to 50,000 layers may be formed, or 50 to 50,000 layers may be formed.

[0031] The term "powder bed fusing" or "powder bed fusion" is used herein to mean a process in which polymers are selectively sintered or melted and fusion-bonded layer by layer to provide a 3D object. Sintering may result in an object having a density less than about 90% of the density of the solid powder composition, whereas melting may provide an object having a density between 90% and 100% of the density of the solid powder composition. The use of semi-crystalline polymers as provided herein may facilitate melting such that the resulting density approaches that achieved by injection molding processes.

[0032] Powder bed fusion further includes all laser sintering processes and all selective laser sintering processes, as well as other powder bed fusion techniques defined by ASTM F2792-12a. For example, sintering of a powder composition can be achieved by the application of electromagnetic radiation other than that produced by a laser, with selectivity of sintering being achieved, for example, by the use of inhibitors, absorbers, susceptors, or the selective application of electromagnetic radiation (e.g., the use of a mask or a directed laser beam). Any other suitable electromagnetic radiation source may be used, including, for example, an infrared radiation source, a microwave generator, a laser, a radiant heater, a lamp, or a combination thereof. In certain embodiments, selective mask sintering ("SMS") techniques may be used to fabricate three-dimensional objects. For further discussion of the SMS process, see, for example, U.S. Patent No. 6,531,086, the entire contents of which are incorporated herein by reference, which describes an SMS apparatus in which a shielding mask is used to selectively block infrared radiation and result in selective irradiation of portions of the powder layer. When using an SMS process to fabricate an object from a powder composition of the present technology, it may be desirable to include in the powder composition one or more materials that enhance the infrared absorption properties of the powder composition. For example, the powder composition may include one or more heat sinks (e.g., glass fiber or glass microbeads) or dark materials (e.g., carbon black, carbon nanotubes, or carbon fiber).

[0033] Also included herein are any three-dimensional objects fabricated by powder bed fusion bonding compositions containing the semicrystalline polymer powders described herein. After layer-by-layer fabrication of the object, the object may exhibit excellent resolution, durability, and strength. Such objects may include a variety of manufactured articles with a wide variety of uses, including as prototypes, final products, and molds for final products.

[0034] The object may be formed from a predetermined pattern, which may be determined from a three-dimensional digital representation of the desired object as known in the art or as described herein. Materials may be bonded or solidified under computer control, for example, by computer-aided design (CAD) operations, to create the three-dimensional object.

[0035] Specifically, powder bed fusion-bonded (e.g., laser sintered) objects may be fabricated from compositions containing PCL powder using any suitable powder bed fusion process, including laser sintering processes. These objects may, in some embodiments, comprise multiple overlapping, adhesively sintered layers comprising a polymer matrix, which may have reinforcing particles dispersed throughout the polymer matrix. Laser sintering processes are known, which are based on selective sintering of polymer particles, in which layers of polymer particles are briefly exposed to laser energy, and the polymer particles exposed to the laser energy are thus bonded to one another. Three-dimensional objects are fabricated by sequential sintering of layers of polymer particles. Details regarding selective laser sintering processes can be found, by way of example, in U.S. Pat. No. 6,136,948 and WO 96 / 06881, the entire contents of each of which are incorporated herein by reference. However, the semi-crystalline polymer powders described herein may also be used in other rapid prototyping or rapid manufacturing processes of the prior art, particularly those described above. For example, semi-crystalline polymer powders may be used to manufacture molds from the powder by, inter alia, the SLS (selective laser sintering) process, as described in U.S. Pat. No. 6,136,948 or WO 96 / 06881, by the SIB process (selective inhibition of powder bonding), as described in WO 01 / 38061, by 3D printing, as described in EP 0 431 924, or by a microwave process, as described in DE 10 311 438. The entire contents of each of these patent documents are incorporated herein by reference.

[0036] The fused layers of the powder bed fusion object can be of any thickness suitable for selective laser sintering processing. Each individual layer can be at least 50 μm thick, at least 80 μm thick, or at least 100 μm thick, on average. In numerous variations, each of the multiple sintered layers is less than 500 μm thick, less than 300 μm thick, or less than 200 μm thick, on average. Thus, individual layers for some embodiments can be 50 to 500 μm, 80 to 300 μm, or 100 to 200 μm thick. Three-dimensional objects fabricated from the powder compositions of the present technology using layer-by-layer powder bed fusion processes other than selective laser sintering can have layer thicknesses the same as or different from those described above.

[0037] Numerous variations provide methods for producing and using PCL powders with characteristics suitable for use in selective laser sintering (SLS), multi-jet fusion (MJF), high-speed sintering (HSS), and electrophotographic (EPG) 3D printing. At least one variation provides precipitated PCL powder formed by precipitation of a polymer from a saturated solution of PCL in a polar organic solvent, allowing the polymer to form crystallites, and then utilizing the precipitated polymer powder in a PBF 3D printing process. Many PCL powder variations may exhibit characteristics optimized for the PBF process, including optimized particle size, dispersion, shape, and crystallinity, while also using a single-solvent process without the use of dispersants for their production.

[0038] The method for preparing PCL powder involves dissolving bulk PCL in ethyl lactate to form a solution at elevated temperature; cooling the solution to room temperature to form a powder with a D of less than 150 micrometers (microns, or μm). 90 value, D below 100 μm 50 value, or D from 0 to 100 μm 50This method may also include forming a PCL powder as a precipitate having a desired value. This method may also result in a product in which the particles exhibit a specific size (average diameter of about 30 μm to about 40 μm), low dispersity, spheroidal shape, and crystalline characteristics suitable for the printing process described above compared to the results of the process described above. The reprecipitation process also serves to purify the PCL.

[0039] Powder compositions for use in PBF processes are provided that include PCL powders prepared by such methods. Objects can be prepared by using such PCL powders in a PBF process to form the objects.

[0040] In certain embodiments, a method for preparing PCL powder is provided, comprising dissolving bulk PCL in a polar solvent, such as an ester (e.g., ethyl lactate), to form a first solution of molten polymer at a first temperature. This first solution is then cooled to a second temperature lower than the first temperature. A portion of the molten PCL precipitates as a powder from the first solution, either en route to or upon reaching the second temperature, leaving behind a second, more dilute PCL solution. The precipitated PCL powder may be separated from the remainder of the second solution, for example, by gravity filtration, vacuum filtration, or centrifugation. The separated PCL powder may be washed with water or an organic solvent, provided that the washing solvent is miscible with the solvent used for reprecipitation, does not dissolve the polymer powder to a detrimental extent (e.g., unacceptable excessive material loss and / or unacceptable excessive particle size reduction), and will not be a solvent for the polymer powder product at all. The separated PCL powder, if applied, may be dried after any washing procedures. In certain embodiments, the polar solvent will include ethyl lactate. In other embodiments, the polar solvent may consist essentially of ethyl lactate. In yet further embodiments, the polar solvent may consist of ethyl lactate.

[0041] A variety of solvent temperatures may be utilized in the method of preparing PCL powder by reprecipitation. The dissolving step may include heating PCL in a polar solvent to form a first solution of dissolved PCL at a first temperature above room temperature. The cooling step may include cooling the first solution to a second temperature, which may be below the precipitation temperature of the polymer solution and at or below ambient temperature ("room temperature"). Ambient ("room") temperature is understood to be approximately 20-25°C (68-77°F).

[0042] Various embodiments of PCL may exhibit the following physical characteristics: The PCL powder has a D of less than about 150 μm. 90 In certain embodiments, the PCL powder may have a particle size of less than about 100 μm. 50 The PCL powder may have a D of about 1 micrometer to about 100 μm. 50 Certain embodiments may have a D value of about 30 μm to about 40 μm. 50 The PCL powder may be in the form of spheroidal particles.

[0043] The melting point and enthalpy of fusion of the polymer powder may be determined using differential scanning calorimetry (DSC); for example, a TA Instruments Discovery Series DSC 250 scanned at 20° C. / min.

[0044] The percent crystallinity of a polymer is sometimes determined by the ratio of the enthalpy of fusion measured by DSC to the enthalpy of fusion of a theoretical 100% crystalline polymer, which for PCL has been reported to have a value of 139.5 J / g (Gupta and Geeta, J. Appl. Polym.. Sci. 2012, 123(4), 1944-1950). Percent crystallinity can also be determined directly by powder X-ray crystallography and correlated to the enthalpy of fusion in a direct linear relationship.

[0045] The powder flow of polymer powders may be measured using Method A of ASTM D1895 and was determined using a cone with a nozzle diameter of 10 mm.

[0046] In some embodiments, the particle size of the polymer powder is determined by laser diffraction, as known in the art. For example, the particle size can be determined using a laser diffractometer such as a Microtrac S3500.

[0047] In certain embodiments, powder compositions for use in PBF 3D printing processes are provided, wherein such powder compositions comprise PCL powder prepared according to the methods provided herein. For example, powder compositions for use in PBF processes may comprise a PCL powder having a D of less than about 150 μm. 90 particle size, and D of about 30 μm to about 40 μm 50 Such powder compositions may include PCL powders having different physical characteristics as well as mixtures of additives and other ingredients as described herein.

[0048] In certain embodiments, the reprecipitated PCL powder prepared by the methods disclosed herein is used in a PBF 3D printing process to form an object. Certain methods for preparing objects include those having a D of less than about 150 μm. 90 particle size, and D of about 30 μm to about 40 μm 50 The method includes providing a PCL powder having a value, which is then used in a PBF process to form an object.

[0049] In certain embodiments, one or more objects are provided that are prepared by an additive manufacturing process. Such methods may include providing a PCL powder prepared by one or more of the methods described herein. The PCL powder is then used in a PBF process to form one or more objects.

[0050] Certain embodiments may include methods for powder bed fusion using a powder composition including PCL powder to form a three-dimensional object. Due to the good flowability of the reprecipitated PCL powder, a smooth and dense powder bed can be formed, optimizing the precision and density of the sintered object.

[0051] In certain embodiments, a method for preparing PCL powder includes dissolving bulk PCL in a polar solvent, such as ethyl lactate, at a temperature above room temperature. Ambient ("room") temperature is understood to be approximately 20-25°C (68-77°F), and thus, PCL may be dissolved in ethyl lactate at temperatures above ambient temperature. PCL is soluble in the ethyl lactate solvent, and therefore, a PCL solution is formed. Generally, the solution may be prepared at a temperature above room temperature so that the amount of dissolved PCL is greater than the amount that can maintain it in solution at ambient temperature. Mixing of PCL into the ethyl lactate solvent may be performed in-line or batchwise. The process may be easily carried out on a manufacturing scale. Upon cooling to room temperature (e.g., about 20°C), the dissolved PCL begins to crystallize and precipitate from the ethyl lactate solvent, forming a PCL precipitate.

[0052] After precipitation, the ethyl lactate solvent is removed, for example, by filtration or centrifugation. The PCL powder may then be washed with a solvent that is miscible with the reprecipitation solvent and reasonably volatile, such as water, filtered to remove the washing solvent, and dried with or without the application of heat or vacuum. It is more convenient to use a washing solvent in which PCL is minimally soluble or insoluble.

[0053] As described herein, PCL is dissolved in a polar organic solvent. For example, PCL may be dissolved in a solvent under conditions that result in a saturated solution of PCL, from which PCL powder precipitates by changing the conditions (e.g., lowering the temperature of the solution). In certain embodiments, the solvent may contain ethyl lactate as well as one or more other esters or one or more other polar organic solvents. In certain embodiments, the solvent may consist essentially of ethyl lactate, where no other components that substantially affect the crystallization of PCL are present. In certain embodiments, the solvent may be substantially 100% ethyl lactate. It is further noted that when precipitating PCL powder from a solution of PCL in ethyl lactate, some dissolved PCL may remain in solution. In certain embodiments, a secondary solvent that is miscible with the reprecipitation solvent but does not support the dissolution of PCL may be added to the PCL / solvent solution to induce precipitation. In certain embodiments, the use of a nucleating agent in powder form may induce precipitation, may help control particle size and particle size dispersity, and may help improve the overall spheroidal shape of the powder particles. Thus, upon separation of the precipitated PCL powder from the remainder of the solution, a solution of ethyl lactate containing some dissolved PCL remains.

[0054] Ethyl lactate is a useful solvent for the process in that it dissolves PCL well; it has been shown herein to produce a powder with characteristics suitable for the PBF 3D printing process; it has a boiling point far enough away from ambient temperature to allow for a wide cooling range during precipitation; it is miscible with commonly available effective cleaning solvents (e.g., water or low molecular weight alcohols); it has been shown to be relatively non-toxic in mammals (its use as a food additive has been demonstrated); and it can be degraded in the body to form ethanol and lactic acid.

[0055] In certain embodiments, the precipitated PCL powder has a D of less than 150 μm. 85 Particle size, especially D less than 150 μm 90 Certain embodiments provide that the PCL powder has a particle size D of less than 150 μm. 90PCL powders having a particle size of 100% less than 150 μm may also be produced by this method. 50 In particular, PCL powders may have a D value of 10 μm to 100 μm. 50 The average particle size of the PCL powder may be 100 μm or less, or may have a D value between 0 and 100 μm. 50 It may contain a value.

[0056] In certain embodiments, a method of preparing an article includes providing a powder composition comprising PCL powder and forming a three-dimensional object using a powder bed fusion process on the powder composition. The at least one PCL powder comprises particles having a diameter D of less than 150 μm. 50 The particles may have a particle size of less than 150 μm and are produced by the methods described above. 90 Particle size: 100 μm or less D 50 value, or D from 0 to 100 μm 50 Includes those that have values.

[0057] PCL powder may be used as the only component in a powder composition and applied directly to the powder bed fusion process. Alternatively, PCL powder may be first mixed with other polymer powders, such as another crystalline or amorphous polymer, or a combination of a semi-crystalline and an amorphous polymer. The powder composition used for powder bed fusion bonding may contain 50% to 100% by weight of PCL powder, based on the total weight of all polymeric materials in the powder composition.

[0058] The PCL powder may be combined with one or more additives / ingredients to create a powder useful in powder bed fusion processes. Such optional ingredients may be present in an amount sufficient to perform a specific function without adversely affecting the performance of the powder composition in powder bed fusion or an object prepared therefrom. The optional ingredients may have a D particle size that falls within the average particle size range of the PCL powder or optional flow agent. 50The optional components may have a value of 0.01 to 30% by weight. If necessary, each optional component may be milled to a desired particle size and / or particle size distribution, which may be substantially similar to the PCL powder. The optional components may be particulate materials and may include organic and inorganic materials, such as fillers, flow agents, and colorants. Additional optional components may include, for example, toners, extenders, fillers, colorants (e.g., pigments and dyes), lubricants, anticorrosive agents, thixotropic agents, dispersants, antioxidants, adhesion promoters, light stabilizers, organic solvents, surfactants, flame retardants, antistatic agents, plasticizers, and combinations comprising at least one of the foregoing. Yet another optional component may be a second polymer that alters the properties of the PCL powder. In certain embodiments, each optional component, if present at all, may be present in the powder composition in an amount of 0.01% to 30% by weight, based on the total weight of the powder composition. The total amount of all optional components in the powder composition can range from greater than 0% to 30% by weight, based on the total weight of the powder composition. Such additives can also improve the conversion of IR laser energy to thermal energy in the powder bed.

[0059] It is not necessary for each optional component to melt during a powder bed fusion process, such as a laser sintering process. However, each optional component may be selected to be homogeneously compatible with the PCL polymer to form a strong, durable object. An optional component may be, for example, a reinforcing agent that provides additional strength to the formed object. Examples of reinforcing agents include one or more of glass fiber, carbon fiber, talc, clay, wollastonite, glass beads, and combinations thereof. Such additives may also improve the conversion of IR laser energy to thermal energy in the powder bed.

[0060] The powder composition may optionally contain a flow agent. Specifically, the powder composition may contain a particulate flow agent in an amount of 0.01% to 5% by weight, particularly 0.05% to 1% by weight, based on the total weight of the powder composition. In certain embodiments, the powder composition contains a particulate flow agent in an amount of 0.1% to 0.25% by weight, based on the total weight of the powder composition. The flow agent contained in the powder composition may be a particulate inorganic material having a median particle size of 10 μm or less, and may be selected from the group consisting of hydrated silica, amorphous alumina, vitreous silica, vitreous phosphate, vitreous borate, vitreous oxide, titania, talc, mica, fumed silica, kaolin, attapulgite, calcium silicate, alumina, magnesium silicate, and combinations thereof. The flow agent may be present in an amount sufficient to allow the semi-crystalline polymer powder to flow and flatten onto the build surface of a powder bed fusion apparatus (e.g., a laser sintering apparatus). Such an additive may also improve the conversion of IR laser energy to thermal energy in the powder bed.

[0061] The powder composition may optionally contain an IR absorber to facilitate the conversion of laser energy to thermal energy in the SLS process. IR absorbers include metal oxides (e.g., titania, silica, glass, tungsten(VI) oxide), metal nanoparticles (e.g., gold nanorods), or IR absorbers that are irradiated at wavelengths of IR lasers (typically 943 cm-1). -1 It may be one or more of a variety of inorganic or organic substances, such as organic compounds that absorb strongly at wavelengths of 10.6 μm (corresponding to 10.6 μm).

[0062] Another optional component is a colorant, such as a pigment or dye, that imparts the desired color to the object. The colorant is not limited, as long as it does not adversely affect the composition or the object prepared therefrom, and the colorant is sufficiently stable to maintain its color under the conditions of the powder bed fusion process and under exposure to heat and / or electromagnetic radiation, such as the laser used in the sintering process. Such additives may also improve the conversion of IR laser energy to thermal energy in the powder bed.

[0063] Further examples of additives include toners, extenders, fillers, lubricants, anti-corrosion agents, thixotropic agents, dispersants, antioxidants, adhesion promoters, light stabilizers, organic solvents, surfactants, flame retardants, antistatic agents, plasticizers, and combinations thereof. Such additives may also improve the conversion of IR laser energy to thermal energy in the powder bed.

[0064] Yet another optional ingredient may be a second polymer that alters the properties of the PCL powder.

[0065] The powder composition is a fusible powder composition and may be used in a powder bed fusion process, such as selective laser sintering. An example of a selective laser sintering system for producing parts from a fusible powder composition, particularly from the fusible PCL powder disclosed herein, can be described as follows: A thin layer of a powder composition containing PCL powder is spread onto a sintering chamber. A laser beam traces a computer-controlled pattern corresponding to a cross-sectional section of a CAD model, selectively melting the powder, which has been preheated slightly below its melting temperature. After one layer of powder is sintered, the powder bed piston is lowered a predetermined increment (typically 100 μm), and another layer of powder is spread by a roller onto the previously sintered layer. This process is then repeated, with the laser melting each successive layer and fusion-bonding it to the previous layer until the entire object is completed. In this manner, the PCL powder described herein can be used to produce three-dimensional objects made from multiple fusion-bonded layers.

[0066] One or more variations may be configured and arranged to provide one or more advantages, which may include, but are not limited to, the use of a single solvent in the preparation of the PCL powder, which facilitates solvent recovery and reuse. In numerous variations, the PCL powder produced by at least one of the disclosed methods provides improved PBF performance. Accordingly, additive manufacturing processes utilizing powder bed fusion bonding, including selective laser sintering (SLS), multi-jet fusion (MJF), high-speed sintering (HSS), and electrophotographic 3D printing, would benefit from forming and using the PCL powder produced as described herein. In particular, 3D printing of implantable bioresorbable medical devices would benefit from the PCL powder materials described herein.

[0067] In many variations, the reprecipitation process can serve to purify the PCL material, removing residual catalyst, initiator, monomer, and other contaminants. By dissolving the PCL, contaminants trapped in interstitial spaces in the solid are released into the resulting PCL solution. When the PCL precipitates, the amount of contaminants reintroduced into the solid is significantly less, both due to the low likelihood of entrapment and the nature of crystallite formation, which eliminates the contaminants. The reprecipitation process may be repeated with fresh, uncontaminated solvent to further reduce the level of contaminants. A common contaminant to remove from PCL is tin compounds remaining from the common use of tin catalysts in the polymerization of ε-caprolactone.

[0068] Numerous variations may include a method of producing a powder suitable for additive manufacturing, the method comprising the steps of combining a suitable polymeric material and a solvent; dissolving the polymeric material suitable for additive manufacturing in the solvent to form a solution; cooling the solution to a temperature at which at least a portion of the dissolved polymeric material suitable for additive manufacturing precipitates from the solution; separating the precipitated polymeric material from the solution; washing the separated precipitated polymeric material to form a washed polymeric material; and drying the washed polymeric material to form a dried polymeric material suitable for additive manufacturing.

[0069] In at least one variation, the polycaprolactone powder may be formed by dissolving polycaprolactone in a heated solvent. Alternatively, the solvent may not require heating. The solvent may be a non-toxic, biocompatible solvent. In at least one variation, the solvent may be ethyl lactate. A single solvent may be used. A reprecipitation solvent may be used, such as gamma valerolactone and ethyl acetate. A reprecipitation system may be used, such as xylene and petroleum ether, tetrahydrofuran and methanol, or dichloromethane and water. In certain variations, a dispersing agent, such as polyvinylpyrrolidone, may also be utilized. [Example]

[0070] Reprecipitation of polycaprolactone powder FIG. 1 illustrates a method for producing polycaprolactone powder according to at least one variation. Polycaprolactone and a solvent are combined, for example, as shown in step 101. Polycaprolactone pieces of any size may be used. The solvent may be one or more of the solvents described above. A single solvent may be used. The polycaprolactone may be heated before being added to the solvent to prevent a drop in the temperature of the solvent upon addition of the polycaprolactone. The solvent may be heated. Optionally, the solvent may not require heating. In at least one variation, the polycaprolactone may be heated above the melting point of the polycaprolactone and then added to the solvent. The solvent may also have a temperature above the melting point of the polycaprolactone. The polycaprolactone / solvent combination may be mixed, for example, by stirring. A stirring speed of 200 to 800 revolutions per minute may be used. In at least one variation, a stirring speed of 600 to 700 rpm may be used. The polycaprolactone concentration can range from 1% w / v to 20% w / v, where the polycaprolactone concentration is calculated by dividing the mass of polycaprolactone (grams, g) by the volume of solvent (milliliters, ml). In some variations, the polycaprolactone concentration can be (a) 13% w / v to 15% w / v, or (b) 8% w / v to 10% w / v. Fresh or recycled solvent (previously used to reprecipitate polycaprolactone) can be used. In step 102, the temperature of the solvent / polycaprolactone mixture can be controlled to a set temperature. In one variation, the set temperature can be between 60°C and 145°C (inclusive). In at least one variation, the set temperature can range from 80°C to 110°C (inclusive). The set temperature can be very close (e.g., within about 5°C) to the melting point of the solvent. The boiling point of the ethyl lactate solvent may be about 154° C. The temperature of the solvent may be equal to the set temperature. The polycaprolactone may be dissolved in the solvent to form a solution, as shown in step 102.Step 102 may continue until all of the polycaprolactone has dissolved, at which point the solution will appear completely clear and there will be minimal or no visible solids.

[0071] In step 103, the temperature of the polycaprolactone solution may be reduced. The cooling step may reduce the temperature through and below the saturation point of the solution, which may cause the dissolved polycaprolactone to precipitate from the solution. In one variation, the temperature of the polycaprolactone / solvent solution may be reduced to room temperature. In step 104, the precipitated polycaprolactone may be separated from the solution. Separation may be performed, for example, by vacuum filtration or other separation techniques such as sieving, centrifugation, cyclone separators, air classification, drying, etc. After the polycaprolactone is separated from the solution in step 104, it may be washed in a washing step 105. A miscible washing liquid, such as water, may be used to displace and / or extract residual solvent from the polycaprolactone. The washing liquid may be combined with the polycaprolactone, and the mixture may be agitated. Alternatively, the wash liquid may be sprayed onto polycaprolactone solids arranged on a mesh or screen to displace and / or extract the solvent and wash it from the polycaprolactone. Other liquid displacement or extraction methods may also be used in step 105. After the polycaprolactone has been washed, it may be dried. The polycaprolactone may be dried by heating to a temperature ranging from ambient temperature (e.g., 20°C) to 50°C. The polycaprolactone may be stationary as hot air (or other gas, such as nitrogen) passes over it to carry away water vapor. Alternatively, the polycaprolactone may be placed in a rotating drum or otherwise moved during the drying process to improve mass transfer of the wash liquid from the polycaprolactone to the ambient environment. A vacuum system may be used to reduce the pressure to which the polycaprolactone is exposed during the drying process, reducing the energy required for drying and / or providing more thorough drying.

[0072] The dried polycaprolactone particles may be separated by size in step 107. Size separation can separate / isolate polycaprolactone particles having particle sizes within a range of 30 to 150 μm, 20 to 150 μm, or 1 to 150 μm. Size separation can separate polycaprolactone particles having diameters within a range desired for a particular end use, such as SLS printing. Size separation can be performed by sieving, cyclone separators, air classification, etc. Finally, the polycaprolactone or a sized fraction of the polycaprolactone may be used as a build material to manufacture an article. For example, a sized fraction of the polycaprolactone may be used as a build material in an SLS printer to manufacture 3D printed objects. In at least one variation, the size separation step is eliminated, and the powder is used in the end use application (e.g., SLS printing) without a size separation step.

[0073] Powder characterization Polycaprolactone powders precipitated according to some variations yielded the properties shown in Figures 2 through 5. Figure 2 shows results from a thermogravimetric analysis (TGA) performed on a sample of polycaprolactone produced according to at least one variation. In TGA, a sample is heated and its mass is measured as the temperature increases. The presence of residual solvent and the thermal decomposition temperature will be confirmed by the TGA results because they will appear as a change in the rate of mass loss. The second plot (line) on the TGA graph is the derivative of the TGA curve, showing the rate of mass change. As shown in Figure 2, the onset of decomposition in at least one variation began at 358°C, a 3% mass loss due to moisture.

[0074] Figure 3 shows a differential scanning calorimetry (DSC) curve of polycaprolactone precipitated according to at least one variation. As shown in the variation of Figure 3, the onset of the first melting peak is at 49.81°C, with a peak temperature of 58.39°C and an enthalpy of 101.86 J / g. The recrystallization peak in Figure 3 begins at 25.87°C, peaks at 21.02°C and has an enthalpy of 66.219 J / g. The second melting peak in Figure 3 begins at 45.68°C and has an enthalpy of 55.090 J / g.

[0075] In numerous variations, the use of ethyl lactate solvent has the following properties: (a) an onset decomposition temperature between about 287°C and about 420°C; (b) a TGA mass loss between about 0% and about 3% by weight; (c) a first melting onset temperature between about 49°C and about 58°C; (d) a first melting peak temperature between about 58°C and about 65°C; (e) a first melting peak enthalpy between about 97 J / g and about 111 J / g; (f) a first melting peak enthalpy between about 25°C and about 34°C; (g) a recrystallization onset temperature of between about 21°C and about 28°C; (h) a recrystallization enthalpy of between about 56 J / g and about 67 J / g; (i) a second melting onset temperature of between about 45°C and about 54°C; (j) a second melting peak temperature of between about 51°C and about 58°C; (k) a second melting enthalpy of between about 26 J / g and about 58 J / g; (l) a D, as determined by volume percent, of between about 32 μm and about 517 μm. 10 , (m) D between about 50 μm and about 944 μm, as determined by volume percent 50 , (n) D between about 83 μm and about 1297 μm, as determined by volume percent 90 (o) a volume percentage of particles having a diameter greater than 150 μm between about 0% and about 100% by volume; (p) a volume percentage of particles having a diameter less than 20 μm between 0% and 1% by volume; (q) a D between about 14 μm and about 245 μm, as determined by percentage. 10 , (r) D between 24 μm and 359 μm when determined in percent 50 , (s) D between 48 μm and 876 μm when determined in several percent 90, (t) a few percent of particles having a diameter greater than 150 μm, between about 0 and about 100 percent, or (u) a few percent of particles having a diameter less than 20 μm, between about 0 and about 35 percent.

[0076] When interpreting the data, D in y μm x means that x percent of the particles in the sample had a particle size smaller than y μm. For example, a D of 100 μm 50 (as determined by volume percent) means that 50% (by volume) of the particles in the sample had a particle size smaller than 100 μm.

[0077] In variations using ethyl lactate solvent, the method may produce polycaprolactone powders containing about 70 to about 100 volume percent of the particles having a particle size between 20 μm and 150 μm. Variations may produce polycaprolactone powders containing more than 80 volume percent, more than 90 volume percent, more than 95 volume percent, more than 98 volume percent, or even more than 99 volume percent of the particles having a particle size between 20 μm and 150 μm.

[0078] In variations using ethyl lactate solvent, the method may produce polycaprolactone powders containing particles in which about 70 to about 100 percent of the particles have a particle size between 20 μm and 150 μm. Variations may produce polycaprolactone powders in which more than 80 percent, more than 90 percent, more than 95 percent, more than 98 percent, or even more than 99 percent of the particles have a particle size between 20 μm and 150 μm. When the disclosed reprecipitation method is performed to produce polycaprolactone powders, analytical methods such as NMR (nuclear magnetic resonance spectroscopy), GC (gas chromatography), and TGA (thermogravimetric analysis) can be used to detect trace amounts of residual solvent in the polycaprolactone powder.

[0079] Using ethyl acetate solvent, the following characteristics were observed: (a) an onset decomposition temperature between about 329°C and about 475°C; (b) a TGA mass loss between about 0% and about 0.5% by weight; (c) a first melting onset temperature between about 52°C and about 57°C; (d) a first melting peak temperature between about 64°C and about 67°C; (e) a first melting peak enthalpy between about 96 J / g and about 105 J / g; (f) a first melting peak enthalpy between about 27°C and about 31°C; (g) a recrystallization onset temperature, (h) a recrystallization peak temperature between about 22°C and about 26°C, (i) a second melting onset temperature between about 50°C and about 60°C, (j) a second melting peak temperature between about 56°C and about 59°C, (k) a second melting enthalpy between about 50 J / g and about 55 J / g, (l) a D of about 28 μm, as determined by volume percent. 10 , (m) D of approximately 1066 μm, as determined by volume percent 50 , (n) D of approximately 1283 μm, as determined by volume percent 90 , (o) about 67% by volume of particles having a diameter greater than 150 μm, (p) about 1% by volume of particles having a diameter less than 20 μm, (q) about 46 μm D as determined by percentage 10 , (r) D of about 25 μm when determined in percent 50 , (s) D of about 3 μm when determined in a few percent 90 A polycaprolactone powder having at least one of: (t) about a few percent of particles having a diameter greater than 150 μm; or (u) about a few percent of particles having a diameter less than 20 μm.

[0080] The polycaprolactone produced according to at least one variation may have an intrinsic viscosity, determined in chloroform at 25°C, of ​​0.3 to 3.0 deciliters per gram (dl / gm), inclusive of the range endpoints. The polycaprolactone produced according to at least one variation may have an intrinsic viscosity, determined in chloroform at 25°C, of ​​1.1 to 1.4 deciliters per gram (dl / gm), inclusive of the range endpoints. The polycaprolactone may have a weight average molecular weight, measured by gel permeation chromatography (GPC) using a cross-linked styrene-divinylbenzene column and calibrated against polystyrene standards, of 5,000 to 200,000 daltons, specifically 100,000 to 150,000 daltons. GPC samples are prepared at a concentration of 1 mg per mL (mg / mL) and eluted at a flow rate of 1.5 mL per minute.

[0081] FIG. 4 shows a particle size volume distribution for SLS-grade powder produced according to at least one variation. According to at least one variation, such as that shown in FIG. 4, the distribution has a D of 62.14 μm. 10 , 102.2 μm D 50 , and D of 156.6 μm 90 It may be approximately Gaussian with

[0082] FIG. 5 shows the particle size number distribution for SLS-grade powder produced according to at least one variation. The distribution can be relatively constrained, with a dip around 100 μm and a D of 31.23 μm. 10 , 59.88 μm D 50 , and D of 105.0 μm 90 It has.

[0083] FIG. 6 shows powder data for polycaprolactone powder produced according to at least one variation. FIG. 6 shows that the polycaprolactone powder according to at least one variation had a peak melting temperature of 58.4°C. This figure also shows that the polycaprolactone produced according to at least one variation did not contain fine particles (defined as particles having a diameter of less than 20 μm). This may be beneficial in some applications, as fine particles may interfere with powder flowability. The spheroidal characteristics of particles produced according to at least one variation were also examined. 90.54% v / v (volume / volume or "volume percent") of the polycaprolactone particles had a sphericity greater than 0.75. 80.64% v / v of the polycaprolactone particles had a sphericity greater than 0.80. The sphericity values ​​were calculated according to Equation 1. D a is defined in Equation 2, and D p is defined by Equation 3. Higher sphericity values ​​correlate to better flowability. In at least one variation, polycaprolactone powders may be produced having a Hausner ratio of less than 1.25, where the Hausner ratio is defined as the ratio of tapped density to fluffy (bulk) density.

[0084]

number

[0085]

number

[0086]

number

[0087] SLS Test The polycaprolactone produced according to at least one variation may be blended with one or more other biocompatible components, such as hydroxyapatite. In at least one variation, the hydroxyapatite may be added to the polycaprolactone in an amount between 0.5% and 10% w / w of the mass of the polycaprolactone. Hydroxyapatite is a mineral found in both tooth enamel and bone and is used in bone tissue engineering. In variations, other components may be added to the polycaprolactone. The other components may include one or more types of glass fiber, carbon fiber, talc, clay, wollastonite, glass beads, or combinations thereof.

[0088] Polycaprolactone produced according to at least one variation was blended with 4% w / w hydroxyapatite (the mass of the hydroxyapatite was 4% of the mass of the polycaprolactone) and used in an SLS printer to produce tensile bars. Seven tensile bars were produced using a 40 W dual laser scan with a 0.18 mm scan gap, at a part temperature of 56.5°C and a feed temperature of 40°C. The tensile bars were then pulled using the ASTM D638-Type 4 tensile method. The pulling rate was 5.00 mm / min. Figure 7 is a photograph of an SLS-printed bar using polycaprolactone containing 4% w / w hydroxyapatite (HA). Figure 8A shows a tensile plot generated by pulling an SLS-produced polycaprolactone (containing 4% w / w hydroxyapatite) tensile bar. Figure 8B shows a summary of the material properties obtained from the tensile tests in Figure 8A.

[0089] According to at least one variation, the moisture content of the polycaprolactone / hydroxyapatite powder may be adjusted before using the powder in an SLS machine. Water may assist the melting process by acting as a heat sink. Hydroxyapatite may inhibit the melting process by acting as a desiccant. Hydroxyapatite may promote the melting of the polycaprolactone powder due to its IR absorption properties. Researchers have found that the amount of moisture (water) in the polycaprolactone / hydroxyapatite powder affects the quality of SLS-printed parts constructed with the material. Low moisture content of the polycaprolactone / hydroxyapatite may be detrimental to part quality. To ensure good printed part quality, water may be added to the polycaprolactone powder or a variation of the polycaprolactone / hydroxyapatite blend. For example, the moisture content of the polycaprolactone powder or polycaprolactone / hydroxyapatite blend may be adjusted to increase or decrease the moisture content of the powder. The moisture content may be adjusted, for example, by adding water to the powder or by placing the powder in a humidity-controlled atmosphere. The moisture content in the polycaprolactone powder or polycaprolactone / hydroxyapatite blend may be adjusted so that the moisture content of the powder is between 0.5% w / w and 5% w / w. In at least one variation, the powder may contain about 3% w / w water (moisture).

[0090] Nucleating agents such as hydroxyapatite In at least one variation, the solvent / polycaprolactone mixture may further include a nucleating agent.In at least one variation, the solvent / polycaprolactone mixture may further include hydroxyapatite as a nucleating agent.

[0091] Example procedure: Ethyl lactate (100 mL) was placed in a 250 mL Erlenmeyer flask and heated to 80°C. Once the set temperature was reached, polycaprolactone and hydroxyapatite were added. The polycaprolactone was added at a 12% w / v (g / mL) loading in the solvent, and the hydroxyapatite was added at 4% w / w of the polycaprolactone. The mixture was stirred until the polymers were completely dissolved, then the heat was removed and reprecipitation occurred. When the mixture had precipitated to the point where the stir bar could no longer be moved, it was filtered to recover the solvent, washed with room temperature deionized water for 3 hours, filtered, and air-dried in an evaporating dish for 72 hours.

[0092] observation: When the polycaprolactone dissolved, the solution remained opaque, probably due to the hydroxyapatite particles (which are not soluble in ethyl lactate).

[0093] Within 2 hours of removing the heat, the mixture precipitated. At the 250 mL scale, this was twice as fast as the polycaprolactone solution without the nucleating agent. 43.5% of the ethyl lactate was recovered.

[0094] Powder analysis: 9 shows DSC curves of the resulting polycaprolactone powder nucleated with hydroxyapatite according to at least one variation. The first melting curve has a peak at 62.42°C and an enthalpy of 101.68 J / g. The recrystallization curve has a peak at 26.62°C and an enthalpy of 59.38 J / g. The second melting curve has a peak at 57.80°C and an enthalpy of 45.78 J / g.

[0095] Figure 10 shows the D of 19.14 μm with at least one variation. 10 , 30.58 μm D 50 , and D of 53.13 μm 901 shows the particle number size distribution having a particle size distribution of 12.74% of all particles outside the desired SLS range (the desired SLS range is a particle size range between 20 μm and 150 μm), with 99.95% of all particles smaller than 150 μm and 12.69% of particles smaller than 20 μm.

[0096] Figure 11 shows the D of 31.47 μm with at least one variation. 10 , 61.25 μm D 50 , and D of 120.6 μm 90 1 shows the particle number size distribution having a particle size distribution of 0.91% to 1.02%. Only 4.04% of the total particles are outside the desired SLS range (the desired SLS range would be 20 μm to 150 μm), with 96.87% of the total particles being smaller than 150 μm and 0.91% of the particles being smaller than 20 μm.

[0097] Compared to powder without nucleating agent: Figures 12A and 12B show a comparison of polycaprolactone powder nucleated with 4% w / w hydroxyapatite (12A) and polycaprolactone powder blended with 4% w / w hydroxyapatite and allowed to stand for 24 hours (12B). The figures (Figures 12A and 12B) compare pucks prepared by melting approximately 8 g of polycaprolactone / hydroxyapatite blend. Sample "(12A)" had 4% w / w hydroxyapatite added prior to reprecipitation, which acted as a nucleating agent. Sample "(12B)" had 4% w / w hydroxyapatite added after powder sieving in a dry blend form.

[0098] In variations in which hydroxyapatite is added as a nucleating agent, the hydroxyapatite may be added during the polycaprolactone precipitation process to form a solution containing hydroxyapatite, polycaprolactone, and solvent. In at least one variation, the amount of hydroxyapatite may be added to the solvent / solution such that the hydroxyapatite is present in an amount between 0.5% w / w and 10% w / w of the mass of the polycaprolactone. The polycaprolactone may then precipitate from the solution to form a precipitated polycaprolactone powder containing hydroxyapatite. This method may be used to prepare pucks, such as the puck shown in FIG. 12A as puck "(12A)." The puck preparation method may include melting a polycaprolactone-containing material and then allowing the material to cool and solidify.

[0099] In variations in which hydroxyapatite is dry-blended with polycaprolactone, the polycaprolactone may be precipitated from a solvent and dried. The dried polycaprolactone may then be blended with an amount of hydroxyapatite to form a powder containing polycaprolactone and hydroxyapatite. This method may be used to prepare pucks, such as the puck shown in FIG. 12B as puck "(12B)." The puck preparation method may include melting a polycaprolactone-containing material and then allowing the material to cool and solidify.

[0100] Figure 13 shows a comparison of particle size distribution between polycaprolactone precipitated as is and polycaprolactone precipitated with hydroxyapatite acting as a nucleating agent. As shown in Figure 13, the addition of hydroxyapatite as a nucleating agent in the reprecipitation step can improve the particle size distribution, resulting in more polycaprolactone particles falling within the range of 20 to 150 μm.

[0101] Both volume and number distributions are considered when determining whether a powder is suitable for SLS. In an ideal situation, the volume and number distributions are identical, and D50 The average particle size is 60 μm, with a distribution between 30 μm and 150 μm, with minimal powder outside that range. However, in practice, this is not the case. Therefore, the volume distribution is looked at to determine whether the powder is suitable for SLS, and the number distribution is looked at to determine whether there are any potential problems that may arise. For example, too many particles smaller than 30 μm or smaller than 20 μm can cause flow problems, while too many particles larger than 150 μm can cause resolution problems.

[0102] Figure 13 shows a comparison between the particle size distributions of polycaprolactone precipitated with and without hydroxyapatite acting as a nucleating agent. Looking at the volume distribution, both powders have a relatively Gaussian distribution, but the polycaprolactone precipitated with hydroxyapatite has a nearly ideal D 50 In addition, the hydroxyapatite-precipitated polycaprolactone has a lower volume percentage of particles outside the desired range (which can be a particle size range between 20 μm and 150 μm diameter, inclusive). Looking at the number distribution, the hydroxyapatite-precipitated polycaprolactone has 12.7% more particles smaller than 20 μm than polycaprolactone without a nucleating agent. However, for a near-ideal volume distribution, the polycaprolactone powder with a nucleating agent would be preferred.

[0103] Figure 14A shows a pack prepared by melting virgin polycaprolactone in a convection oven (at ambient humidity). Figure 14A shows two opposite sides (top and bottom) of a single pack, as shown in Figures 14B-G. Figure 14B shows a pack prepared by melting virgin polycaprolactone under IR (infrared) light (at ambient humidity). Figure 14C shows a pack prepared by dry-blending freshly made polycaprolactone with 4% w / w hydroxyapatite and then melting in a convection oven. Figure 14D shows a pack prepared by dry-blending freshly made polycaprolactone with 4% w / w hydroxyapatite and then melting under IR light. Figure 14E shows a pack prepared by dry-blending 4% w / w hydroxyapatite with polycaprolactone, aging the blend at ambient conditions for 24 hours, and then melting the aged blend in a convection oven. Figure 14F shows a puck prepared by dry-blending 4% w / w hydroxyapatite with polycaprolactone, aging the blend at ambient conditions for 24 hours, and then melting the aged blend under IR. Figure 14G shows a puck prepared by melting polycaprolactone containing 4% w / w hydroxyapatite as a nucleating agent formed by a powder precipitation process (i.e., hydroxyapatite was added to a solvent during precipitation to form a solution containing hydroxyapatite, polycaprolactone, and solvent) in a convection oven. As shown in Figure 14G, adding hydroxyapatite as a nucleating agent during the precipitation of polycaprolactone in ethyl lactate produced a puck with a homogeneous appearance. In other words, without being bound by theory, the use of hydroxyapatite as a nucleating agent during the precipitation process appears to result in a molten mass with uniform concentrations of hydroxyapatite and polycaprolactone throughout the mass, resulting in a molten mass that appears to be well-mixed.

[0104] Figure 15 shows the DSC curve of polycaprolactone powder reprecipitated in ethyl lactate. As shown in the figure, the polycaprolactone was first heated to 100°C at a heating rate of 20°C per minute. The first melting peak temperature was 58.39°C, with a melting enthalpy of 99.928 J / g. The polycaprolactone sample was then cooled to -10°C at a cooling rate of 20°C per minute. The recrystallization peak temperature was 21.02°C, with a melting enthalpy of 62.261 J / g. The polycaprolactone sample was then heated a second time to 100°C at a rate of 20°C per minute (as shown by the dashed line at the bottom of Figure 15). The second heating cycle showed a melting peak temperature of 51.22°C and a melting enthalpy of 52.677 J / g.

[0105] FIG. 16 shows the DSC curve of polycaprolactone powder (in ethyl lactate) reprecipitated in the presence of 4% w / w hydroxyapatite as a nucleating agent, where 4% w / w hydroxyapatite was calculated by dividing the mass of hydroxyapatite added to the ethyl lactate by the mass of polycaprolactone added to the ethyl lactate. The DSC protocol used to generate the data in FIG. 16 was the same as that used to generate the data in FIG. 15. First, the sample was heated to 100° C. at a heating rate of 20° C. / min, then the sample was cooled to −10° C. at a rate of 20° C. / min, and then the sample was heated again to 100° C. at a heating rate of 20° C. / min. As shown in FIG. 16, the polycaprolactone sample reprecipitated in the presence of hydroxyapatite as a nucleating agent had a first melting peak temperature of 62.42° C. and an enthalpy of 101.68 J / g. The sample had a recrystallization peak temperature of 26.62° C. and an enthalpy of 59.376 J / g. Finally, the sample had a second peak melting temperature of 57.80° C. and an enthalpy of 45.775 J / g. Preferred embodiments of the present invention will be described below in detail. Embodiment 1 1. A powder comprising polycaprolactone particles, wherein greater than 90 volume percent of the polycaprolactone particles have a particle size between 20 micrometers and 150 micrometers, the polycaprolactone particles containing a detectable amount of a nucleating agent, and the polycaprolactone particles containing a detectable amount of a solvent, the solvent comprising at least one of a biocompatible solvent or a bioabsorbable solvent. Embodiment 2 2. The powder of embodiment 1, wherein the solvent comprises ethyl lactate. Embodiment 3 2. The powder of embodiment 1, wherein the nucleating agent is hydroxyapatite. Embodiment 4 2. The powder of embodiment 1, wherein greater than 90 volume percent of the polycaprolactone particles have a sphericity greater than 0.75. Embodiment 5 2. The powder of embodiment 1, wherein greater than 80 volume percent of the polycaprolactone particles have a sphericity greater than 0.80. Embodiment 6 2. The powder of embodiment 1, wherein the volume percentage of polycaprolactone particles having a particle size of less than 20 micrometers is zero or undetectable. Embodiment 7 2. The powder of embodiment 1, wherein the powder has a fusion enthalpy of about 90 J / g to about 120 J / g. Embodiment 8 A powder comprising polycaprolactone particles, a detectable amount of ethyl lactate, and a detectable amount of a nucleating agent, the powder having a peak melting temperature of about 55°C to about 65°C and a melting enthalpy of about 90 J / g to about 120 J / g. Embodiment 9 9. The powder of embodiment 8, wherein the nucleating agent is hydroxyapatite. Embodiment 10 9. The powder of embodiment 8, wherein the powder has a recrystallization peak of from about 15°C to about 35°C. Embodiment 11 9. The powder of embodiment 8, wherein the powder has an onset decomposition temperature of from about 250°C to about 425°C. Embodiment 12 9. The powder of embodiment 8, wherein greater than 96 percent of the polycaprolactone particles have a particle size of less than 125 micrometers. Embodiment 13 9. The powder of embodiment 8, wherein greater than 90 volume percent of the polycaprolactone particles have a sphericity greater than 0.75. Embodiment 14 1. A powder comprising polycaprolactone particles having a detectable amount of ethyl lactate and a detectable amount of a nucleating agent, wherein greater than 96 percent by number of the polycaprolactone particles have a particle size of less than 125 micrometers, 90 percent by volume of the polycaprolactone particles have a sphericity greater than 0.75, and the polycaprolactone particles have a moisture content adjusted to and maintained between 0.5% w / w and 5% w / w. Embodiment 15 15. The powder of embodiment 14, wherein the nucleating agent is hydroxyapatite. Embodiment 16 10. The method of producing a powder according to claim 1, further comprising: combining polycaprolactone and a polar organic solvent; dissolving the polycaprolactone in the polar organic solvent to form a solution; cooling the solution to a temperature that causes at least a portion of the dissolved polycaprolactone to precipitate from the solution; adding a nucleating agent to the solution; separating the precipitated polycaprolactone from the solution; washing the separated precipitated polycaprolactone to form washed polycaprolactone; and drying the washed polycaprolactone to form dried polycaprolactone; The method comprising: Embodiment 17 17. The method of embodiment 16, further comprising heating the combined polycaprolactone and the polar organic solvent. Embodiment 18 17. The method of embodiment 16, further comprising a separating step of separating dry polycaprolactone particles having a particle size of less than 150 micrometers from larger dry polycaprolactone particles to form sized polycaprolactone. Embodiment 19 19. The method of embodiment 18, wherein the percent of nucleating agent in the combined polycaprolactone / nucleating agent mixture is between about 0.5 weight percent and about 10 weight percent. Embodiment 20 17. The method of embodiment 16, wherein the nucleating agent is hydroxyapatite. Embodiment 21 19. The method of embodiment 18, wherein greater than 90 volume percent of the sized polycaprolactone has a sphericity greater than 0.75. Embodiment 22 19. The method of embodiment 18, wherein greater than 80 volume percent of the sized polycaprolactone has a sphericity greater than 0.80. Embodiment 23 17. The method of embodiment 16, wherein the polar organic solvent is selected from the group consisting of ethyl acetate, ethyl lactate, gamma-valerolactone, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dichloromethane (DCM), chloroform, acetone, and dimethyl sulfoxide (DMSO). Embodiment 24 24. The method of embodiment 23, wherein the polar organic solvent is ethyl lactate. Embodiment 25 10. The method of producing a powder according to claim 1, further comprising: combining polycaprolactone and ethyl lactate; dissolving the polycaprolactone and at least one nucleating agent in the ethyl lactate to form a solution; cooling the solution to a temperature that causes at least a portion of the dissolved polycaprolactone to precipitate from the solution; separating the precipitated polycaprolactone from the solution; washing the separated precipitated polycaprolactone to form washed polycaprolactone; and drying the washed polycaprolactone to form dried polycaprolactone; The method comprising: Embodiment 26 26. The method of embodiment 25, wherein the at least one nucleating agent comprises hydroxyapatite. Embodiment 27 26. The method of embodiment 25, wherein the solution is heated. Embodiment 28 In the additive manufacturing method, selectively fusing or sintering adjacent polycaprolactone particles; Including, greater than 96 percent by volume of the polycaprolactone particles have a particle size of less than 125 micrometers, and greater than 90 percent by volume of the polycaprolactone particles have a sphericity greater than 0.75; the polycaprolactone particles contain a detectable amount of hydroxyapatite; The polycaprolactone particles contain a detectable amount of ethyl lactate. Embodiment 29 29. The method of embodiment 28, wherein said polycaprolactone particles have a moisture content adjusted to and maintained between 0.5% w / w and 5% w / w. Embodiment 30 10. An article made from the powder of embodiment 1. Embodiment 31 10. A medical product made from the powder of embodiment 1.

Claims

1. a powder comprising polycaprolactone particles, greater than 90 volume percent of the polycaprolactone particles having a particle size between 20 micrometers and 150 micrometers, the polycaprolactone particles containing a detectable amount of a nucleating agent, and the polycaprolactone particles containing a detectable amount of a solvent, the solvent comprising at least one of a biocompatible solvent or a bioabsorbable solvent; A powder having zero or undetectable volume percent of polycaprolactone particles having a particle size of less than 20 micrometers.

2. 10. The powder of claim 1, wherein the solvent comprises ethyl lactate.

3. 2. The powder of claim 1, wherein the nucleating agent is hydroxyapatite.

4. 10. The powder of claim 1, wherein greater than 90 volume percent of the polycaprolactone particles have a sphericity greater than 0.

75.

5. 10. The powder of claim 1, wherein greater than 80 volume percent of the polycaprolactone particles have a sphericity greater than 0.

80.

6. 10. The powder of claim 1, wherein the powder has a fusion enthalpy of about 90 J / g to about 120 J / g.

7. A powder comprising polycaprolactone particles, a detectable amount of ethyl lactate, and a detectable amount of a nucleating agent, the powder having a peak melting temperature of about 55°C to about 65°C, a melting enthalpy of about 90 J / g to about 120 J / g, and an onset decomposition temperature of about 250°C to about 425°C.

8. 8. The powder of claim 7, wherein the nucleating agent is hydroxyapatite.

9. 8. The powder of claim 7, wherein the powder has a recrystallization peak at about 15°C to about 35°C.

10. 8. The powder of claim 7, wherein greater than 96 percent of the polycaprolactone particles have a particle size of less than 125 micrometers.

11. 8. The powder of claim 7, wherein greater than 90 volume percent of the polycaprolactone particles have a sphericity greater than 0.

75.

12. 1. A powder comprising polycaprolactone particles having a detectable amount of ethyl lactate and a detectable amount of a nucleating agent, wherein greater than 96 percent by number of the polycaprolactone particles have a particle size of less than 125 micrometers, 90 percent by volume of the polycaprolactone particles have a sphericity greater than 0.75, and the polycaprolactone particles have a moisture content adjusted to and maintained between 0.5% w / w and 5% w / w.

13. 13. The powder of claim 12, wherein the nucleating agent is hydroxyapatite.

14. 2. The method for producing the powder of claim 1, combining polycaprolactone and a polar organic solvent; dissolving the polycaprolactone in the polar organic solvent to form a solution; cooling the solution to a temperature that causes at least a portion of the dissolved polycaprolactone to precipitate from the solution; adding a nucleating agent to the solution; separating the precipitated polycaprolactone from the solution; washing the separated precipitated polycaprolactone to form washed polycaprolactone; drying the washed polycaprolactone to form dried polycaprolactone; and separating dry polycaprolactone particles having a particle size of less than 150 micrometers from larger dry polycaprolactone particles to form sized polycaprolactone; The method comprising:

15. 15. The method of claim 14, further comprising the step of heating the combined polycaprolactone and the polar organic solvent.

16. 15. The method of claim 14, wherein the percent of nucleating agent in the combined polycaprolactone / nucleating agent mixture is between about 0.5 weight percent and about 10 weight percent.

17. The method of claim 14, wherein the nucleating agent is hydroxyapatite.

18. 15. The method of claim 14, wherein greater than 90 volume percent of the sized polycaprolactone has a sphericity greater than 0.

75.

19. 15. The method of claim 14, wherein greater than 80 volume percent of the sized polycaprolactone has a sphericity greater than 0.

80.

20. 15. The method of claim 14, wherein the polar organic solvent is selected from the group consisting of ethyl acetate, ethyl lactate, γ-valerolactone, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), dichloromethane (DCM), chloroform, acetone, and dimethyl sulfoxide (DMSO).

21. 21. The method of claim 20, wherein the polar organic solvent is ethyl lactate.

22. 2. The method for producing the powder of claim 1, combining polycaprolactone and ethyl lactate; dissolving the polycaprolactone and at least one nucleating agent in the ethyl lactate to form a solution; cooling the solution to a temperature that causes at least a portion of the dissolved polycaprolactone to precipitate from the solution; separating the precipitated polycaprolactone from the solution; washing the separated precipitated polycaprolactone to form washed polycaprolactone; and drying the washed polycaprolactone to form dried polycaprolactone; The method comprising:

23. 23. The method of claim 22, wherein the at least one nucleating agent comprises hydroxyapatite.

24. 23. The method of claim 22, wherein the solution is heated.

25. In the additive manufacturing method, selectively fusing or sintering adjacent polycaprolactone particles; Including, greater than 96 percent by number of the polycaprolactone particles have a particle size less than 125 micrometers, and greater than 90 percent by volume of the polycaprolactone particles have a sphericity greater than 0.75; the polycaprolactone particles contain a detectable amount of hydroxyapatite; The polycaprolactone particles contain a detectable amount of ethyl lactate.

26. 26. The method of claim 25, wherein the polycaprolactone particles have a moisture content adjusted and maintained between 0.5% w / w and 5% w / w.

27. 10. An article made from the powder of claim 1.

28. A medical product made from the powder of claim 1.

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