Powder for additive manufacturing, production processess thereof, and articles or devices made thereof

Abstract

The present invention relates to the field of additive manufacturing, preferably for producing articles and devices such as medical devices. More specifically, the present invention relates to a powder comprising spherical polyester particles, production processes thereof, and the use of said powder in additive manufacturing.

Description

[0001] POWDER FOR ADDITIVE MANUFACTURING, PRODUCTION PROCESSESS THEREOF, AND ARTICLES OR DEVICES MADE THEREOF

[0002] FIELD OF THE INVENTION

[0003] The present invention generally relates to the field of additive manufacturing, preferably for producing articles and devices such as medical devices. More specifically, the present invention relates to a powder comprising spherical polyester particles, production processes thereof, and the use of said powder in additive manufacturing.

[0004] BACKGROUND OF THE INVENTION

[0005] In recent years, additive manufacturing processes such as sintering-based printing have been introduced to manufacture various articles and devices, including medical devices, implants, and tissue engineering scaffolds. In sintering, a powder comprising particles of a polymer material are fused together by applying heat or pressure, creating a solid object without fully melting the material. This method is widely used in producing bioresorbable devices because it offers precision, material customization, and the ability to create complex geometries.

[0006] Bioresorbable devices may be produced in the form of implants or medical scaffolds that can degrade and be absorbed by the body over time. The integration of sintering in the additive manufacturing process for bioresorbable polymers allows for the fabrication of patient-specific medical devices with tailored shapes, degradation rates, porosity, and / or mechanical properties.

[0007] Existing sintering powders typically require the use of flow aids, solvents, or other additives such as nucleators or surfactants to improve the flowability of the powder and deposit layers of powder with uniform thickness during manufacturing. Nevertheless, while flow aids may improve powder flowability, their use also has several drawbacks. Similar to many other additives, the addition of flow aids may lead to inconsistent sintering because the flow aid particles may act as crystallization initiators or inhibitors, act as seeds for early fusion of particles, or hinder fusion of particles during melting. As a consequence, this may narrow the available processing window as the powder becomes more temperature sensitive, leading to less stable manufacturing processes and possibly higher scrap rates. A changing thermal behaviour may also lead to degradation of the polymer or compromise its bioresorbable properties. The addition of flow aids may further be undesirable to medical implants because their addition might result in adverse effects in a patient's body.

[0008] Accordingly, it is an object of the present invention to provide a powder that overcomes one or more of the above-mentioned issues, and processes for producing the same. More specifically, it is an objective of the present invention to provide an improved process for producing a powder for additive manufacturing with improved flowability, without the need for solvents and additives such as flow aids, nucleators, nor surfactants.

[0009] Another objective of the present invention is to provide an improved powder for additive manufacturing that minimizes or eliminates the need for additives, without compromising processability and product quality.

[0010] Another objective of the present invention is to provide an improved powder that allows for a broader processing window.

[0011] It is also an objective of the present invention to provide an improved additive manufacturing process, using the powder as described herein.

[0012] It is also an objective of the present invention to provide an improved device, preferably a medical device, with high shape fidelity, good mechanical properties, biocompatibility, smooth surface finish, and high structural integrity.

[0013] SUMMARY OF THE INVENTION

[0014] It has now surprisingly been found that some or all of the above objectives can be attained either individually or in any combination by using the process for producing a powder for additive manufacturing comprising spherical polyester particles as presently claimed, and (preferred) embodiments thereof.

[0015] An advantage of the present invention is that the disclosed process produces a powder that exhibits good flowability and is less prone to particle agglomeration. Moreover, the present inventors have discovered that less stringent working conditions may be needed when using the aforementioned powder in an additive manufacturing process, which results in a higher manufacturing efficiency with significantly lower scrap rates. Furthermore, by eliminating the requirement for flow aids, solvents, or other additives, concerns about biocompatibility of the manufactured objects and devices may be alleviated.

[0016] Another advantage of the present invention is that articles and devices manufactured from the produced powder may also exhibit a higher density, decreased porosity, higher mechanical strength, and a smoother surface finish when compared to articles and devices made from commercially available powders comprising flow aids or other additives. This can advantageously reduce the need for additional post-processing steps to e.g., improve surface finish, mechanical strength, or remove unsintered powder, which decreases manufacturing time and complexity.

[0017] To that end, the present invention relates in a first aspect to a process for producing a powder for additive manufacturing. The process preferably comprises the steps of a) providing a powder comprising irregular polyester particles, preferably irregular polycaprolactone particles; b) subjecting the powder comprising irregular polyester particles to thermal spheroidization by heating said powder above the peak melting temperature of the irregular polyester particles and subsequently cooling the powder, thereby obtaining a powder comprising spherical polyester particles; and, c) annealing the powder comprising spherical polyester particles, thereby obtaining the powder for additive manufacturing.

[0018] The present inventors have found that the combination of process steps as recited herein may provide a powder with improved flowability and a reduced tendency for agglomeration. This is particularly advantageous for uniform layer deposition and controlled packing of the particles during manufacturing, which may reduce porosity and defects and lead to stronger, more reliable parts.

[0019] Another advantage of the present powder production process is that a powder with a desirable particle distribution and particle size may be obtained.

[0020] Yet another advantage of the present process is that it may eliminate the need for solvents or additives, which typically impact regulatory compliance (e.g., biocompatibility) and / or increase production costs.

[0021] In some preferred embodiments, the polyester is selected from the group comprising polycaprolactone, polylactide, polyglycolide, polydioxanone, polyhydroxybutyrate, polyhydroxyvalerate, and copolymers thereof and / or mixtures thereof; preferably wherein the polyester comprises polycaprolactone or is polycaprolactone. For the manufacturing of medical devices in particular, polycaprolactone (and copolymers thereof as described herein) may offer several advantages such as tuneable biodegradation, biocompatible degradation products, and good mechanical strength.

[0022] In some preferred embodiments, the powder is free or essentially free from any flow aids and calcium phosphates, such as hydroxyapatite. In some preferred embodiments, step c) comprises heating the powder comprising spherical polyester particles to a temperature between the recrystallization temperature and peak melting temperature of the spherical polyester particles for at least 5 hours and subsequently cooling the powder.

[0023] In some preferred embodiments, heating the powder comprising spherical polyester particles in step c) comprises heating to a temperature between 5°C above the recrystallization temperature and 1°C below the peak melting temperature of the spherical polyester particles.

[0024] In some preferred embodiments, the step of subsequently cooling the powder in step c) comprises cooling to a temperature of between 20°C and 25°C at a cooling rate of between 0.1°C / min and 1.0°C / min.

[0025] The present inventors have found that the particle size and particle size distribution of the spherical polyester particles may influence the processability and stability of the present powder.

[0026] In some preferred embodiments, the powder for additive manufacturing comprises spherical polyester particles with a particle size distribution D50 of between 40.0 pm and 100.0 pm, or between 45.0 pm and 100.0 pm, or between 50.0 pm and 100.0 pm, or between 55.0 pm and 100.0 pm, or between 60.0 pm and 100.0 pm, or between 60.0 pm and 95.0 pm, or between 60.0 pm and 90.0 pm, or between 65.0 pm and 90.0 pm.

[0027] In some preferred embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with an average particle size of from at least 10.0 pm to at most 150.0 pm, or at least 20.0 pm to at most 150.0 pm, or at least 30.0 pm to at most 150.0 pm, or at least 40.0 pm to at most 150.0 pm, or at least 40.0 pm to at most 140.0 pm, or at least 40.0 pm to at most 130.0 pm, or at least 40.0 pm to at most 120.0 pm, or at least 40.0 pm to at most 110.0 pm, or at least 40.0 pm to at most 100.0 pm, or at least 50.0 pm to at most 100.0 pm.

[0028] In some preferred embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with a circularity of greater than 0.80, or greater than 0.85, or greater than 0.86, or greater than 0.87, or greater than 0.88, or greater than 0.89, or greater than 0.90.

[0029] In some preferred embodiments, the thermal spheroidization process of step b) comprises bringing the powder comprising irregular polyester particles into suspension in a carrier gas, heating said powder by means of radiation generated by a radiation source, leading to spheroidization, and cooling the gas-carried suspension. In other embodiments, the thermal spheroidization process of step b) comprises bringing the powder comprising irregular polyester particles into suspension in a liquid medium that is immiscible with molten polyester, such as an oil, heating the medium to above the melting temperature of the powder, leading to spheroidization, and quenching the suspension.

[0030] In some preferred embodiments, the powder comprising irregular polyester particles is obtained by grinding polyester material, preferably wherein grinding comprises cryogenic grinding.

[0031] The present invention further encompasses a powder for additive manufacturing obtained or obtainable by means of the process according to a first aspect of the present invention or (preferred) embodiments thereof.

[0032] According to a second aspect, the present invention relates to a powder for additive manufacturing, the powder comprising spherical polyester particles, wherein greater than 50 vol. % (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polyester particles have an average particle size of from at least 10.0 pm to at most 150.0 pm; and a circularity of greater than 0.80.

[0033] It should be clear that (preferred) embodiments of the process according to a first aspect of the invention and associated advantages thereof are also (preferred) embodiments of the powder according to a second aspect of the invention and vice versa.

[0034] In preferred embodiments, the powder comprises spherical polyester particles, wherein greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polyester particles have an average particle size of from at least 10.0 pm to at most 150.0 pm; and a circularity of greater than 0.85; and preferably an aspect ratio of greater than 0.75.

[0035] According to a third aspect, the present invention relates to an additive manufacturing process. The process preferably comprises the steps of: i) providing the powder obtained or obtainable by means of the process according to a first aspect of the present invention or (preferred) embodiments thereof; or the powder according to the second aspect of the present invention or (preferred) embodiments thereof; and, ii) selectively bonding, e.g., sintering, fusing, or melting, the powder particles, thereby obtaining a printed article or device. It has been found herein that the present powder allows for optimization of processing temperatures and scanning speeds during additive manufacturing, which may reduce energy consumption and processing time. In addition, more consistent powder properties may lead to a stable manufacturing process, which is essential for meeting regulatory standards in medical device production.

[0036] Another advantage of the present additive manufacturing process is that it may provide for a costefficient production process with reduced waste and improved material quality.

[0037] It should be clear that (preferred) embodiments of the first aspect of the invention, the second aspect of the invention and associated advantages thereof are also (preferred) embodiments of the additive manufacturing process according to the third aspect of the invention and vice versa. The same reasoning applies mutatis mutandis to products directly obtained by said processes.

[0038] In some preferred embodiments, additive manufacturing comprises powder bed fusion, and preferably selective laser sintering, selective heat sintering, highspeed sintering, or multi-jet fusion.

[0039] According to a fourth aspect, the present invention further encompasses a device, preferably a medical device, obtained or obtainable by means of the process according to a third aspect of the present invention or preferred) embodiments thereof.

[0040] In some preferred embodiments, the device, preferably the medical device, may be manufactured from the powder according to an aspect of the invention, or manufactured by means of the process according to a third aspect of the present invention or preferred) embodiments thereof.

[0041] In some preferred embodiments, the device is a bioresorbable implant, preferably a breast implant, splint, stent, tissue-regeneration scaffold, drug-delivery device, or fixation device.

[0042] It should be clear that (preferred) embodiments of the first aspect of the invention, the second aspect of the invention, the third aspect of the invention, and associated advantages thereof are also (preferred) embodiments of the fourth aspect of the invention and vice versa.

[0043] According to a fifth aspect, the present invention relates to the use of the powder obtained or obtainable by means of the process according to a first aspect of the present invention or (preferred) embodiments thereof; or the powder according to the second aspect of the present invention or (preferred) embodiments thereof, in an additive manufacturing process, preferably an additive manufacturing process comprising powder bed fusion.

[0044] It should be clear that (preferred) embodiments of the first aspect of the invention, the second aspect of the invention, the third aspect of the invention, the fourth aspect of the invention, and associated advantages thereof are also (preferred) embodiments of the fifth aspect of the invention and vice versa.

[0045] The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, which illustrate, by way of example, the principles of the invention.

[0046] DESCRIPTION OF THE FIGURES

[0047] The teaching of the application is illustrated by the following Figures which are to be considered as illustrative only and do not in any way limit the scope of the claims.

[0048] FIG. 1 is a DSC thermogram illustrating the thermal properties of the powder of example 1 prior to annealing.

[0049] FIG. 2 illustrates the result of a rotating-drum flowability test at 45°C of the powder of example 1 prior to annealing.

[0050] FIG. 3 illustrates the result of a rotating-drum flowability test at 55°C of the powder of example 1 prior to annealing.

[0051] FIG. 4 is a DSC thermogram illustrating the thermal properties of the powder of example 1 after annealing including heating for 13 hours.

[0052] FIG. 5 is a DSC thermogram illustrating the thermal properties of the powder of example 1 after annealing including heating for 67 hours.

[0053] FIG. 6A-C illustrates a selective-laser-sintering step wherein a new layer of powder is deposited.

[0054] FIG. 7 illustrates a selective-laser-sintering step wherein a new layer of commercially available powder is deposited.

[0055] FIG. 8A-C illustrate the distribution of shape parameters circularity (CR), sphericity (SP), and aspect ratio (AR) of the powder of example 1 and cryo-milled PCL powder.

[0056] FIG. 9 illustrates a comparison of the mechanical properties of a test sample printed from a powder of example 1 at low Ev-values (~95 J cm'3) and a test sample printed from a powder of example 1 at high Ev-values (~126 J cm'3).

[0057] FIG. 10 illustrates a visual comparison of sample failure modes during tensile testing of A) a test sample printed from a powder of example 1 at low Ev-values (~95 J cm'3); and B) a test sample printed from a powder of example 1 at high Ev-values (~126 J cm'3). FIG. 11 illustrates a graph showing the evolution break strain (%) as a function of Evapplied during printing for test samples printed from a powder of example 1 .

[0058] DETAILED DESCRIPTION OF THE INVENTION

[0059] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0060] The discussion of the background to the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known, or part of the common general knowledge in any country as of the priority date of any of the claims.

[0061] As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a step" means one step or more than one step.

[0062] The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements, or method steps. The terms also encompass "consisting of" and "consisting essentially of", which enjoy well-established meanings in patent terminology.

[0063] Whereas the terms "one or more" or "at least one", such as one or more members or at least one member of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members. In another example, "one or more" or "at least one" may refer to 1, 2, 3, 4, 5, 6, 7 or more.

[0064] The terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the disclosure described herein are capable of operation in other sequences than described or illustrated herein. As used herein, the term "and / or" when used in a list of two or more items, means that any one of the listed items can be employed by itself or any combination of two or more of the listed items can be employed. For example, if a list is described as comprising group A, B, and / or C, the list can comprise A alone, B alone, C alone, A and B in combination, A and C in combination, B and C in combination, or A, B, and C in combination.

[0065] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" or "in a particular embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while certain embodiments described herein include some, but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art.

[0066] The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1, 2, 3, 4 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of endpoints also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all subranges subsumed therein. This applies to numerical ranges irrespective of whether they are introduced by the expression "from... to..." or the expression "between... and..." or another expression.

[0067] As used herein, the terms "about" or "approximately" are used to provide flexibility to a numerical value or range endpoint by providing that a given value may be "a little above" or "a little below" said value or endpoint, depending on the specific context. Hence, the terms "about" or "approximately" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, are meant to encompass variations of and from the specified value or endpoint, such as variations of + / -10% or less, preferably + / -5% or less, more preferably + / -1% or less, and still more preferably + / -0.1% or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. Unless otherwise stated, use of the terms "about" or "approximately" in accordance with a specific number or numerical range should also be understood to provide support for such numerical terms or range without the term "about". For example, the recitation of "about 30" should be construed as not only providing support for values a little above and a little below 30, but also for the actual numerical value of 30 as well.

[0068] As used herein, the term "substantially" refers to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. For example, an object that is "substantially" enclosed would mean that the object is either completely enclosed or nearly completely enclosed. The exact allowable degree of deviation from absolute completeness may in some cases depend on the specific context. However, generally speaking the nearness of completion will be so as to have the same overall result as if absolute and total completion were obtained. The use of "substantially" is equally applicable when used in a negative connotation to refer to the complete or near complete lack of an action, characteristic, property, state, structure, item, or result.

[0069] The terms "wt.%," "vol%", or "mol%" refers to a weight percentage of a component, a volume percentage of a component, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, which includes the component.

[0070] Reference in this specification may be made to powders, devices, articles, or processes that provide "improved" performance (e.g. increased or decreased results, depending on the context). It is to be understood that unless otherwise stated, such "improvement" is a measure of a benefit obtained based on a comparison to powders, devices, articles, or processes in the prior art. Furthermore, it is to be understood that the degree of improved performance may vary between disclosed embodiments and that no equality or consistency in the amount, degree, or realization of improved performance is to be assumed as universally applicable.

[0071] Objects described herein as being "adjacent" to each other reflect a functional relationship between the described objects, that is, the term indicates the described objects must be adjacent in a way to perform a designated function which may be a direct ( / .e. physical) or indirect ( / .e. close to or near) contact, as appropriate for the context in which the phrase is used.

[0072] The term "bioresorbable" as used herein refers to a material that is designed to degrade and be absorbed by the body after fulfilling its intended (medical) function. These materials undergo a controlled breakdown process, typically through hydrolysis or enzymatic action, and their byproducts are either metabolized or excreted by the body. The degradation rate of a material can be tailored depending on the specific application, such as temporary implants or scaffolds for tissue regeneration, eliminating the need for surgical removal after implantation. Bioresorbable materials are biocompatible, ensuring they do not elicit adverse immune responses during their degradation process.

[0073] The term "biocompatible" as used herein refers to a material that is generally non-toxic to the recipient and does not possess any significant untoward effects to the subject and, further, that any metabolites or degradation products of the material are non-toxic to the subject. Typically, a substance that is "biocompatible" causes no clinically relevant tissue irritation, injury, toxic reaction, or immunological reaction to living tissue.

[0074] The term "biodegradable" as used herein refers to a material that will erode to soluble species or that will degrade under physiologic conditions to smaller units or chemical species that are, themselves, non-toxic (biocompatible) to the subject and capable of being metabolized, eliminated, or excreted by the subject.

[0075] The term "sphericity" as used in the present description, should also be understood as being similar to "ovality", "roundness", "regularity", or "circularity". The sphericity (SP) may be defined as the ratio of the diameter of an area equivalent circle to the diameter of the circumscribing circle. The circularity (CR) may be defined as the ratio of the particle's area to the area of a perimeter equivalent circle, and may be measured according to ASTM F1877-16.

[0076] The term "non-agglomerating" as used herein refers to the powder when it does not generate large clumps of material.

[0077] The term "improved flowability" as used herein refers to the fluidization of powder particulates through movement generated by various stimuli to include impact forces from falling, dynamic powder flow analysis, and especially spreading by blade, roller, or feeding mechanism during processing.

[0078] In the following passages, different aspects or embodiments of the invention are defined in more detail. Each aspect or embodiment so defined may be combined with any other aspect(s) or embodiment(s) unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0079] According to a first aspect, the present invention provides a process for producing a powder for additive manufacturing. The process preferably comprises the steps of a) providing a powder comprising polyester particles, preferably polycaprolactone particles; b) subjecting the powder comprising polyester particles to thermal spheroidization by heating said powder above the peak melting temperature of the polyester particles and subsequently cooling the powder, thereby obtaining a powder comprising spherical polyester particles; and, c) annealing the powder comprising spherical polyester particles, thereby obtaining the powder for additive manufacturing.

[0080] It has been found herein that the present process is particularly suitable for producing stable and free- flowing powders for additive manufacturing, preferably additive manufacturing comprising any suitable powder bed fusion techniques. The terms "powder bed fusion" and "powder bed fusing" as used herein interchangeably intend to refer to additive manufacturing processes wherein a powder is selectively sintered or melted and fused, layer-by-layer to provide a three-dimensional object such as an article or (medical) device. Powder bed fusion as disclosed herein further includes all laser sintering and all selective laser sintering processes as well as other powder bed fusing technologies, such as selective heat sintering, and other processes as defined by ASTM F2792-12a.

[0081] An advantage of the present process is that arbitrarily-shaped polyester particles may be shaped into spherical, non-agglomerating polyester particles without the need for solvents or additives, which typically have an adverse effect on production costs and / or regulatory compliance (e.g., biocompatibility).

[0082] In what follows below, particularities and properties of the present process, starting materials applied therein, and resulting products and intermediates will be discussed in greater detail.

[0083] The term "powder" as used herein generally refers to a collection of fine, solid particles suitable as a feedstock in additive manufacturing processes. In the context of the present invention, the produced additive manufacturing powder comprises polyester particles of a defined shape and composition.

[0084] In some embodiments, the present powder comprises or consists (essentially) of polyester particles. In some embodiments the powder comprises at least 60 wt.% of polyester particles, or at least 70 wt.%, or at least 75 wt.%, or at least 80 wt.%, or at least 85 wt.%, preferably at least 90 wt.%, or at least 95 wt.%, or at least 96 wt.%, or at least 97 wt.%, or at least 98 wt.%, or at least 99 wt.% of polyester particles. The polyester particles described herein may be any biocompatible polyester. Biocompatible polyesters include but are not limited to polycaprolactone, polylactide, polyglycolide, polydioxanone, polyhydroxybutyrate, polyhydroxyvalerate, and copolymers thereof and / or mixtures thereof. The term copolymers used in said context refers to copolymers of the respective monomers of the biocompatible polyesters, such as poly(lactide-co-glycolide), poly(lactide-co-caprolactone), as well as copolymers containing a poly(lactide-co-caprolactone), polyhydroxybutyrate, and polyhydroxyvalerate.

[0085] Lactide-based polymers can comprise any lactide residue, including all racemic and stereospecific forms of lactide, including, but not limited to, L-lactide, D-lactide, and D,L-lactide, or a mixture thereof. Useful polymers comprising lactide include, but are not limited to poly(L-lactide), poly(D-lactide), and poly(D, L-lactide); and poly(lactide-co-glycolide), including poly(L-lactide-co-glycolide), poly(D-lactide- co-glycolide), and poly(D,L-lactide-co-glycolide); or copolymers, terpolymers, combinations, or blends thereof. Lactide / glycolide polymers can be conveniently made by melt polymerization through ring opening of lactide and glycolide monomers. Additionally, racemic D, L-lactide, L-lactide, and D-lactide polymers are commercially available. The L-polymers are more crystalline and resorb slower than DL polymers. In addition to copolymers comprising glycolide and D, L-lactide or L-lactide, copolymers of L-lactide and D, L-lactide are commercially available. Homopolymers of lactide or glycolide are also commercially available.

[0086] Preferably, the present polyester particles are polycaprolactone particles. Polycaprolactone may offer several advantages as a bioresorbable polymer, making said polyester especially useful for medical applications. For instance, in some embodiments, printed articles or devices made from the present powder comprising spherical polycaprolactone particles may be characterized by an extended resorption time (e.g., lasting months to years), making it suitable for applications that require longterm support, such as in implants or tissue scaffolds.

[0087] In a first step of the present process, an initial powder comprising polyester particles of irregular shape is provided. In other words, the initial powder comprises a collection of solid polyester particles, wherein the individual particles do not exhibit a uniform or consistent geometric form. The irregular polyester particles may comprise particles having uneven or non-symmetrical shapes, which may include angular, jagged, elongated, or faceted features.

[0088] Polyester particles, and in particular polycaprolactone particles, are typically irregular in shape due to the manufacturing processes used to produce them, as well as the inherent properties of the material itself. For instance, during production of polyester, polymer strands or bulk materials are ground, milled, or otherwise mechanically fragmented into powder form. These mechanical methods typically do not create uniform particles. In addition, polyesters are relatively brittle polymer materials, which may cause the material to fracture in a less controlled, uneven manner during grinding or milling processes.

[0089] In some preferred embodiments, the step of providing the powder comprising (irregular) polyester particles, preferably (irregular) polycaprolactone particles, comprises grinding polyester material (e.g., polyester pellets, such as polycaprolactone pellets) into a powder. Grinding may involve cryogenic grinding, also known as cryogenic milling, freezer milling, freezer grinding, or cryomilling. Cryogenic grinding typically comprises cooling the polyester material, e.g., using liquid nitrogen or carbon dioxide, to embrittle the material before subjecting it to mechanical grinding or milling.

[0090] In a second step of the present process, the powder comprising irregular polyester particles is shaped into a powder comprising spherical polyester particles. More specifically, the present inventors have found that thermal spheroidization of the irregularly shaped particles, relying on controlled melting of said non-uniform particles, may advantageously provide highly spherical polyester particles with a desirable shape, size, and / or size distribution for additive manufacturing.

[0091] Thermal spheroidization as described herein involves heating the polyester particles to a temperature near or above their melting point to transform into particles of spherical or near-spherical shapes.

[0092] Suitable conditions for thermal spheroidization include using high-temperature thermal sources such as plasma, flame, or laser heating, where the particles are exposed to a controlled heat environment. Controlled melting of the irregular polyester particles may be effected by dispersing the particles in a suitable medium such that heat emitted by a thermal source may be absorbed to (partially) melt the polyester particles while being suspended in the medium.

[0093] In some embodiments, the medium is a liquid that is immiscible with molten polyester, such as an oil. In such embodiments, the polyester particles may be brought into suspension in the liquid medium. The liquid medium is then heated to above the melting temperature of the polyester particles, thus (partially) melting the particles and leading to spontaneous spheroidization, driven by the molten material's surface tension. Next, the suspension is quenched, and the solidified particles are retrieved from the medium. Care must be taken to leave as little residue of the liquid medium as possible on the resulting spheroidized polyester particles.

[0094] In some preferred embodiments, the medium is a gas. In such embodiments, the particles of the powder comprising irregular polyester particles brought into suspension in a carrier gas. The powder is then heated by means of radiation generated by a radiation source, thus (partially) melting the particles and leading to spheroidization of the particles.

[0095] In an exemplary embodiment, step b) of the present process may comprise introducing the powder comprising irregular polyester particles in a carrier gas into a device that ensures the breakdown of agglomerates of said powder. In a subsequent step, the powder may be transported through a nozzle to a flow chamber located in a radiation area where radiation is generated by a radiation source, then the powder may absorb the radiation which leads to its (complete) melting or another thermal transition (e.g., a glass transition). The melted polyester particles may be removed from the radiation area by being carried in a carrier gas; while being carried by the gas stream, spheroidization of the liquid polymer occurs. Subsequently, the polymer may be allowed to (re)crystallize in the gas in a controlled crystallization chamber.

[0096] The term "carrier gas" as used herein has a well-established meaning within the art and is used herein as such. Carrier gas means a gas or gas mixture that serves to transport a sample or material through a system without substantially reacting with said sample or material. A suitable carrier gas may be air, nitrogen, argon, helium, carbon dioxide, sulphur hexafluoride, or mixtures thereof.

[0097] A suitable radiation source may be a laser.

[0098] In the context of the present invention, the spherical polyester particles, preferably spherical polycaprolactone particles, may further be subjected to an annealing step to improve the processability and stability of the resulting powder.

[0099] The term "annealing" as used herein generally refers to a heat treatment process in which the spherical polyester particles are heated to a specific temperature and held at that temperature for a defined period, followed by (controlled) cooling. It has been found herein that annealing of the spherical polyester particles may advantageously improve the flowability of the resulting powder and simultaneously reduce or avoid agglomeration of the spherical polyester particles.

[0100] In some preferred embodiments, annealing the powder, comprising spherical polyester particles, comprises heating said powder to a temperature between the recrystallization temperature and peak melting temperature of the spherical polyester particles. The "peak melting temperature" (Tm) corresponds to the temperature at which the spherical polyester particles undergo a phase transition from solid to liquid material. The "recrystallization temperature" (Tc) corresponds to the temperature at which the liquid, molten polyester material begins to recrystallize upon cooling. In other words, annealing may comprise heating the spherical polyester particles to a temperature wherein the polymer chains become more mobile and gain more freedom to move and flow, which allows to rearrange the polymer structure.

[0101] The precise temperature, duration, and cooling rate in the present annealing step may depend on the composition of the spherical polyester particles as is apparent to the person skilled in the art. For instance, the skilled person is aware that the peak melting temperature and / or recrystallization temperature of polycaprolactone may differ from poly(L-lactide).

[0102] Preferably, the present spherical polyester particles are spherical polycaprolactone particles having a Tmof about 50°C to about 70°C, or about 55°C to about 70°C, or about 55 °C to about 65°C, and a Tcranging from 30°C to 45°C, or from 30°C to 40°C.

[0103] In some preferred embodiments, the powder comprising spherical polyester particles is heated to a temperature between 5°C above the Tcand 1°C below the Tmof the spherical polyester particles, or between 6°C above the Tcand 1°C below the Tm, or between 6°C above the Tcand 2°C below the Tm, or between 7°C above the Tcand 2°C below the Tm, or between 7°C above the Tcand 3°C below the Tm, or between 7°C above the Tcand 4°C below the Tmof the spherical polyester particles.

[0104] In some embodiments, the powder comprising spherical polyester particles is heated to a temperature between 5% above the Tcand 1% below the Tmof the spherical polyester particles, or between 6% above the Tcand 1% below the Tm, or between 7% above the Tcand 1% below the Tm, or between 8% above the Tcand 1% below the Tm, or between 8% above the Tcand 2% below the Tm, or between 9% above the Tcand 2% below the Tm, or between 10% above the Tcand 2% below the Tm, or between 10% above the Tcand 3% below the Tm, or between 10% above the Tcand 4% below the Tm, or between 10% above the Tcand 5% below the Tm, of the spherical polyester particles, with Tcand Tmexpressed in °C.

[0105] Thermal transitions of polyesters, including peak melting temperatures, recrystallization temperatures, and other thermal properties, may be determined by means of widely used techniques such as differential scanning calorimetry (DSC). During the heating phase of a DSC scan, the energy required to melt the crystalline regions of the polyester is recorded, and the peak of the resulting endothermic curve represents the peak melting temperature. The recrystallization temperature may be measured during the cooling phase of a DSC scan, after the polyester has been melted. As the material cools, the exothermic peak represents the temperature at which the polymer chains begin to recrystallize. Suitable DSC equipment include a TA instruments Q2000 DSC operated at a heating and cooling rate of 10°C / min (under nitrogen atmosphere) and using an indium calibration standard. In some preferred embodiments, annealing the powder, comprising spherical polyester particles, comprises heating said powder to a temperature between the recrystallization temperature and peak melting temperature of the spherical polyester particles for a period of at least 5 hours, or at least 6 hours, or at least 7 hours, or at least 8 hours, or at least 9 hours, or at least 10 hours, or at least 11 hours, or at least 12 hours, or from at least 12 hours to at most 7 days.

[0106] After heating the powder comprising spherical polyester particles at the specified temperatures and periods above, the polyester may subsequently be cooled. Cooling in the present context may comprise active cooling, allowing to cool in a controlled manner, and / or allowing to cool in an uncontrolled manner. For instance, the polyester may be actively cooled to a first temperature and subsequently allowed to further cool in a controlled or uncontrolled manner to a second temperature, wherein the second temperature is lower than the first temperature.

[0107] In "active cooling", external mechanisms or systems may be used to allow the polyester to solidify more quickly. For instance, cold water, chilled air, a cold surface, as well as cryogenic methods may be used to cool the polyester particles. In "controlled cooling", the polymer is allowed to cool at a gradual, uniform rate under (more) carefully regulated conditions. This is achieved by controlling the cooling medium, such as air or water, such that the cooling rate may be optimized. For example, programmable cooling systems may be used to regulate temperature more precisely over time. This may involve stepwise cooling profiles. Uncontrolled cooling occurs when the polymer is allowed to cool naturally in ambient conditions without any deliberate attempt to control the cooling rate or temperature gradient.

[0108] In some preferred embodiments, annealing the powder comprising spherical polyester particles comprises heating said powder to a temperature between the recrystallization temperature and peak melting temperature of the spherical polyester particles for at least 5 hours and subsequently cooling the powder.

[0109] In some embodiments, the step of subsequently cooling the powder comprising spherical polyester particles when annealing said powder comprises cooling to a temperature of between 20°C and 25°C.

[0110] In some embodiments, the step of subsequently cooling the powder comprising spherical polyester particles when annealing said powder comprises cooling to a temperature of between 20°C and 25°C over a period of at least 1 hour, or at least 2 hours, or at least 3 hours, or at least 4 hours, or at least 5 hours, or at least 6 hours, or at least 7 hours, or at least 8 hours, or at least 9 hours, or at least 10 hours, or at least 11 hours, or at least 12 hours, or from at least 1 hour to at most 7 days. In some preferred embodiments, the step of subsequently cooling the powder comprising spherical polyester particles when annealing said powder comprises cooling to a temperature of between 20°C and 25°C at a cooling rate of between 0.1°C / min and 5.0°C / min, or between 0.1°C / min and 4.5°C / min, or between 0.1°C / min and 4.0°C / min, or between 0.1°C / min and 3.5°C / min, or between 0.1°C / min and 3.0°C / min, or between 0.1°C / min and 2.5°C / min, or between 0.1°C / min and 2.0°C / min, or between 0.1°C / min and 1.5°C / min, or between 0.1°C / min and 1.0°C / min, or between 0.1°C / min and 0.9°C / min, or between 0.2°C / min and 0.9°C / min, or between 0.2°C / min and 0.8°C / min.

[0111] In some preferred embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with an average particle size of from at least 10.0 pm to at most 150.0 pm, or at least 20.0 pm to at most 150.0 pm, or at least 30.0 pm to at most 150.0 pm, or at least 40.0 pm to at most 150.0 pm, or at least 40.0 pm to at most 140.0 pm, or at least 40.0 pm to at most 130.0 pm, or at least 40.0 pm to at most 120.0 pm, or at least 40.0 pm to at most 110.0 pm, or at least 40.0 pm to at most 100.0 pm, or at least 50.0 pm to at most 100.0 pm. The average particle size of the spherical polyester particles comprised in the produced powder may be determined by means of static image analysis according to the ISO 13322-1 / 2014 standard. The particle size distribution may be determined using a static image analysis instrument (e.g. Occhio 500 NanoXY equipped with a pneumatic dry dispersing unit). The static image analysis method for determining particle size distribution may involve preparing a sample to ensure well-dispersed particles, capturing high-resolution images using a microscope equipped with a camera, and processing said images using dedicated software. The software converts images to binary format, segments individual particles, and measures parameters such as diameter, perimeter, area, and shape.

[0112] In some preferred embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with a circularity of greater than 0.80, or greater than 0.85, or greater than 0.86, or greater than 0.87, or greater than 0.88, or greater than 0.89, or greater than 0.90. The circularity of the spherical polyester particles comprised in the produced powder may be determined by means of static image analysis as described above.

[0113] In some preferred embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with an elongation of greater than 0.80, or greater than 0.85, or greater than 0.86, or greater than 0.87, or greater than 0.88, or greater than 0.89, or greater than 0.90. The elongation of the spherical polyester particles comprised in the produced powder may be determined by means of static image analysis as described above. The elongation (EG) may be defined as the ratio of the semi-minor axis length ( Rmin) to the semi-major axis length (Rmax).

[0114] In some embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with a roundness of greater than 0.80, or greater than 0.85, or greater than 0.86, or greater than 0.87, or greater than 0.88, or greater than 0.89, or greater than 0.90. The roundness of the spherical polyester particles comprised in the produced powder may be determined by means of static image analysis as described above.

[0115] In some embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with an aspect ratio of greater than 0.80, or greater than 0.85, or greater than 0.86, or greater than 0.87, or greater than 0.88, or greater than 0.89, or greater than 0.90. The aspect ratio of the spherical polyester particles comprised in the produced powder may be determined by means of static image analysis as described above. The aspect ratio (AR) may be defined as the ratio of the minimum Feret diameter to the maximum Feret diameter, and may be measured according to ASTM F1877 or ISO 9276-6. The Feret diameter may be defined as the distance between the two parallel planes restricting the object perpendicular to that direction.

[0116] In some embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with a convexity of greater than 0.80, or greater than 0.85, or greater than 0.86, or greater than 0.87, or greater than 0.88, or greater than 0.89, or greater than 0.90. The convexity of the spherical polyester particles comprised in the produced powder may be determined by means of static image analysis as described above. The convexity may be defined as the ratio of the surface area of a particle to the surrounding convex hull.

[0117] In some embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with an average particle size of from at least 10.0 pm to at most 150.0 pm; a circularity of greater than 0.80; and, an aspect ratio of greater than 0.80.

[0118] In some embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with an average particle size of from at least 10.0 pm to at most 150.0 pm; a circularity of greater than 0.85; and, an aspect ratio of greater than 0.80.

[0119] In some embodiments, the powder for additive manufacturing comprises greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of spherical polyester particles with an average particle size of from at least 50.0 pm to at most 100.0 pm; a circularity of greater than 0.90; and, an aspect ratio of greater than 0.90.

[0120] In some embodiments, the powder for additive manufacturing comprises spherical polyester particles with a particle size distribution D50 of less than 100.0 pm; and greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polyester particles have a circularity of greater than 0.80; and, an aspect ratio of greater than 0.80.

[0121] In some embodiments, the powder for additive manufacturing comprises spherical polyester particles with a particle size distribution D50 of between 60.0 pm and 90.0 pm; and greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polyester particles have a circularity of greater than 0.90; and, an aspect ratio of greater than 0.90.

[0122] In some embodiments, the powder for additive manufacturing comprises spherical polyester particles with a particle size distribution D10 of between 35.0 pm and 60.0 pm, or between 35.0 pm and 55.0 pm, 35.0 pm and 50.0 pm, or between 40.0 pm and 50.0 pm.

[0123] In some preferred embodiments, the powder for additive manufacturing comprises spherical polyester particles with a particle size distribution D50 of between 40.0 pm and 100.0 pm, or between 45.0 pm and 100.0 pm, or between 50.0 pm and 100.0 pm, or between 55.0 pm and 100.0 pm, or between 60.0 pm and 100.0 pm, or less than 100.0 pm, or between 60.0 pm and 95.0 pm, or less than 95.0 pm, or between 60.0 pm and 90.0 pm, or between 65.0 pm and 90.0 pm.

[0124] In some preferred embodiments, the powder for additive manufacturing comprises spherical polyester particles with a particle size distribution D90 of less than 150.0 pm, or less than 140.0 pm, or less than 130.0 pm, or less than 120.0 pm, or between 65.0 pm and 150.0 pm, or between 70.0 pm and 150.0 pm, or between 75.0 pm and 150.0 pm, or between 80.0 pm and 150.0 pm, or between 85.0 pm and 150.0 pm, or between 90.0 pm and 150.0 pm, or between 95.0 pm and 150.0 pm, or between 100.0 pm and 150.0 pm, or between 100.0 pm and 140.0 pm, or between 100.0 pm and 130.0 pm.

[0125] As used herein, D50 (as known as "volume median diameter" or "average particle diameter by volume") refers to the particle diameter of the powder where 50 vol. % of the particles in the total distribution of the referenced sample have the noted particle diameter or smaller. Similarly, D10 refers to the particle diameter of the powder where 10 vol. % of the particles in the total distribution of the referenced sample have the noted particle diameter or smaller; and D90 refers to the particle diameter of the powder where 90 vol. % of the particles in the total distribution of the referenced sample have the noted particle diameter or smaller. The D10, D50, and D90 particle size distribution of the produced spherical polyester particles may be determined by means of static image analysis as described above.

[0126] In some preferred embodiments, the produced additive manufacturing powder is free or essentially free from any flow aids and / or calcium phosphates, such as hydroxyapatite.

[0127] In some embodiments, the produced additive manufacturing powder comprises at most 1.0 wt.% of flow aids and / or calcium phosphates, such as hydroxyapatite, or at most 0.5 wt.%, or at most 0.1 wt.%, or at most 0.05 wt.%, or at most 0.01 wt.%, or at most 0.005 wt.%, or at most 0.001 wt.% of flow aids and / or calcium phosphates, such as hydroxyapatite; with wt.% relative to the total weight of the powder.

[0128] In some embodiments, the powder has a bulk density equal to or greater than 0.564 g / cm3, or between 0.500 and 0.600 g / cm3. The bulk density may be measured using a tapped density analyser (e.g. GranuTools GranuPack). This measurement evaluates the flowability and packing properties of powders by determining the tapped density through controlled tapping, assessing compaction kinetics by recording density changes over successive taps. In some embodiments, the powder has a packing density equal to or greater than 0.689 g / cm3, or between 0.600 and 0.800 g / cm3. The packing density may be measured using a tapped density analyser (e.g. GranuTools GranuPack). This measurement evaluates the flowability and packing properties of powders by determining the tapped density through controlled tapping, assessing compaction kinetics by recording density changes over successive taps.

[0129] It has been found that the present powder is characterized by improved consistency in thermal behaviour, which allows for better control over the flowability and spreading of the powder during additive manufacturing.

[0130] In some embodiments, the powder has an enthalpy of melting of at least 50 J / g, or at least 55 J / g, or at least 60 J / g.

[0131] In some preferred embodiments, the powder for additive manufacturing has a cohesive index of equal to or less than 20, or less than 19, or less than 18, or less than 17, or less than 16, or less than 15. The cohesive index is a parameter used to evaluate the flowability of powders, particularly in the context of Powder Bed Fusion (PBF) processes. It provides an indication of the extent to which particles in a powder adhere to each other, affecting their ability to flow smoothly. The determination of the cohesive index may be performed using a rotating drum analysis instrument (e.g. GranuTools GranuDrum). The rotating drum measurement determines the cohesive index by loading a powder sample into a transparent cylindrical drum, rotating it at a controlled speed, and observing the powder's behaviour. The cohesive index can be calculated based on these observations: higher avalanche frequency indicates lower cohesion, while more significant clumping and steeper angles of repose suggest higher cohesion.

[0132] In some embodiments, the powder for additive manufacturing has a Hausner ratio equal to or less than 1.25, or between 1.00 and 1.25. The Hausner ratio may be measured using a tapped density analyser (e.g. GranuTools GranuPack). This measurement evaluates the flowability and packing properties of powders by determining the tapped density through controlled tapping, assessing compaction kinetics by recording density changes over successive taps, and calculating the Hausner Ratio and Compressibility Index from the initial bulk density and tapped density.

[0133] In some embodiments, the powder for additive manufacturing has a Carr index equal to or less than 20%, or between 10% and 20%. The Carr index may be measured using a tapped density analyser (e.g. GranuTools GranuPack). This measurement evaluates the flowability and packing properties of powders by determining the tapped density through controlled tapping, assessing compaction kinetics by recording density changes over successive taps, and calculating the Hausner Ratio and Compressibility Index from the initial bulk density and tapped density.

[0134] As mentioned above, the present powder is particularly effective for use in additive manufacturing, preferably additive manufacturing comprising powder bed fusion techniques.

[0135] The present invention further encompasses the powder obtained or obtainable by means of the process according to the first aspect of the present invention or (preferred) embodiments thereof.

[0136] A second aspect of the present invention relates to a powder for additive manufacturing, the powder comprising spherical polyester particles, preferably polycaprolactone particles, wherein greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polyester particles have an average particle size of from at least 10.0 pm to at most 150.0 pm; and a circularity of greater than 0.80.

[0137] It should be clear that (preferred) embodiments of the process according to a first aspect of the invention and associated advantages thereof are also (preferred) embodiments of the powder according to a second aspect of the invention and vice versa.

[0138] In preferred embodiments, the powder comprises spherical polyester particles, wherein greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polyester particles have an average particle size of from at least 10.0 pm to at most 150.0 pm; and a circularity of greater than 0.85; and preferably an aspect ratio of greater than 0.75. In preferred embodiments, the powder comprises spherical polyester particles, wherein greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polyester particles have an average particle size of from at least 10.0 pm to at most 150.0 pm; and a circularity of greater than 0.85; and preferably a sphericity of greater than 0.85, and an aspect ratio of greater than 0.75.

[0139] In exemplary embodiments, the present powder comprises spherical polycaprolactone particles, wherein greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polycaprolactone particles have an average particle size of from at least 50.0 pm to at most 150.0 pm; a circularity of greater than 0.80; and a particle size distribution D50 of between 60.0 pm and 90.0 pm.

[0140] In exemplary embodiments, the present powder comprises spherical polycaprolactone particles, wherein greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polycaprolactone particles have an average particle size of from at least 50.0 pm to at most 150.0 pm; a circularity of greater than 0.85; and a particle size distribution D50 of between 60.0 pm and 90.0 pm.

[0141] In exemplary embodiments, the present powder comprises spherical polycaprolactone particles, wherein greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polycaprolactone particles have an average particle size of from at least 50.0 pm to at most 150.0 pm; a circularity of greater than 0.80; a particle size distribution D50 of between 60.0 pm and 90.0 pm; and an elongation of greater than 0.80.

[0142] In exemplary embodiments, the present powder comprises spherical polycaprolactone particles, wherein greater than 50 vol.% (preferably greater than 60 vol.%, preferably greater than 70 vol.%, preferably greater than 80 vol.%, preferably greater than 90%) of the spherical polycaprolactone particles have an average particle size of from at least 50.0 pm to at most 150.0 pm; a circularity of greater than 0.85; a particle size distribution D50 of between 60.0 pm and 90.0 pm; and a sphericity of greater than 0.85.

[0143] A third aspect of the present invention relates to an additive manufacturing process. The process preferably comprises the steps of: i) providing the powder obtained or obtainable by means of the process according to a first aspect of the present invention or (preferred) embodiments thereof; or the powder according to the second aspect of the present invention or (preferred) embodiments thereof; and, ii) selectively melting or sintering the powder, thereby obtaining a printed article or device.

[0144] The process may also comprise the steps of: i') providing a powder comprising polyester particles, preferably polycaprolactone particles; i") subjecting the powder comprising polyester particles to thermal spheroidization by heating said powder above the peak melting temperature of the polyester particles and subsequently cooling the powder, thereby obtaining a powder comprising spherical polyester particles; annealing the powder comprising spherical polyester particles; and, ii) selectively melting or sintering the annealed powder, thereby obtaining a printed article or device.

[0145] It should be clear that (preferred) embodiments of the first aspect of the invention, the second aspect of the invention and associated advantages thereof are also (preferred) embodiments of the third aspect of the invention and vice versa.

[0146] The present additive manufacturing process may comprise any suitable powder bed fusion (PBF) process, including laser sintering processes such as selective laser sintering or selective heat sintering. Laser sintering processes are known and are based on the selective melting or sintering of particles, where layers of particles are exposed to laser energy and thus bonded to one another. Successive sintering of layers of particles produces three-dimensional objects.

[0147] Selective laser sintering (SLS) uses a high-power laser (typically a CO2or fibre laser) to selectively fuse powdered material layer by layer. Key steps of selective laser sintering may include spreading a thin layer of powder over a build platform, and scanning the powder surface with a laser such that the polyester particles comprised in said powder heat and fuse together according to a three-dimensional (3D) design. This process is repeated layer-by-layer until an object of a desired 3D shape is built. Digital data representative of the desired 3D shape for the object is typically loaded into the selective laser sintering machine from a file, a database, or any other suitable data storage. The data comprises, for each layer, information describing the cross section of the object at that layer, also referred to as slice. For each slice of the object, the machine deposits a thin layer of fresh powder onto a part bed within a build chamber using a roller or blade system and subsequently locally heats up the powder particles, e.g., by directing a CO2laser beam to locations in the deposited top layer in the part bed corresponding to locations within the object's respective slice, to selectively bond, e.g., sinter, fuse or melt, them together and to adhere them to the previously bonded slices of lower layers. Details concerning selective laser sintering can be found, by way of example, in the specification of WO88 / 02677A2, the entire contents of each of which are incorporated herein by reference.

[0148] Selective heat sintering (SHS) is a processing technique similar to selective laser sintering but uses a heated thermal printhead (instead of a laser) to fuse powdered thermoplastic material. The printhead selectively applies heat to sinter the powder layer by layer.

[0149] Suitable PBF equipment, such as SLS equipment or SHS equipment, for additive manufacturing of the present powder comprising spherical, non-agglomerating polyester particles, preferably polycaprolactone particles, utilizes a local energy source, such as a high-power laser or a printhead, to selectively sinter powdered materials layer by layer based on digital design data, forming the final object. Operation of the equipment may proceed as follows. A thin layer of powder comprising spherical polyester particles is spread across a movable build platform by a roller or blade system. The thickness of the layer may be determined by the type of polyester material and the resolution required for the final object. A control unit may direct a laser or a printhead to selectively sinter the powder by scanning specific areas based on digital design data. The laser or printhead fuses the powder particles together, forming a solid layer. Unsintered powder surrounding the fused areas remains loose and may serve as a support for subsequent layers. After the first layer is sintered, the build platform can be lowered by a predefined layer thickness (e.g., 100 pm), and a new layer of powder is spread over the previously sintered layer. This process is repeated until the entire object is built.

[0150] To facilitate the deposition of a new layer of powder by the roller or blade system, it is important that the powder exhibits an almost free-flowing behaviour. Powder with low flowability may lead to agglomeration of powder particles during deposition, and therefore an uneven layer of new powder. Advantageously, it has surprisingly been found that the present additive manufacturing process allows to circumvent these disadvantages.

[0151] The PBF equipment may further comprise a suitable build chamber, which is a sealed environment in which the powder bed and the object can be formed. The build chamber may be maintained under controlled temperature and atmosphere to ensure optimal sintering conditions.

[0152] It should be clear that typically care should be taken to strictly control the temperature of the manufacturing equipment, e.g., maintain the temperature of the build chamber within a particular temperature range, to avoid bonding of particles outside targeted locations and simultaneously provide good adhesion among freshly bonded layers. Working outside this temperature range may cause curling, a distortion of the object being manufactured where the outer edges warp upwards. This reduces the dimensional accuracy of the manufacturing process since the 3D shape of the physical object will deviate from the desired 3D shape. In addition, this could lead to print failures and, consequently, increased scrap rates. In contrast, it has been found herein that the present powder, comprising spherical, non-agglomerating polyester particles— preferably polycaprolactone particles— can be advantageously processed under less stringent temperature conditions as demonstrated in the example section.

[0153] According to a fourth aspect, the present invention further encompasses all three-dimensional objects made by additive manufacturing of the powder according to the third aspect of the present invention or (preferred) embodiments thereof. After a layer-by-layer manufacture of an object, the object may 1 exhibit excellent resolution, durability, and strength. Such objects may include various articles and / or devices that may have a wide variety of uses, including uses as prototypes, as well as end products.

[0154] Articles or devices in the context of the present additive manufacturing process can be any products for which additive manufacturing makes sense, such as individualized products or products with highly complex shapes that are difficult or impossible to manufacture with more traditional manufacturing technologies (e.g., manifolds, lattice structures, products with integrated functional parts, such as hinges).

[0155] Devices can be medical devices, such as (parts of) medical instruments or implantable medical devices. Medical devices can be individualized medical devices, such as patient-specific medical devices, e.g., (parts of) medical instruments or implantable medical devices of which at least part of their 3D shape has been customized to fit onto part of an individual patient's anatomy and / or to accomplish an envisaged result of a patient-specific pre-operative plan (e.g., by guiding certain surgical steps in a pre- operatively determined way, by replacing missing anatomical parts with a prosthetic of a pre- operatively determined shape, by fixating bone fragments in a pre-operatively determined spatial relationship to each other).

[0156] Implantable medical devices can be bioresorbable implantable medical devices. These are devices configured to be absorbed in the patient's body over a period of time from implantation, of several weeks, months or years. In many cases, bioresorbable implantable medical devices serve a temporary purpose, such as drug delivery, fixation or providing support for certain anatomical structures as they grow or heal. Examples include, but are not limited to, bone fixation systems, such as plates and screws, splints, such as tracheal splints, drug delivery devices, tissue-regeneration scaffolds, and breast implants. Bioresorbable breast implants may comprise open - e.g., scaffold-like or lattice-like - structures that temporarily create a cavity or act as a support structure for new breast tissue to grow into. Bioresorbable breast implants may be used in cosmetic or oncological surgery. They may serve in full (e.g., mastectomy) or partial (e.g., lumpectomy) breast surgery. They may even promote tissue growth or act as tissue regeneration scaffolds.

[0157] Obtaining a design of the device to be manufactured may comprise obtaining digital data representative of a 3D shape of the device, using a computing device. The digital data may be in any format suitable for loading the data into an additive manufacturing machine, such as STL, SLC, OBJ, GCODE, VRML, CNC, and the like. The digital data may be loaded from a data file, database, or any other data storage medium. Additionally or alternatively, e.g., in embodiments where the device to be manufactured is an individualized product, such as an individualized medical device, more specifically a patient-specific device, the step of obtaining a design of the device may comprise using a computing device to generate a digital design in three dimensions for a shape of the device to be manufactured, such as by using a computer-aided-design software application (e.g., 3-matic by Materialise, Belgium). In the case of patient-specific medical devices, generating said digital design may comprise accessing medical image data of part of a patient's anatomy and basing the digital design on the medical image data. Additionally or alternatively, generating said digital design may comprise accessing a virtual 3D model of part of a patient's anatomy and basing the digital design on the virtual 3D model. Additionally or alternatively, generating said digital design may comprise accessing medical image data of part of a patient's anatomy, generating a virtual 3D model of the part of the patient's anatomy based on the medical image data, and basing the digital design on the virtual 3D model.

[0158] In some preferred embodiments, the device is a bioresorbable implant, preferably a breast implant, splint, stent, tissue-regeneration scaffold, drug-delivery device, or fixation device.

[0159] According to a fifth aspect, the present invention relates to the use of the powder according to a second aspect of the present invention or (preferred) embodiments thereof, or obtained or obtainable by means of the process according to a first aspect of the present invention or (preferred) embodiments thereof, in an additive manufacturing process, preferably an additive manufacturing process comprising powder bed fusion.

[0160] It should be clear that (preferred) embodiments of the first aspect of the invention, the second aspect of the invention, the third aspect of the invention, the fourth aspect of the invention, and associated advantages thereof are also (preferred) embodiments of the fifth aspect of the invention and vice versa.

[0161] The invention is illustrated but not limited by the following examples.

[0162] EXAMPLES

[0163] EXAMPLES

[0164] Example 1

[0165] In a first example, a powder comprising spherical polycaprolactone (PCL) particles was produced.

[0166] Step 1 - providing powder comprising irregular particles First, a powder comprising polycaprolactone particles with a D50 ranging between 40 pm to 70 pm was obtained.

[0167] The obtained material was subjected to size distribution analysis and shape analysis using a static image analysis method according to the ISO 13322-1 / 2014 standard. The material was characterized with a D10 of at least 30 pm, a D50 of at least 55 pm and a D90 of at least 90 pm. Greater than 50 volume percent of the powder particles had an aspect ratio greater than 0.68. Greater than 50 volume percent of the powder particles had an elongation greater than 0.43. Greater than 50 volume percent of the powder particles had a sphericity greater than 0.77. Greater than 50 volume percent of the powder particles had a circularity greater than 0.81.

[0168] The obtained material was subjected to tapped density analysis. The initial bulk density and packed density were determined to be 0.350 g / ml and 0.440 g / ml, respectively. The Hausner ratio and Carr index were calculated to be 1.26 and 20.35%, respectively.

[0169] Step 2 - thermal spheroidization

[0170] The obtained powder comprising irregular PCL particles was subjected to thermal spheroidization to obtain spherical polycaprolactone particles. The powder produced in step 1 was fed in air into a reactor. The powder was introduced into a transparent flow chamber made of borosilicate glass, with a circular cross-section, 35 mm in diameter, 1 mm wall thickness and 300 mm length at a rate of between 0.01 kg / h and 0.02 kg / h. A filament infrared emitter with a nominal power-to-irradiated-area ratio of 66 kW / m2and an aluminium reflection layer conformal with the surface of an optically transparent chamber on the side opposite to the radiation source, was used to reflect unabsorbed radiation back into the transparent chamber. The powder was introduced through a flat nozzle. Controlled crystallization was carried out in air at room temperature.

[0171] Step 3 - annealing

[0172] The obtained powder comprising spherical PCL particles was subsequently subjected to an annealing step. The powder was heated to a temperature of around 58°C, kept at said temperature for 13 hours to 67 hours (see Figures 4-5, respectively), and subsequently cooled to a temperature of around 20°C during a period of at least 2 hours.

[0173] The obtained material was subjected to size distribution analysis and shape analysis using a microscopic image analysis method according to the ISO 13322-1 / 2014 standard. The material was characterized with a D10 of at least 47 pm, a D50 of at least 79 pm and a D90 of at least 125 pm. Greater than 50 volume percent of the powder particles had an aspect ratio greater than 0.78. Greater than 50 volume percent of the powder particles had an elongation greater than 0.59. Greater than 50 volume percent of the powder particles had a sphericity greater than 0.84. Greater than 50 volume percent of the powder particles had a circularity greater than 0.85.

[0174] The obtained material was subjected to tapped density analysis. The initial bulk density and packed density were determined to be 0.564 g / ml and 0.689 g / ml, respectively. The Hausner ratio and Carr index were calculated to be 1.22 and 18.18%, respectively.

[0175] The obtained material was subjected to a flowability analysis using a rotating drum analysis instrument. The powder has a cohesive index of 18, indicating good flowability. The results indicate a reduction in particle agglomeration upon heating in the measurement cell.

[0176] Comparative Example 1

[0177] As a comparative example, a powder comprising spherical polycaprolactone (PCL) particles was produced without annealing said powder.

[0178] Step 1 - providing powder comprising irregular particles

[0179] First, a powder comprising polycaprolactone particles with a D50 ranging between 40 pm to 70 pm was obtained.

[0180] The obtained material was subjected to size distribution analysis and shape analysis using a static image analysis method according to the ISO 13322-1 / 2014 standard. The material was characterized with a D10 of at least 30 pm, a D50 of at least 55 pm and a D90 of at least 90 pm. Greater than 50 volume percent of the powder particles had an aspect ratio greater than 0.68. Greater than 50 volume percent of the powder particles had an elongation greater than 0.43. Greater than 50 volume percent of the powder particles had a sphericity greater than 0.77. Greater than 50 volume percent of the powder particles had a circularity greater than 0.81.

[0181] The obtained material was subjected to tapped density analysis. The initial bulk density and packed density were determined to be 0.350 g / ml and 0.440 g / ml, respectively. The Hausner ratio and Carr index were calculated to be 1.26 and 20.35%, respectively.

[0182] Step 2 - thermal spheroidization

[0183] The obtained powder comprising irregular PCL particles was subjected to thermal spheroidization to obtain spherical polycaprolactone particles. The powder produced in step 1 was fed in air into a reactor. The powder was introduced into a transparent flow chamber made of borosilicate glass, with a circular cross-section, 35 mm in diameter, 1 mm wall thickness and 300 mm length at a rate of between 0.01 kg / h and 0.02 kg / h. A filament infrared emitter with a nominal power-to-irradiated-area ratio of 66 kW / m2and an aluminium reflection layer conformal with the surface of an optically transparent chamber on the side opposite to the radiation source, was used to reflect unabsorbed radiation back into the transparent chamber. The powder was introduced through a flat nozzle. Controlled crystallization was carried out in air at room temperature.

[0184] The obtained material was subjected to a flowability analysis using a rotating drum analysis instrument. The cohesive index could not be determined due to agglomeration of the powder during analysis (see Figure 2 and 3 below).

[0185] Example 2

[0186] As demonstrated below, it has been found that the powder comprising spherical, non-agglomerating PCL particles of Example 1 exhibits different thermal and flowability characteristics compared with commercially available powder of comparative example 1.

[0187] As can be seen in Figure 1, the melting temperature of this spheroidized PCL powder is 59.8°C, but the melting peak in the heating curve is quite narrow, resulting in a wide theoretical processing window. However, the slight elevation in the heating curve between 40°C and 55°C indicates the presence of fractions in the powder with a lower melting temperature, which narrows the effective processing window and limits the suitability of this powder for powder-bed fusion. Moreover, experiments have shown that the powder of Figure 1 has poor flowability. Figure 2 shows an image taken during a rotating-drum flowability test at 45°C. As can be seen from the figure, the powder particles agglomerate to form large clumps. Figure 3 shows an image taken during a rotating-drum flowability test at 55°C. Similar agglomeration can be observed.

[0188] Figures 4-5 show the DSC thermograms of the powder of example 1 obtained after the annealing step.

[0189] In Figures 4 and 5, the spheroidized powder has undergone an annealing step at 58°C for 13 hours and 67 hours, respectively. Next, the powder has been left to gradually cool down to about 20°C. Finally, the powder has been sieved using a 125 pm sieve to break up any remaining clumps. As can be seen from Figures 4 and 5, the annealing step increases the melting temperature to 65.5°C and 68.5°C, respectively. Advantageously, both powders contain less fractions with a melting temperature below 60°C. Both powders therefore have a broader effective processing window. Moreover, rotatingdrum flowability experiments have shown that, after annealing, the spheroidized powder exhibits good flowability, evidenced by a cohesive index less than 18.

[0190] Example 3 In a third example, the powder obtained in example 1 was used for additive manufacturing.

[0191] Figures 6A-C show a build chamber of a selective-laser-sintering machine manufacturing a crossshaped object using the powder of example 1. Figure 6A shows a new layer of powder being deposited. Figure 6B shows the fresh layer of powder after deposition. The top layer has a very smooth surface, without the grooves and ridges as observed in Figure 7 with commercially available PCL-based powder. Figure 6C shows the top layer after the cross section of the object being manufactured has been scanned by a laser. No undesirable artefacts, such as curling, can be observed.

[0192] The broader effective processing window of this powder compared to commercially available PCL- based powder makes the present manufacturing process less dependent on the precise control of processing parameters.

[0193] Experiments have also shown that objects manufactured from powder of example 1 have a higher density than objects manufactured from commercially available powders that use a flow agent. The higher density may lead to higher mechanical strength.

[0194] Comparative Example 2

[0195] The sintering powder of comparative example 1 was used for additive manufacturing.

[0196] As described above, in relation to Figure 1, 2, and 3, the powder of comparative example 1 has the tendency to agglomerate during processing. As a result, printing proved impossible since the particles agglomerated so much that the additive manufacturing equipment was not able to deposit a new layer of powder.

[0197] Example 4

[0198] In a further example, the powder comprising spherical PCL particles obtained according to Example 1 was compared with a powder obtained by cryogenic milling of PCL (hereinafter "cryo-milled PCL") according to comparative example 1.

[0199] Both powders were subjected to particle size distribution and shape analysis in accordance with ISO 13322-1:2014. Figures 8A-C show the circularity (CR, Figure 8A), sphericity (SP, Figure 8B), and aspect ratio (AR, Figure 8C) of spherical PCL and cryo-milled PCL powders.

[0200] The results demonstrate that the spherical PCL powder exhibits a narrower particle size distribution compared with the cryo-milled powder, with the spherical particles showing a more uniform cumulative volume distribution. Advantageously, the results confirm that spherical PCL powder obtained by thermal spheroidization and annealing (as in Example 1) has superior shape characteristics and narrower particle size distribution than the comparative powder, leading to improved flowability and processability in additive manufacturing.

[0201] Example 5

[0202] A powder comprising spherical PCL particles obtainable according to Example 1 was used for further SLS-printing parameter development. The aim of this development was to compare the process window and the mechanical performance of parts printed from the powder according to the invention with parts printed from a comparative powder comprising non-spherical (cryo-milled) PCL particles.

[0203] The following SLS process parameters were considered during optimization:

[0204] Laser power (PLin W)

[0205] Laser scan speed (vsin mm s'1)

[0206] Laser scan spacing / hatch distance (h in mm)

[0207] Layer thickness (t) was fixed for all experiments in this example. These parameters define the volumetric energy density (Ev) (in J.mm-3) according to the relationship:

[0208] E .Plvvs■ h - 1

[0209] • Processing

[0210] During parameter development it could be observed that the comparative powder only allowed successful processing for relatively narrow Evvalues (approximately 60-70 J.mm-3). Attempts to use higher Evwith the comparative powder would lead to processing problems such as excessive curling of printed parts and failure to form defect-free specimens.

[0211] In contrast, the powder according to the invention could be processed successfully over a much broader range of Evvalues, including values well in excess of 150 J.mm-3.

[0212] • Mechanical testing

[0213] Tensile specimens printed from the spherical PCL powder could be prepared across a range of Evvalues and were tested in uniaxial tension. The printed part density and tensile failure behaviour were assessed. The key findings are:

[0214] At Evvalues below ~125 J.mm'3, printed specimens can typically exhibit relatively low part density and brittle failure behaviour (low break strain). • Upon increasing Evto and above a threshold of approximately 125 J.mrrr3, a change in failure behaviour could be observed: specimens can transition from brittle to ductile behaviour, evidenced by a significant increase in break strain (%). This transition is illustrated in Figures 9, 10A, 10B; and Figure 11. • Using re values in excess of 150 J.mrrr3can produce higher part densities and may allow further improvement in ductility, without the processing issues encountered for the comparative powder at similar energy levels.

[0215] This example demonstrates that powder according to the invention (produced by thermal spheroidization and annealing) can be processed in SLS over a substantially wider range of volumetric energy densities than prior art powders. The broader parameter window, together with improved packing density, flowability and spreadability, enables the fabrication of higher density parts with enhanced mechanical performance.

Claims

35CLAIMS1. A process for producing a powder for additive manufacturing, wherein the process comprises the steps of: a) providing a powder comprising irregular polyester particles; b) subjecting the powder comprising irregular polyester particles to thermal spheroidization by heating said powder above the peak melting temperature of the irregular polyester particles and subsequently cooling the powder, thereby obtaining a powder comprising spherical polyester particles; and, c) annealing the powder comprising spherical polyester particles, thereby obtaining the powder for additive manufacturing.

2. The process according claim 1, wherein the polyester is selected from the group comprising polycaprolactone, polylactide, polyglycolide, polydioxanone, polyhydroxybutyrate, polyhydroxyvalerate, and copolymers thereof and / or mixtures thereof; preferably wherein the polyester comprises polycaprolactone or is polycaprolactone.

3. The process according to claim 1 or 2, wherein the powder for additive manufacturing is free or essentially free from any flow aids and calcium phosphates, such as hydroxyapatite.

4. The process according to any one of claims 1 to 3, wherein step c) comprises heating said powder to a temperature between the recrystallization temperature and peak melting temperature of the spherical polyester particles for at least 5 hours and subsequently cooling the powder.

5. The process according to claim 4, wherein heating the powder in step c) comprises heating to a temperature between 5°C above the recrystallization temperature and 1°C below the peak melting temperature of the spherical polyester particles.

6. The process according to any one of claims 4 or 5, wherein the step of subsequently cooling the powder in step c) comprises cooling to a temperature of between 20°C and 25°C at a cooling rate of between 0.1°C / min and 1.0°C / min.

367. The process according to any one of claims 1 to 6, wherein the powder for additive manufacturing comprises spherical polyester particles with a particle size distribution D50 of between 40.0 pm and 100.0 pm.

8. The process according to any one of claims 1 to 7 , wherein thermal spheroidization of the powder in step b) comprises bringing the powder comprising irregular polyester particles into suspension in a carrier gas; and heating said powder by means of radiation generated by a radiation source.

9. The process according to any one of claims 1 to 8, wherein the powder comprising irregular polyester particles is obtained by grinding polyester material, and preferably wherein grinding comprises cryogenic grinding.

10. An additive manufacturing process, the process comprising the steps of i) providing the powder obtained or obtainable by the process according to any one of claims 1 to 9; and, ii) selectively melting or sintering the powder, thereby obtaining a printed article or device.

11. The process according to claim 10, wherein the additive manufacturing comprises powder bed fusion, preferably powder bed fusion techniques comprising sintering.

12. The process according to claim 10 or 11, wherein the device is a medical device, preferably a bioresorbable implant, and more preferably a breast implant, splint, stent, tissueregeneration scaffold, drug-delivery device, or fixation device.

13. A powder for additive manufacturing obtained or obtainable by means of the process according to any one of claims 1 to 9; wherein the powder preferably comprises spherical polyester particles, wherein greater than 50 vol.% of the spherical polyester particles have an average particle size of from at least 10.0 pm to at most 150.0 pm; and a circularity of greater than 0.85.

14. Use of the powder according to claim 13, or obtained or obtainable by the process according to any one of claims 1 to 9, in an additive manufacturing process, preferably an additive manufacturing process comprising powder bed fusion.

15. A device, preferably a medical device, manufactured from the powder according to claim 13; or manufactured by means of the process according to any one of claims 10 to 12.

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