Thermoplastic polymer powder with a wide particle size distribution

Abstract

The present invention relates to a thermoplastic polymer powder comprising particles having a Hausner ratio of 1.30 or less and a particle size distribution characterized by a span of 1.0 or more. The present invention also relates to the use of such powder for the construction of three-dimensional articles, for the coating of surfaces, and for the manufacture of articles by rotational molding. The present invention also relates to a method for preparing the thermoplastic polymer powder and a method for encapsulating thermoplastic polymer particles with at least one additive.

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic polymer powder and its use in a process for building three-dimensional articles for coating or rotational molding, and also to articles manufactured therefrom. The present invention also relates to a method for preparing the thermoplastic polymer powder and to a method for encapsulating thermoplastic polymer particles with at least one additive. [Background technology]

[0002] The construction of three-dimensional (3D) articles can be used, for example, to manufacture prototypes or various parts in the fields of automotive, nautical, aviation, aerospace, medicine (in particular for the production of prosthetics, hearing systems, tissues, etc.), textiles, clothing, fashion, decoration, electronic housings, telephones, home automation, computers, lighting, sports and industrial tools.

[0003] Among the techniques for manufacturing 3D articles, the sintering manufacturing process is particularly advantageous. According to this method, a layer of polymer powder is conventionally selectively irradiated briefly with electromagnetic radiation (e.g., laser beam, infrared, ultraviolet) in a chamber, resulting in the melting of powder particles bombarded by the radiation. The melted particles coalesce and solidify to form a solid mass. This method can produce 3D articles by simply repeatedly irradiating layers of freshly applied powder.

[0004] Polymer powders used in processes for the layer-by-layer fabrication of 3D articles are often produced by milling. This process produces particles with highly variable and angular shapes, typically with a wide particle size distribution. Due to these irregular shapes and the presence of sharp angles and protruding edges within the particles, powders produced by milling have relatively low packing (characterized by a high Hausner ratio), which can hinder their use in processes for the fabrication of 3D articles, particularly by sintering, due to their reduced pourability (or free-flowing properties). Specifically, problems with powder free flow can lead to the risk of voids being introduced when stacking particles to form an object (especially by selective laser sintering or SLS). Furthermore, poor free-flowing powders can lead to surface defects (agglomerates, powder flow lines) in other techniques, such as rotational molding, fluidized-bed dip coating, or electrostatic spraying.

[0005] Furthermore, grinding often generates fibrils or short fibers, which hinder flow and dispersion. In the process for manufacturing 3D objects, these particles, due to their special shape, often cause poor appearance of the resulting parts when located at the edge of the part being built. Furthermore, during powder transfer, these fibers or fibrils tend to bond with each other and form balls, which is the cause of defects in most powder processing processes.

[0006] Finally, milled powders often have a larger developed surface area than powders obtained by dissolution / precipitation, which, when dry mixed, require fewer additives (such as flow regulators) to achieve the same flowability.

[0007] Alternatively, powders may be produced by solution / precipitation processes. However, such processes typically result in powders containing monodisperse particles (i.e., having a narrow particle size distribution), which can lead to poor particle coalescence when the powder is used (e.g., in 3D printing or in surface coating or molding processes). Specifically, unlike monodisperse systems, a wide particle size distribution allows the finest particles of the distribution to fit between the largest particles, minimizing voids between the particles.

[0008] Furthermore, powders with low span (i.e., narrow particle size distribution) often exhibit high flowability (starting from a specific particle size depending on the powder material). This "flowy" nature of the flow can lead to the formation of waves in front of the doctor blade or leveling roller, which can adversely affect the good spreading of the SLS powder layer. In rotational molding, high powder flowability often results in parts with poor thickness control (due to centrifugal separation), primarily in the mold cavity. The use of low-span powders in rotational molding is undesirable because a wide particle size distribution can lead to the gradual buildup of a film lining the mold. Specifically, finer particles reach their softening (or melting) temperature before larger particles, so the coating gradually builds up from the mold wall toward the inner surface of the part, avoiding the formation of voids.

[0009] One example of a powder for 3D printing applications is described in U.S. Patent Publication No. 2021 / 0130608, which relates to a biocompatible polymer powder specifically intended for use in 3D printing of medical devices, and specifically includes a bioceramic as a flow agent.

[0010] Therefore, there is a real need to provide polymer powders that exhibit better pourability and dispersibility, and that allow the production of objects that are less porous, more rigid, and have smoother surfaces, especially when used to build 3D articles. Summary of the Invention

[0011] The present invention relates first to a thermoplastic polymer powder comprising particles having a Hausner ratio of 1.30 or less and a particle size distribution characterized by a span of 1.0 or more.

[0012] In some embodiments, the thermoplastic polymer is a semi-crystalline thermoplastic polymer.

[0013] In some embodiments, the thermoplastic polymer is selected from the group consisting of polyamides, vinylidene fluoride homopolymers and copolymers, copolymers comprising polyamide blocks and polyether blocks, thermoplastic polyurethanes, copolymers comprising polyester blocks and polyether blocks, polycarbonates, polystyrenes, polyaryletherketones, polyolefins, and combinations thereof.

[0014] In some embodiments, the thermoplastic polymer is at least one polyamide, preferably polyamide 11, polyamide 12, and / or polyamide 6, and / or a copolymer comprising polyamide blocks and polyether blocks, where preferably the polyamide blocks are polyamide 6, polyamide 11, polyamide 12, polyamide 6.10, polyamide 10.10, and / or polyamide 10.12 blocks and the polyether blocks are blocks derived from polyethylene glycol, propylene glycol, polytrimethylene glycol, and / or polytetrahydrofuran.

[0015] In some embodiments, the powder has a Hausner ratio of 1.28 or less, preferably 1.20 or less, and more preferably 1.15 or less.

[0016] In some embodiments, the powder comprises particles having a particle size distribution characterized by a span of 1.0 to 2.5, preferably 1.0 to 2.0.

[0017] In some embodiments, the powder preferably comprises at least one additive selected from the group consisting of flow agents, mineral fillers, fibers, polymer powders, dyes, pigments, fire resistant additives, antioxidant stabilizers, light stabilizers, impact modifiers, antistatic agents, flame retardants, and mixtures thereof.

[0018] The invention also relates to the use of such powders for building three-dimensional articles, preferably layer by layer, more preferentially by sintering, even more preferentially by electromagnetic radiation mediated sintering.

[0019] The present invention also relates to the use of a powder as described above for coating a surface, preferably a metal surface.

[0020] The invention also relates to the use of a powder as described above for producing an article by rotational molding.

[0021] The present invention also provides a method for preparing a thermoplastic polymer powder, comprising the steps of: a) providing a thermoplastic polymer powder; b) heating said powder by an energy source having a temperature between 600 and 10,000°C, preferably between 600 and 8,000°C, more preferentially between 1,000 and 3,000°C; c) preferably spraying the powder; d) cooling the powder; e) recovering the powder; The present invention relates to a method, including:

[0022] In some embodiments, the powder prepared is a powder as defined above.

[0023] In some embodiments, the step of providing a thermoplastic polymer powder comprises grinding a thermoplastic polymer or dissolving a thermoplastic polymer in a solvent and precipitating the thermoplastic polymer from the solvent.

[0024] The present invention also provides a method for encapsulating thermoplastic polymer particles with at least one additive, comprising the steps of: a) providing thermoplastic polymer particles; b) mixing the thermoplastic polymer particles with at least one additive, preferably selected from the group consisting of flow agents, mineral fillers, fibers, polymer powders, dyes, pigments, fire resistant additives, antioxidant stabilizers, light stabilizers, impact modifiers, antistatic agents, flame retardants, and mixtures thereof, to form a thermoplastic polymer powder; c) heating said powder by an energy source having a temperature between 600 and 10,000°C, preferably between 600 and 8,000°C, more preferentially between 1,000 and 3,000°C; d) optionally spraying with a powder; e) cooling the powder; f) recovering the powder; The present invention relates to a method, including:

[0025] In some embodiments, the step of providing thermoplastic polymer particles comprises grinding a thermoplastic polymer or dissolving a thermoplastic polymer in a solvent and precipitating the thermoplastic polymer from the solvent.

[0026] In some embodiments, cooling is accomplished by contacting the powder with cold gas, preferably compressed air, or cold water.

[0027] In some embodiments, the powder is collected in a collection tank or cyclone.

[0028] In some embodiments, the method further comprises sieving the recovered powder and / or mixing the recovered, optionally sieved, powder with at least one additive, preferably selected from the group consisting of flow agents, mineral fillers, fibers, polymer powders, dyes, pigments, fire resistant additives, antioxidant stabilizers, light stabilizers, impact modifiers, antistatic agents, flame retardants, and mixtures thereof.

[0029] The invention also relates to a three-dimensional article manufactured from a powder as described above or from a composition as described above, preferably by layer-by-layer printing, more preferentially by sintering.

[0030] The present invention makes it possible to meet the above-mentioned needs. More specifically, it provides a thermoplastic polymer powder that exhibits greater pourability, better dispersibility, and improved coalescence during use. Furthermore, when the powder is used to build three-dimensional objects, such as by a sintering process, it is possible to obtain objects with smoother and more homogeneous surfaces, which in particular makes it easier to further process the surface of the object, and which also allows for a higher density and therefore better mechanical properties, especially high rigidity. The powder according to the invention also allows for good particle layering, which ensures good dimensional stability of successive deposited layers and therefore good retention of the part during construction. Furthermore, the improved thermal stability of the powder according to the invention makes it possible to improve the recyclability of the powder in other construction processes.

[0031] This is achieved by having both a low Hausner ratio for the powder (high untapped density compared to the tapped density of the powder) and at the same time a relatively broad particle size distribution (high span).

[0032] The present invention also provides a method for preparing thermoplastic polymer powders that makes it possible to obtain powders with both a broad particle size distribution (high span) and high flowability (low Hausner ratio). Furthermore, the method according to the invention makes it possible to remove at least a portion of the very fine particles that can cause contamination, especially in 3D printing or rotational molding equipment, when the powder is used and that are difficult to remove by other selection steps such as sieving.

[0033] This is achieved by subjecting the powder to a processing step which involves heating with an energy source having a temperature of 600°C to 10,000°C, followed by cooling.

[0034] The present invention also provides a method for encapsulating thermoplastic polymer particles with at least one additive, which allows for maintaining a homogeneous distribution of the additive in the powder over time and reduces particle coalescence. In certain embodiments where the additive comprises fibers, the method according to the present invention allows for maintaining the random orientation of the fibers over time, thereby maintaining the isotropy of the powder. [Brief explanation of the drawings]

[0035] [Figure 1] 1 shows a micrograph obtained by scanning electron microscopy (SEM, 160x magnification) of Powder 1' described in Example 1 below. [Figure 2] 1 shows a photomicrograph obtained by scanning electron microscopy (160x magnification) of Powder A' described in Example 1 below. [Figure 3] 1 shows a photomicrograph obtained by scanning electron microscopy (160x magnification) of powder 2' described in Example 1 below. [Figure 4] 1 shows a photomicrograph obtained by scanning electron microscopy (160x magnification) of Powder B' described in Example 1 below. [Figure 5] 1 shows a photomicrograph obtained by scanning electron microscopy (160x magnification) of powder C' described in Example 1 below. DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention will now be described in more detail and in a non-limiting manner.

[0037] Unless otherwise indicated, all percentages regarding amounts are by weight.

[0038] As used herein, an amount given for a species is applicable to that species according to all definitions (as set forth herein), including more restrictive definitions.

[0039] powder The present invention relates to a thermoplastic polymer powder. The term "thermoplastic polymer powder" is understood to mean a powder that at least comprises particles containing at least one thermoplastic polymer. For the purposes of the present invention, therefore, a "thermoplastic polymer powder" may also comprise components other than a thermoplastic polymer (in the particles containing a thermoplastic polymer or in the particles not containing a thermoplastic polymer), such as additives.

[0040] The thermoplastic polymer may be semi-crystalline or amorphous, preferably semi-crystalline.

[0041] "Semicrystalline thermoplastic polymer" is understood to mean a thermoplastic polymer having: a) crystallization temperature (Tc) determined in DSC (differential scanning calorimetry) during a cooling process at a rate of 20 K / min in accordance with ISO standard 11357-3:2013; b) melting temperature (Tm) determined in accordance with ISO standard 11357-3:2013 during a heating step at a rate of 20 K / min in a DSC; c) An enthalpy of fusion (ΔHf) of more than 5 J / g, preferably more than 10 J / g, for example more than 20 J / g, and usually less than 200 J / g, preferably less than 150 J / g, for example less than 100 J / g, or less than 50 J / g, determined in a DSC during a heating step at a rate of 20 K / min according to ISO standard 11357-3:2013.

[0042] Advantageously, the semi-crystalline thermoplastic polymer has a melting temperature Tm of between 100 and 300° C., preferably between 120 and 200° C. The Tm is measured as described above and corresponds to the Tm measured during the first heating.

[0043] The semi-crystalline thermoplastic polymer may have a crystallization temperature Tc of 40 to 250° C., preferably 45 to 200° C., for example 45 to 150° C. Tc is measured as described above.

[0044] Typically, Tm and Tc are determined directly from the semi-crystalline thermoplastic polymer powder. When the powder is a mixture of polymers, Tm is understood to mean the lowest melting temperature of the mixture of polymers, and Tc is understood to mean the highest melting temperature of the mixture of polymers.

[0045] Preferably, the thermoplastic polymer is selected from the group consisting of polyamide (PA), vinylidene fluoride homopolymers and copolymers (PVDF), copolymers comprising polyamide blocks and polyether blocks (PEBA), thermoplastic polyurethanes (TPU), copolymers comprising polyester blocks and polyether blocks (COPE), polycarbonate (PC), polystyrene (PS), polyaryletherketones such as polyetheretherketone (PEEK), polyolefins such as polyethylene and polypropylene, and combinations thereof.

[0046] Thus, the thermoplastic polymer according to the invention may comprise or be at least one polyamide, whether it be a homopolyamide or a copolyamide, or a mixture thereof.

[0047] In some embodiments, the thermoplastic polymer may be, in particular, an elastomeric thermoplastic polymer, more particularly selected from PEBA copolymers, TPU and / or COPE copolymers.

[0048] Of course, the designation PEBA in this specification of the present invention relates in particular to Pebax® products sold by Arkema, to Vestamid® products sold by Evonik, to Grilamid® products sold by EMS, to PEBA products of the Pelestat® type sold by Sanyo or equally to any other PEBA product from another supplier.

[0049] In some embodiments, the elastomeric thermoplastic polymer may also be selected from styrene block copolymers (TPS), thermoplastic polyolefin elastomers (TPO), and / or thermoplastic vulcanizates (TPV). Examples of commercially available elastomeric thermoplastic polymers include, for example, Cawiton®, Thermolast K®, Thermolast M®, Sofprene®, Dryflex®, and Laprene® (TPS), Desmopan® or Elastollan® (TPU), Santoprene®, Termoton®, Solprene®, Thermolast V®, Vegaprene®, or Forprene® (TPV), and For-TecE® or Engage, Ninjaflex® (TPO) products.

[0050] In some embodiments, the thermoplastic polymer comprises or is a polymer selected from polyoxymethylene (POM) homopolymers and copolymers, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphthalamide (PPA), and poly(p-phenylene terephthalamide), and mixtures thereof.

[0051] In some embodiments, the thermoplastic polymer includes or is polycarbonate (PC).

[0052] In some embodiments, the thermoplastic polymer includes or is polystyrene (PS).

[0053] In some embodiments, the thermoplastic polymer includes or is polyetheretherketone (PEEK).

[0054] The thermoplastic polymer may consist of a single polymer, in particular as described above, or may comprise or consist of a mixture of (preferably semi-crystalline) thermoplastic polymers, in particular a mixture of any of the (preferably semi-crystalline) thermoplastic polymers as described above.

[0055] The thermoplastic polymer powder according to the present invention has a Hausner ratio of 1.30 or less. As is known, the Hausner ratio of a powder is defined as the ratio of the tapped density to the untapped density (also called vented density or apparent density) of the powder. The tapped density and vented density can be measured, for example, using a STAVII tamping volumeter in accordance with ISO standard 3953:2011. Advantageously, the thermoplastic polymer powder has a Hausner ratio of 1.28 or less, preferably 1.25 or less, more preferably 1.20 or less, more preferably 1.15 or less, more preferably 1.12 or less, and more preferably 1.10 or less. In some embodiments, the powder has a Hausner ratio of 1.07 or less, or 1.05 or less, or 1.02 or less, or from 1.0 to 1.05, or from 1.05 to 1.10, or from 1.10 to 1.15, or from 1.15 to 1.20, or from 1.20 to 1.22, or from 1.22 to 1.25, or from 1.25 to 1.28, or from 1.28 to 1.30. The lower the Hausner ratio of a powder, the better the permeability (free flowability) of the powder.

[0056] The thermoplastic polymer powder according to the invention is characterized by one or more spans. The span parameter defines the particle size distribution of the particles of the powder and is calculated in a known manner by the following formula: span = (Dv90 - Dv10) / Dv50, where: - Dv90 represents the 90th percentile particle size on a volume basis of the cumulative particle size distribution (in other words, the diameter corresponding to which the cumulative function of the volume-weighted particle diameters is equal to 90%), - Dv10 represents the 10th percentile particle size on a volume basis of the cumulative particle size distribution (in other words, the diameter corresponding to which the cumulative function of particle diameters weighted by volume is equal to 10%), - Dv50 is the volume median diameter of the particle, which corresponds to the 50th percentile particle size by volume of the cumulative particle size distribution.

[0057] Dv50, Dv90 and Dv10 may be measured by laser diffraction particle size analysis according to ISO standard 13320:2009, for example on a Malvern Insitec® diffractometer.

[0058] Preferably, the particles of the powder have a span of 1.0 to 2.5, more preferentially 1.0 to 2.0, even more preferentially 1.2 to 2.0. In particular, the particles of the powder may have a span of 1.0 to 1.2, or 1.2 to 1.5, or 1.5 to 1.7, or 1.7 to 2.0, or 2.0 to 2.2, or 2.2 to 2.5.

[0059] Preferably, the particles of the powder have a Dv50 of 20 to 500 μm, more preferentially 30 to 250 μm, more preferentially 40 to 120 μm.

[0060] Preferably, the particles of the powder have a Dv90 of 50 to 800 μm, more preferentially 60 to 500 μm, more preferentially 70 to 130 μm.

[0061] Preferably, the particles of the powder have a Dv10 of 5 to 100 μm, more preferentially 10 to 80 μm, more preferentially 15 to 60 μm.

[0062] In some embodiments, the powder comprises a cumulative fraction of particles sized 10 μm or less of 1 wt. % or less, preferably 0.8 wt. % or less, based on the total weight of the powder.

[0063] In some embodiments, the powder comprises a cumulative fraction of particles with a size of 30 μm or less of 10% by weight or less, preferably 5% by weight or less, more preferentially even 2% by weight or less, or 1% by weight or less, relative to the total weight of the powder.

[0064] The cumulative fraction of particles is measured according to ISO standard 13320:2009.

[0065] For the purposes of the present invention, particle size means the average volume-equivalent diameter of said particles.

[0066] Powders with a low cumulative fraction of fine particles as defined above (particularly particles with a size of 30 μm or less, preferably 10 μm or less) have certain advantages in 3D printing or rotational molding processes, since these fine particles are particularly likely to cause contamination of the 3D printing or rotational molding equipment when the powder is used and are difficult to remove by other selection steps such as sieving.

[0067] In some embodiments, powders according to the present invention consist of or consist essentially of at least one thermoplastic polymer.

[0068] The powder may further comprise one or more additives, preferably at least one additive selected from the group consisting of flow agents, mineral fillers, fibers, polymer powders, dyes, pigments, fire-resistant additives, antioxidant stabilizers, light stabilizers, impact modifiers, antistatic agents, flame retardants, and mixtures thereof.

[0069] The powder may comprise at least one flow agent, the term "flow agent" being understood to mean an agent that makes it possible to improve the pourability and further homogeneity of the powder, in particular during the sintering process.

[0070] The flow agent may be selected, for example, from silica, especially precipitated silica, hydrated silica, vitreous silica, fumed silica and pyrogenic silica, glassy oxides, especially glassy phosphates and glassy borates, alumina, for example amorphous alumina, TiO2, calcium silicates, magnesium silicates, for example talc, mica, kaolin, attapulgite, waxes, and mixtures thereof.

[0071] The flow agent may be present in the composition in an amount of up to 5%, preferably up to 3%, relative to the total weight of the composition, more particularly from 0.1% to 2.5%, preferably from 0.1% to 2%, more preferably from 0.5% to 2%, for example from 0.5% to 1.5%, relative to the total weight of the composition.

[0072] The flow agent is generally in the form of a powder, preferably substantially spherical particles. The flow agent in the composition may have particles with a volume median diameter (Dv50) of 20 μm or less, preferably 15 μm or less, more preferentially 10 μm or less, and more preferentially 1 μm or less. For example, the median diameter Dv50 of the flow agent particles may be 10 nm to 100 nm, 100 nm to 1 μm, or 1 μm to 20 μm.

[0073] Alternatively, the powder may be free of flow agents, especially those mentioned above.

[0074] The powder may comprise one or more mineral fillers selected from, for example, carbonate mineral fillers, in particular calcium carbonate, magnesium carbonate, dolomite and / or calcite, barium sulfate, calcium sulfate, dolomite, alumina hydrate, wollastonite, montmorillonite, zeolites, perlite, nanofillers (fillers on the order of nanometers), such as nanoclays and / or carbon nanotubes, carbon black, glass fibers, carbon fibers, and combinations thereof.

[0075] The powders according to the invention may more particularly comprise organic additives, such as powders of polymers (other than thermoplastic polymers), in particular those having a melting temperature higher than the maximum temperature experienced by the powder during its use (for example during the process of building a 3D article layer by layer), in particular those having a Young's modulus of 1000 MPa or more.

[0076] In some embodiments, the powder is free of mineral fillers and / or (preferably and) organic additives, and in particular free of polymer powders other than thermoplastic polymers.

[0077] The powder may contain mineral fillers and organic additives in an amount of 60% by weight or less, preferably 30% by weight or less, more preferably 1% by weight or less, relative to the total weight of the composition, for example 0.05% by weight to 60% by weight, preferably 1% by weight to 30% by weight, preferably 1% by weight to 20% by weight, more preferably 1% by weight to 10% by weight.

[0078] The powder of the present invention may contain one or more additives selected from dyes, pigments, particularly coloring pigments and infrared-absorbing pigments, fire-resistant additives, antioxidant stabilizers, light stabilizers, impact modifiers, antistatic agents, flame retardants, and mixtures thereof. These additives are preferably in the form of powders having a Dv50 of less than 20 μm. These additives may be present in the composition in an amount of 0.05% to 5% by weight, based on the total weight of the composition.

[0079] In some embodiments, the powder consists essentially of or consists of particles comprised of a thermoplastic polymer and one or more additives selected from flow agents, mineral fillers, polymer powders, dyes, pigments, fire resistant additives, antioxidant stabilizers, light stabilizers, impact modifiers, antistatic agents, flame retardants, and mixtures thereof.

[0080] Manufacturing method The present invention also relates to a method for preparing a thermoplastic polymer powder, in particular the above-mentioned thermoplastic polymer powder.

[0081] The preparation process involves providing a powder of a thermoplastic polymer and heating it with an energy source, preferably a flame, at a temperature of 600 to 10,000°C. For purposes of the present invention, it should be understood that the temperature ranges given for the energy source characterize the temperature of the energy source itself (its core), and not the temperature of the heated powder particles. The use of such an energy source allows for rapid heating of the particles by increasing heat transfer.

[0082] The step of providing a powder may include the manufacture of such a powder. The provided thermoplastic polymer powder can be obtained by any suitable means. Advantageously, the powder is obtained by grinding a thermoplastic polymer (e.g., in the form of pellets). In these embodiments, the thermoplastic polymer (or a mixture of thermoplastic polymers) is preferably pre-melted (e.g., at a temperature between 150°C and 300°C) and then solidified and ground. Grinding can be carried out using a suitable grinding device, such as a pin mill, a hammer mill, a classifier mill, or a fluidized bed air jet mill. Advantageously, grinding is cryogenic grinding. In this case, the thermoplastic polymer is cooled in a first step to a temperature below its glass transition temperature, for example, 10 to 50°C below the glass transition temperature of the thermoplastic polymer. Thus, the thermoplastic polymer can be cooled to a temperature below -10°C, preferably below -50°C, and more preferably below -80°C. Cooling the thermoplastic polymer before grinding can be carried out, for example, using liquid nitrogen, liquid carbon dioxide, dry ice, or liquid helium.

[0083] Alternatively, the provided powder can be obtained by a dissolution / precipitation process (especially when the thermoplastic polymer is polyamide and / or PEBA). In these embodiments, the method includes dissolving the thermoplastic polymer in a solvent and precipitating the thermoplastic polymer from the solvent. More specifically, the method can include contacting the thermoplastic polymer (e.g., in the form of pellets) with the solvent to obtain a mixture, heating the mixture to dissolve the copolymer in the solvent, and cooling the mixture to obtain the precipitated polymer in powder form. The solvent for dissolving the thermoplastic polymer can be selected from ethanol, propanol, butanol, isopropanol, heptanol, formic acid, acetic acid, N-methylpyrrolidone, N-butylpyrrolidone, butyrolactam, and / or caprolactam. The thermoplastic polymer has a mass fraction in the solvent of 0.05 to 0.5, preferably 0.1 to 0.3. Heating of the thermoplastic polymer / solvent mixture may be carried out at (or to) a temperature of, in particular, 100 to 160°C, preferably 120 to 150°C, and / or may have a duration of 1 to 6 hours, preferably 1 to 3 hours. The mixture is then cooled to crystallize and precipitate the copolymer in powder form. This cooling may be carried out to a temperature of 50°C or higher, for example in the range of 50 to 90°C, at a rate of 10 to 100°C per hour, preferably 10 to 60°C per hour. The dissolution / precipitation step may include, after cooling the mixture, drying the thermoplastic polymer powder, for example in an oven. Drying may be carried out at a temperature of 10 to 150°C, preferably 25 to 85°C, and may be carried out under vacuum (in particular at a pressure of more than 10 mbar, preferably more than 50 mbar) or at atmospheric pressure.

[0084] Preferably, the powder provided is a powder obtained by milling, which results in a powder with a higher span.

[0085] In any manufacturing process, the powder may be subjected to a selection step, in particular a selection step carried out by sieving or a dynamic selector.

[0086] The thermoplastic polymer powder is then subjected to a heating step. Preferably, the powder is heated by a torch or by any other means capable of generating a flow of hot gas, more preferentially by a torch. Advantageously, the torch is an oxyfuel torch (i.e., using dioxygen O2 as oxidizer), more preferentially an oxypropane torch (i.e., using dioxygen and propane as oxidizers), an oxybutane torch (i.e., using dioxygen and butane as oxidizers) or an oxyacetylene torch (i.e., using dioxygen and acetylene as oxidizers), even more preferentially an oxypropane torch.

[0087] Highly preferably, the method includes the step of atomizing the powder. Preferably, the steps of heating the powder and atomizing the powder are partially simultaneous. In particular, they may be performed using the same apparatus.

[0088] Preferably, a flame spray device is used as the torch. Such a device allows the powder, advantageously carried by a carrier gas, especially air, to be sprayed through the flame. For example, the IBEDA MiniSprayJet F311FX model device can be used. This self-contained device operates simply by connecting it to an energy source.

[0089] Advantageously, the method according to the invention allows, by suitable adjustment of the energy source (preferably a flame), to improve the particle size of the powder by burning off at least a portion of the very fine particles (in particular particles of a size of 30 μm or less, preferably 10 μm or less), the significant presence of which can in certain methods cause contamination of the equipment used, in particular SLS 3D printing and rotational molding equipment.

[0090] Preferably, the energy source (preferably a flame) has a temperature of 600 to 8000°C, more preferably 600 to 4000°C, preferably 1000 to 3000°C. The energy source may in particular have a temperature of 600 to 800°C, or 800 to 1000°C, or 1000 to 1200°C, or 1200 to 1500°C, or 1500 to 1700°C, or 1700 to 2000°C, or 2000 to 2200°C, or 2200 to 2500°C, or 2500 to 2700°C, or 2700 to 3000°C, or 3000 to 3500°C, or 3500 to 4000°C, or 4000 to 6000°C, or 6000 to 8000°C, or 8000 to 10000°C.

[0091] The contact time of the powder with the energy source (preferably the flame) is advantageously between 0.01 and 1 second, preferably between 0.02 and 0.1 seconds, in particular the contact time of the powder with the flame is 0.01 to 0.02 seconds, or 0.02 to 0.04 seconds, or 0.04 to 0.06 seconds, or 0.06 to 0.08 seconds, or 0.08 to 0.1 seconds, or 0.1 to 0.25 seconds, or 0.25 to 0.5 seconds, or 0.5 to 0.75 seconds, or 0.75 to 1 second.

[0092] Heating of thermoplastic polymer powders by the energy source defined above makes it possible to induce partial melting at the surface of the powder particles, leading to rounding or spheroidization (i.e., complete roundness) of the powder particles, which reduces the Hausner ratio of the powder and makes it easier to pour.

[0093] Generally, during the production of a powder, the Hausner ratio of the powder can be reduced by increasing the energy of the heat treatment of the powder (allowing melting at the particle surface). For example, this means: - By increasing the flow rate of the powder being sprayed; - By increasing the flow rate of the carrier air (or gas); - By increasing the flow rate of the oxidizer; - By increasing the fuel flow rate; - By increasing the pressure of the cooling air (or gas); - By increasing the distance between the energy source (e.g., atomizer) and the collection device, thereby extending the heating time of the particles. This can be done.

[0094] Furthermore, the method according to the invention has the advantage that it reduces the span of the starting powder very little or not at all, making it possible to obtain powders with a span of 1.00 or greater.

[0095] The flow rate of the carrier gas may be 0 to 0.08 MPa, particularly 0 to 0.05 MPa.

[0096] The flow rate of the oxidant may be between 15 and 70 l / min, in particular between 20 and 60 l / min.

[0097] The fuel flow rate may be between 10 and 40 l / min, in particular between 15 and 25 l / min.

[0098] The pressure of the cooling gas may be 0.15 to 0.8 MPa, particularly 0.2 to 0.6 MPa.

[0099] Very preferably, the powder is then cooled. Preferably, the powder can be cooled by contacting it with a fluid, in particular a cold gas and / or a cold liquid. The term "cold gas" is understood for the purposes of the present invention to mean a gas having a temperature of at most 30°C, and the term "cold liquid" is understood for the purposes of the present invention to mean a liquid having a temperature of at most 20°C. The cold gas is more preferentially air, more particularly compressed air. The cold liquid is advantageously water.

[0100] The preparation method preferably includes a step of recovering the powder. Advantageously, the recovery of the powder is carried out at least partially simultaneously with the cooling. The recovery of the powder very preferably includes contacting the powder with a fluid (gas and / or liquid), in particular with a fluid used to cool the powder. The fluid, in particular a gas, can be in motion, e.g., a rotational motion, so as to entrain the powder particles. Contacting the powder with a fluid (in particular in motion) makes it possible to reduce agglomeration of the powder particles that may occur before cooling is complete.

[0101] The powder can be collected in a suitable collection device, such as a collection tank, or preferably in a suitable cyclone. The use of a cyclone is particularly advantageous because it allows the powder particles to be separated from the carrier gas (the particles are collected at one end of the device, and the powder carrier gas is discharged at the other end of the device). Compared to a collection tank, the use of a cyclone can reduce product loss and therefore increase powder yield.

[0102] The recovery device may in particular contain and / or be surrounded by a fluid that is used to cool the powder.

[0103] Preferably, the distance between the energy source, preferably the flame (its base) (eg the tip of the gun in the case of a spray device) and the collection device is 1 to 2.5 m, preferably 1.3 to 2.2 m, for example 1.5 m or 2 m.

[0104] The method may include a step of selecting the particles of the recovered powder according to a desired particle size, in particular by sieving.

[0105] The method may optionally include mixing the particles of thermoplastic polymer with other optional ingredients of the powder, in particular the additives mentioned above.

[0106] Advantageously, this mixture is a dry mixture of powdered components and is in powder form. When the powder comprises two or more components, the mixing can be carried out in one stage (all components are added to the mixture at the same time) or in several stages (some components are premixed first, then the others are added), and the components can be mixed in any order. The mixing can be carried out in any device suitable for mixing powders.

[0107] Alternatively, all or a portion of the additives may be mixed with the thermoplastic polymer during the step of providing the thermoplastic polymer powder before preparing the thermoplastic polymer powder according to the present invention. Thus, when preparing the powder by milling, the additives may be mixed before melting the thermoplastic polymer or with the milled thermoplastic polymer powder. When preparing the powder by solution / precipitation, the additives may be mixed with the thermoplastic polymer before dissolving it in a solvent, after dissolving it in a solvent and before precipitating, or with the precipitated thermoplastic polymer powder. When only a portion of the additives are mixed with the thermoplastic polymer before preparing the powder according to the present invention by heating with an energy source having a temperature of 600 to 10,000°C (e.g., a flame), the remainder of the additives are mixed with the powder by dry blending.

[0108] In some embodiments, at least one additive is added to the thermoplastic polymer powder before the heating step, and the method includes a step of atomizing the powder. In these embodiments, the heating and atomizing steps allow at least a portion of the powder particles to be encapsulated with at least a portion of the additive. Encapsulating the powder particles with the additive can integrally bond the thermoplastic polymer and the additive, advantageously reducing fractionation of the additive powder and maintaining uniform distribution of the additive in the powder. Encapsulation can also reduce particle coalescence. Furthermore, when the additive is a fiber, encapsulation can maintain the fibers in a random orientation, imparting isotropy to the powder.

[0109] Method for removing fines The present invention also relates to a method for removing fines from a powder, the term "removing fines" being understood to mean reducing the amount of particles in the powder that are 30 μm or less in size, preferably 10 μm or less. The amount of particles in a powder that are less than a given size can be determined by laser diffraction particle size distribution measurement, for example using a Malvern Insitec® diffractometer, in accordance with ISO standard 13320:2009.

[0110] This method according to the invention comprises: a) providing a thermoplastic polymer powder; b) heating said powder by an energy source having a temperature between 600 and 10,000°C, preferably between 600 and 8,000°C, more preferentially between 1,000 and 3,000°C; c) preferably spraying the powder; d) cooling the powder; e) recovering the powder; Includes.

[0111] What was described in the previous section regarding the method for preparing thermoplastic polymer powders is equally applicable to this method.

[0112] Generally, the higher the temperature of the energy source, the greater the reduction in the amount of particles below 10 μm.

[0113] Advantageously, the method of removing fines allows for a reduction in the amount of particles below 20 μm in size and / or a reduction in the amount of particles below 30 μm in size in the powder.

[0114] Advantageously, the recovered powder contains a cumulative fraction of particles with a size less than or equal to 10 μm less than or equal to 1% by weight, preferably less than or equal to 0.8% by weight, relative to the total weight of the powder.

[0115] Advantageously, the powder comprises a cumulative fraction of particles with a size of less than or equal to 30 μm of less than or equal to 10% by weight, preferably less than or equal to 5% by weight, more preferentially even less than or equal to 2% by weight, or less than or equal to 1% by weight, relative to the total weight of the powder.

[0116] Advantageously, the recovered powder (i.e. the powder from which fines have been removed) is as described above in the "Powder" section, and in particular comprises particles having a Hausner ratio of 1.30 or less and a particle size distribution characterized by a span of 1.0 or more.

[0117] Encapsulation Process The present invention also relates to a method for encapsulating thermoplastic polymer particles with at least one additive.

[0118] This method according to the invention comprises: a) providing thermoplastic polymer particles; b) mixing the thermoplastic polymer particles with at least one additive to form a thermoplastic polymer powder; c) heating said powder by an energy source having a temperature between 600 and 10,000°C, preferably between 600 and 8,000°C, more preferentially between 1,000 and 3,000°C; d) optionally spraying with a powder; e) cooling the powder; f) recovering the powder; Includes.

[0119] The at least one additive is advantageously in powder form and is preferably chosen from the additives mentioned above in the previous section.

[0120] The thermoplastic polymer particles are mixed with the at least one additive, preferably by dry blending.

[0121] Preferably, the heating and spraying steps are at least partially simultaneous.

[0122] What was described in the previous section regarding the method for preparing a thermoplastic polymer powder can be applied to this method as well. The step of providing thermoplastic polymer particles can be as described in the step of providing a thermoplastic polymer powder in the "Method of Production" section above.

[0123] Advantageously, the recovered powder (i.e., the encapsulated powder) is as described above in the "Powder" section, and in particular comprises particles having a Hausner ratio of 1.30 or less and a particle size distribution characterized by a span of 1.0 or more.

[0124] Purpose The powders or compositions as described above may be used in a method for building 3D articles, preferably layer by layer (also known as 3D printing method), more preferentially by sintering, even more preferentially by electromagnetic radiation mediated sintering, for example using infrared, ultraviolet or preferably laser.

[0125] Preferably, the composition of the present invention is used in a selective laser sintering (SLS) process. The composition can also be used in MJF (multi-jet fusion) and HSS (high speed sintering) type sintering processes.

[0126] The present invention also provides a method for constructing a three-dimensional article, comprising the steps of: a) depositing the above-mentioned powder or the above-mentioned composition in powder form, preferably in the form of a layer; b) sintering the powder, preferably by means of a beam of electromagnetic radiation; The present invention relates to a method, including:

[0127] Preferably, steps a) and b) are repeated to form the three-dimensional article.

[0128] As mentioned above, the powder can be recycled and reused for multiple successive production runs. For example, the powder can be used as is or as a mixture with other recycled or non-recycled powders. Advantageously, after step b) of the method, and preferably after each step b), the non-agglomerated powder can be recycled into the same building process to carry out a subsequent deposition step a) or can be reused in another building process.

[0129] What has been said above in relation to the use of the powder or composition for the construction of three-dimensional articles applies equally to the method for constructing three-dimensional articles.

[0130] The present invention also provides an article made from a powder or composition as described above, preferably by a method as described above.

[0131] In another embodiment, the powder or composition according to the invention can be used to coat a surface. The surface can be completely or partially coated. Advantageously, the coating is a film obtained by melting the above-mentioned thermoplastic polymer powder or the above-mentioned composition in powder form (in particular a film with a thickness of 100 to 550 μm, more preferentially 200 to 500 μm).

[0132] The surface may be of any type, in particular a metal surface, for example the surface of a part selected from the group consisting of ordinary steel or galvanized steel parts, aluminium parts or aluminium alloy parts.

[0133] The present invention also provides a method for coating a surface, comprising the steps of: - contacting a surface with the above-mentioned powder or the above-mentioned composition in powder form; - melting the powder; The present invention relates to a method, including:

[0134] Prior to contacting the surface with the powder, the coating process may include applying a mask to the surface, particularly if the object to be coated needs to be only partially covered by the coating. Applying the mask allows for selective coating of only certain portions of the part to be coated. The powder is then contacted with the unmasked portions of the surface to be coated.

[0135] The powder may be applied to or contacted with the surface by a number of coating techniques well known to those skilled in the art. Preferably, the coating is done via a method selected from the group consisting of fluidized bed dip coating, electrostatic spraying, and thermal powder coating.

[0136] Thus, the coating may be carried out by electrostatic spraying. The step of contacting the surface with the powder or the composition in powder form then comprises: - electrically charging the powder; - spraying an electrically charged powder onto a surface; - heating the powder-coated surface to a temperature above the melting temperature of the thermoplastic polymer; may include:

[0137] Coating by electrostatic spraying consists of depositing electrically charged powder particles on a surface, particularly at ambient temperature. The powder can become charged while passing through the nozzle of the spraying device. The thus charged powder can then be sprayed onto an object containing the surface to be coated, which is connected to zero potential. The coated object can then be placed in an oven at a temperature that allows the powder to melt.

[0138] The powder spraying device can be of any type. Preferably, the nozzle is charged to a high potential of between about 10 kV and about 100 kV, either negative or positive. Preferentially, the powder spraying device is an electrostatic gun, which charges the powder by the corona effect and / or triboelectric charging. Preferably, the powder flow rate in the spraying device is between 10 and 200 g / min, more preferably between 50 and 120 g / min. The electrostatic application temperature of the powder is preferably between 15 and 25°C. The surface's residence time in the oven is preferably between 3 and 15 minutes. Advantageously, the heating temperature of the surface can be between 180 and 300°C, preferably between 200 and 250°C. The heating temperature of the powder-covered surface can preferably be at least 30°C higher than the melting temperature of the thermoplastic polymer, more preferably between 30 and 60°C higher than the melting temperature of the thermoplastic polymer. The surface is then cooled, for example to ambient temperature. If a mask was used, it can be removed.

[0139] Alternatively, the coating can be carried out by fluidized bed dip coating. Thus, the step of contacting the surface with the powder comprises: - heating the surface to a temperature above the melting temperature of the thermoplastic polymer; - immersing the surface in a fluidized bed containing the powder; may include:

[0140] The surface to be coated is preheated to a temperature that allows the powder according to the present invention to melt. The surface is then immersed in a fluidized bed containing the powder. The powder melts on contact with the surface and forms a coating. The coated surface is then preferably cooled. If present, the mask may be removed. Preferably, the fluidizing air used to fluidize the powder is cold, clean, and oil-free. Preferably, the surface is heated to a temperature between 180 and 450°C, preferably between 250 and 350°C. More preferably, the surface is heated to a temperature at least 30°C higher than the melting temperature of the thermoplastic polymer, more preferentially between 30 and 120°C higher than the melting temperature of the thermoplastic polymer. Preferably, the duration of immersion of the surface in the fluidized bed is between 1 and 10 seconds, more preferentially between 3 and 7 seconds. The surface may be immersed in the fluidized bed once or multiple times (each immersion lasting between 1 and 10 seconds, more preferentially between 3 and 7 seconds).

[0141] In another embodiment, the coating is applied by thermal powder coating. The step of contacting the surface with the powder comprises: - heating the surface to a temperature above the melting temperature of the thermoplastic polymer; - spraying a powder onto a surface; Includes.

[0142] The surface heating temperature may be as described above for coating by fluidized bed dip coating. The surface heating temperature is particularly preferably at least 30°C higher than the melting temperature of the thermoplastic polymer, more preferably 30 to 120°C higher than the melting temperature of the thermoplastic polymer. The surface is then cooled, for example to ambient temperature. If a mask was used, it may be removed. The sprayed powder may or may not be electrostatically charged.

[0143] The features described above in relation to the use of powders to coat surfaces (particularly with regard to the description of the surface and the thickness of the coating film) may be applied to the coating process as well.

[0144] The present invention also relates to an object having a surface at least partially covered with a coating obtained (or obtainable) by melting a powder or composition as described above, preferably an object obtained (or obtainable) by a method as described above.

[0145] Another subject of the invention relates to the use of a powder as defined above or a composition as defined above in powder form, for the manufacture of articles by rotational molding (also called rotomolding).

[0146] The present invention also provides a method for manufacturing an article, comprising the steps of: - providing the above-mentioned powder or the above-mentioned composition in powder form; - rotationally molding said powder; The present invention relates to a method, including:

[0147] Rotational molding is a molding process in which powder is introduced into a mold, which can vary in size, shape, thickness, and material. The mold is then rotated and heated, and the powder is heated to its melting point by conduction while in contact with the mold walls. Rotation of the mold (advantageously at a speed of 2 to 40 rpm), preferably along one or two axes (which are preferably perpendicular), allows the molten material to cover the entire inner surface of the mold. The mold is then advantageously cooled, preferably with air or water sprays, preferably while rotating. After the polymer material has solidified, the article can be removed from the mold.

[0148] Advantageously, the step of heating the mold comprises introducing the mold into an oven, the mold being preferably heated to a temperature between 20°C and 60°C above the melting point of the polymer, more preferably between 20°C and 40°C above the melting point.

[0149] The rotational molding process using polymer powders is well known to those skilled in the art.

[0150] The present invention also provides an article obtained (or obtainable) by a rotational molding process as described above. [Example]

[0151] The following examples illustrate the invention without limiting it.

[0152] Example 1 The following powders were prepared or used: Powder 1: Pebax® 3533 commercial powder (Arkema). Powder 2: Pebax® 40R53 commercial powder (Arkema). Powder 3: Pebax® 4533 commercial powder (Arkema). Powder 4: Rilsan® Fine Powders TBLUE 7443 commercial powder (Arkema). Powder 5: Rilsan® Fine Powders TNat BHV commercial powder (Arkema). Powder 6: Orgasol® InventSMOOTH commercial powder (Arkema). - Powder 7: PA2200 commercial powder (EOS). Powder 8: Rilsan® Invent Natural commercial powder (Arkema).

[0153] Portions of Powders 1, 2, 3, 4, 5, and 6 were subjected to the following treatment: the powders were air-pumped from a tank maintained under vibration and then transferred to an IBEDA MiniSprayJet F311FX oxypropane flame atomizer (flame temperature 2000-2600°C). The powders were then atomized using the flame atomizer. The atomized powders were collected in a cyclone recuperator and cooled by circulating compressed air around the cyclone.

[0154] The processing parameters shown in the table below were used to obtain the following powders: [Table 1] TIFF2025542400000002.tif41170

[0155] For all powder treatments, the inlet dry air pressure was 0.6 MPa, the propane pressure was 0.14 MPa, the dioxygen pressure was 0.25 MPa, the inner diameter (mm) / length (mm) ratio of the powder transport pipe to the atomizer was 11 / 2000, and the carrier air pressure was 0 MPa (except for the treatment of powder 1, which was 0.04 MPa).

[0156] Powders 1, A, 2, B, C, 3, and D were then dry mixed with one or more flow agents in a Henschel IAM6L mixer at ambient temperature for 100 seconds while stirring at 9000 rpm. The flow agents and their amounts (by weight) are listed in the table below. The added powders are hereafter referred to as Powders 1', A', 2', B', C', 3', and D', respectively. [Table 2] TIFF2025542400000003.tif41170

[0157] Powders A', B', C', D', E and F are powders according to the invention, and powders 1', 2', 3', 4, 5, 6, 7 and 8 are comparative powders.

[0158] The Hausner ratio and span of the powder were then determined according to the methods described above.

[0159] The results are shown in the table below. [Table 3] TIFF2025542400000004.tif81170

[0160] It was found that powders were obtained that had both a low Hausner ratio (i.e., high free flowing) and a high span. In contrast, commercial powders 6 and 7 have a span of less than 1, and commercial powder 8 has a Hausner ratio of greater than 1.30.

[0161] Micrographs of the particles of powders 1', A', 2', B' and C' are shown in Figures 1, 2, 3, 4 and 5, respectively. It has been observed that the atomizer treatment of the powders makes it possible to round and even spheroidize (in the case of powder C') the particles of the milled powders.

[0162] Example 2 Powders 3' and D' described in Example 1 above were used to produce 1BAXY (in the build plane) specimens in accordance with ISO standard 527 by 3D printing with sintering, more specifically by SLS, in a Sharebot SnowWhite machine under the temperature conditions (powder and chamber) shown in Table 4 below. The laser parameters used were the same for all printing runs and for each of the two powders tested, and were as follows: Each layer of powder to be sintered was scanned at a speed of 40,000 points / second by a 6.3 W power laser applied to the layer at 0.06 mm intervals.

[0163] During the build, the temperature of the powder at the surface of the build tank was set and measured at the surface by an infrared thermal sensor. The air temperature in the chamber was measured by a temperature probe placed inside the machine, less than 10 cm from the build tank.

[0164] The following properties of the test specimens thus constructed were then measured: - Density: measured by the Archimedes buoyancy method described in ISO standard 1183-1:2019; the average density of five specimens was calculated. - Tensile modulus: measured according to ISO standard 527-2 with an Instron 5966 machine; the average value of the tensile modulus of five specimens was calculated.

[0165] High density is evidence that the powder particles are well sintered and the powder is successfully transformed into a part.

[0166] The results are shown in Table 4 below. [Table 4] TIFF2025542400000005.tif22170

[0167] Powder D' according to the invention (low Hausner ratio) allows the construction of parts with better density and better mechanical properties.

[0168] The thermal stability of powders 3' and D' was also evaluated. For this purpose, the powders were aged as follows: for each powder, 100 successive layers were deposited at a temperature of 125 °C using an EOS Formiga P100 machine without the use of a laser. The tapped and untapped densities of each powder were measured before and after aging. The delta density, which corresponds to the difference between the density of the powder after aging and the density of the powder during aging, was calculated.

[0169] The results are shown in the table below. [Table 5] TIFF2025542400000006.tif31170

[0170] The comparative powders are observed to lose density after passing through the press (untapped and tapped), a phenomenon that can be explained by powder agglomeration and / or a decrease in the efficiency of the flow agent due to it being partially fixed to the powder particles.

[0171] In contrast, the powder according to the invention not only does not lose density after passing through the printing press, but may even have higher untapped and tapped densities, and can be easily recycled in new printing processes.

[0172] Example 3 Powder G was prepared by subjecting powder 8 described in Example 1 to the treatment described in Example 1 (process according to the invention), but using the following operating parameters: - Powder pumping air pressure: 0.32MPa; - Cooling air pressure: 0.35MPa; - Propane flow rate: 17.5 l / min; - Dioxygen flow rate: 24.5l / min; - Distance between spray gun and recuperator: 2m; - Carrier air pressure: MPa.

[0173] Particle size analysis of Powders 1', A', 3', D', 4, E, 5, F and 8 described in Example 1 and of Powder G was carried out by laser diffraction on a Malvern Insitec® diffractometer according to ISO standard 13320:2009. The cumulative fraction (percentage) of particles ≦5 μm, ≦10 μm, ≦20 μm and ≦30 μm is shown in the table below. [Table 6] TIFF2025542400000007.tif51170

[0174] It has been found that by applying the method according to the invention it is possible to reduce the amount of fine and ultrafine particles.

Claims

1. A thermoplastic polymer powder comprising particles having a Hausner ratio of 1.30 or less and having a particle size distribution characterized by a span of 1.0 or more.

2. 10. The powder of claim 1, wherein the thermoplastic polymer is a semi-crystalline thermoplastic polymer.

3. 3. The powder according to claim 1 or 2, wherein the thermoplastic polymer is selected from the group consisting of polyamides, vinylidene fluoride homopolymers and copolymers, copolymers comprising polyamide blocks and polyether blocks, thermoplastic polyurethanes, copolymers comprising polyester blocks and polyether blocks, polycarbonates, polystyrenes, polyaryletherketones, polyolefins, and combinations thereof.

4. 4. Powder according to claim 1 , wherein the thermoplastic polymer is at least one polyamide, preferably polyamide 11, polyamide 12 and / or polyamide 6, and / or a copolymer comprising polyamide blocks and polyether blocks, preferably the polyamide blocks being polyamide 6, polyamide 11, polyamide 12, polyamide 6.10, polyamide 10.10 and / or polyamide 10.12 blocks and the polyether blocks being blocks derived from polyethylene glycol, propylene glycol, polytrimethylene glycol and / or polytetrahydrofuran.

5. 5. Powder according to any one of claims 1 to 4, having a Hausner ratio of less than or equal to 1.28, preferably less than or equal to 1.20, more preferably less than or equal to 1.

15.

6. 6. Powder according to any one of claims 1 to 5, comprising particles having a particle size distribution characterized by a span of 1.0 to 2.5, preferably 1.0 to 2.

0.

7. 7. Powder according to any one of claims 1 to 6, wherein the cumulative fraction of particles having a size of less than or equal to 10 μm is less than or equal to 1% by weight, preferably less than or equal to 0.8% by weight, relative to the total weight of the powder, and / or the cumulative fraction of particles having a size of less than or equal to 30 μm is less than or equal to 10% by weight, preferably less than or equal to 5% by weight, more preferentially even less than or equal to 2% by weight, or less than or equal to 1% by weight, relative to the total weight of the powder.

8. 8. The powder according to any one of claims 1 to 7, further comprising at least one additive preferably selected from the group consisting of flow agents, mineral fillers, fibers, polymer powders, dyes, pigments, fire resistant additives, antioxidant stabilizers, light stabilizers, impact modifiers, antistatic agents, flame retardants, and mixtures thereof.

9. 9. Use of a powder according to any one of claims 1 to 8 for building a three-dimensional article, preferably layer by layer, more preferentially by sintering, even more preferentially by electromagnetic radiation mediated sintering.

10. 9. Use of a powder according to any one of claims 1 to 8 for coating a surface, preferably a metal surface.

11. 9. Use of a powder according to any one of claims 1 to 8 for producing an article by rotational molding.

12. 1. A method for preparing a thermoplastic polymer powder, comprising: a) providing a thermoplastic polymer powder; b) heating said powder by an energy source having a temperature between 600 and 10,000°C, preferably between 600 and 8,000°C, more preferentially between 1,000 and 3,000°C; c) preferably spraying said powder; d) cooling the powder; e) recovering the powder; A method comprising:

13. 13. The method of claim 12, wherein the powder prepared is a powder according to any one of claims 1 to 8.

14. 14. The method of claim 12 or 13, wherein the step of providing a thermoplastic polymer powder comprises grinding a thermoplastic polymer or dissolving a thermoplastic polymer in a solvent and precipitating the thermoplastic polymer from the solvent.

15. 1. A method for encapsulating thermoplastic polymer particles with at least one additive, comprising: a) providing thermoplastic polymer particles; b) mixing the thermoplastic polymer particles with at least one additive, preferably selected from the group consisting of flow agents, mineral fillers, fibers, polymer powders, dyes, pigments, fire resistant additives, antioxidant stabilizers, light stabilizers, impact modifiers, antistatic agents, flame retardants, and mixtures thereof, to form a thermoplastic polymer powder; c) heating said powder by an energy source having a temperature between 600 and 10,000°C, preferably between 600 and 8,000°C, more preferentially between 1,000 and 3,000°C; d) optionally spraying the powder; e) cooling the powder; f) recovering the powder; A method comprising:

16. 16. The method of claim 15, wherein the step of providing thermoplastic polymer particles comprises grinding a thermoplastic polymer or dissolving a thermoplastic polymer in a solvent and precipitating the thermoplastic polymer from the solvent.

17. 17. The method according to any one of claims 12 to 16, wherein the cooling is carried out by contacting the powder with cold gas, preferably compressed air, or cold water.

18. 18. The method of any one of claims 12 to 17, wherein the powder is collected in a collection tank or cyclone.

19. 19. The method of any one of claims 12 to 18, further comprising the step of sieving the recovered powder and / or mixing the recovered, optionally sieved, powder with at least one additive, preferably selected from the group consisting of flow agents, mineral fillers, fibers, polymer powders, dyes, pigments, fire resistance additives, antioxidant stabilizers, light stabilizers, impact modifiers, antistatic agents, flame retardants, and mixtures thereof.

20. A three-dimensional article manufactured from a powder according to any one of claims 1 to 8, preferably by layer-by-layer printing, more preferentially by sintering.

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