FILLED POLYARYLETHERKETONE POWDER, METHOD FOR PRODUCING IT AND USE OF IT

Description

technical field

[0001] The invention relates to the field of poly-aryl-ether-ketone(s) powders.

[0002] More specifically, the invention relates to a powder loaded with poly-aryl-ether-ketone(s), a method for manufacturing the powder and its use in a method for manufacturing three-dimensional objects, in particular in a powder sintering process caused by electromagnetic radiation. Previous art

[0003] Polyaryl ether ketones (PAEKs) are well-known high-performance engineering polymers. They can be used in demanding applications involving high temperatures and / or high mechanical and even chemical stresses. They are also suitable for applications requiring excellent fire resistance and low emissions of smoke or toxic gases. Finally, they exhibit good biocompatibility. These polymers are found in fields as diverse as aerospace, offshore drilling, automotive, rail, marine, wind energy, sports, construction, electronics, and medical implants. They can be processed using all thermoplastic manufacturing technologies, such as molding, compression molding, extrusion, spinning, powder coating, and sintering prototyping.

[0004] The processes for building layer-by-layer objects by sintering induced by electromagnetic radiation, particularly infrared and laser radiation, are well known to those skilled in the art. With reference to the Figure 1 The laser sintering device 1 comprises a sintering chamber 10 in which are arranged a feed tray 40 containing the powder to be sintered, a horizontal plate 30 allowing support of the three-dimensional object 80 under construction and a laser 20. The powder is taken from the feed tray 40 and deposited on the horizontal plate 30, forming a thin layer 50 of powder constituting the three-dimensional object 80 under construction.

[0005] A compactor / scraper roller (not shown) ensures the uniformity of the powder layer 50. The powder layer 50, during construction, is heated by infrared radiation 100 to reach a substantially uniform temperature equal to a predetermined construction temperature Tc. In traditional PAEK(s)-based powder sintering construction processes, Tc is generally about 20°C lower than the powder's melting temperature. In some cases, Tc may even be lower. The energy required to sinter the powder particles at various points in the powder layer 50 is then supplied by laser radiation 200 from a laser 20 moving in the (xy) plane, with a geometry corresponding to that of the object. The molten powder re-solidifies, forming a sintered portion 55, while the remainder of the layer 50 remains as unsintered powder 56.Several passes of laser radiation 200 may be necessary in some cases. Next, the horizontal plate 30 is lowered along the (z) axis by a distance corresponding to the thickness of a powder layer, and a new layer is deposited. The laser 20 provides the energy needed to sinter the powder particles into a geometry corresponding to this new slice of the object, and so on. The procedure is repeated until the object 80 has been manufactured. Once the object 80 is complete, it is removed from the horizontal plate 30, and the unsintered powder 56 can be sieved before being returned, if necessary, to the feed bin 40 to serve as recycled powder.

[0006] In order to improve the mechanical properties, in particular to increase the modulus of elasticity, of objects made from poly-aryl-ether-ketone(s) powder, in particular objects made by sintering caused by electromagnetic radiation(s), it is known to add carbon fibers to the poly-aryl-ether-ketone(s) powder.

[0007] Carbon fibers can be mixed with dry polyaryl ether ketone particles ( dry-blend ) .For example, US2018 / 0201783 describes a composition resulting from a dry mixture of polyetherketone-ketone particles with carbon fibers whose median length is strictly greater than the average particle diameter. More specifically, the mixture comprises 85% by weight of polyetherketone-ketone particles having a median diameter of 61.34 µm, measured using a Coulter Counter particle counter according to ISO 13319, and 15% by weight of carbon fibers with a median length L50 of 77 µm and an approximate diameter of 7.1 µm. The mixture is introduced into a high-intensity mixer to partially incorporate at least some of the carbon fibers into the polyetherketone-ketone particles. The dry mixture of poly-ether-ketone-ketone particles with carbon fibers has the advantage of being particularly easy to prepare.

[0008] However, the dry mixing of carbon fibers with poly-aryl-ether-ketone(s) particles presents several disadvantages.

[0009] A first disadvantage is that the three-dimensional objects produced by laser sintering these powders have anisotropic mechanical properties, meaning they differ depending on whether one is viewing them along the "Z" axis, along which the different layers were printed, or along the (XY) plane, in which each layer was printed. This is because carbon fibers tend to align themselves in a preferred direction when passing through the compactor / scraper roller. A second disadvantage is that it is not possible to use a high proportion of carbon fibers in the powder, as this risks compromising its flowability, which is essential for laser sintering.Indeed, since carbon fibers are very difficult to incorporate into polyetherketone-ketone particles, a high proportion of carbon fibers in the composition means that few of them manage to incorporate sufficiently into the polyetherketone-ketone particles. This implies that a majority of the carbon fibers remain free in the composition, thus impairing the powder's flowability. Furthermore, reprocessing the powder—that is, recycling at least some of it after sieving for use in another object construction by laser sintering—is not easily achievable due to the difficulty of maintaining a constant carbon fiber content within the polyetherketone-ketone powder.US2018 / 0201783 indicates a proportion of 5% to 30% by weight of carbon fibers in the dry mix, knowing that to date dry mixes of poly-ether-ketone-ketone particles with carbon fibers available on the market have a proportion of carbon fibers generally not exceeding 15% by weight of composition.

[0010] To ensure that three-dimensional objects produced by laser sintering have substantially isotropic mechanical properties, powders are known in which carbon fibers are incorporated within polyaryl ether ketone particles. For example, US patent application 2005 / 0207931 describes polyaryl ether ketone particles incorporating carbon fibers, with the polyaryl ether ketone forming a matrix and the carbon fibers essentially embedded within the matrix. The "average diameter D50" (measurement method not detailed) is between 20 µm and 150 µm. The average length of the carbon fibers is also between 20 and 150 µm.

[0011] US application 2005 / 0207931 describes three methods for preparing thermoplastic particles incorporating more than 30% by weight of carbon fibers (see variant 3).

[0012] The first described manufacturing method is spray drying ( spray-drying ). This method involves mixing a thermoplastic micropowder with a D50 between 3 µm and 10 µm with carbon fibers in a liquid phase, such as ethanol or a water / ethanol mixture. The suspension is sprayed onto a surface, and then the liquid phase of the suspension is vaporized or evaporated to form a powder.

[0013] The second method involves grinding thermoplastic granules with an initial grain size of 3 mm, into which carbon fibers are already incorporated. Grinding takes place under cryogenic conditions in a mill equipped with pin discs until the particles reach the desired size and are then separated using an air separator.

[0014] The third manufacturing method is spray-melting ( melt-spraying ) .This method involves spraying a mixture of carbon fibers and molten thermoplastic to obtain particles with sizes on the order of a few tens of micrometers.

[0015] These three methods can prove very difficult to implement, especially when the thermoplastic is a polyaryl ether ketone (POE). Even if they could reasonably be implemented with a POE, the resulting POE-laden powder would be very expensive. In particular, the first method appears very difficult to implement due to the complexity and significant cost of obtaining POE particles a few micrometers in size for use in the starting powder. The second method also seems complicated because the presence of carbon fibers in the granules to be ground tends to cause significant abrasion and accelerated mill aging.Furthermore, in the second method, the size of the carbon fibers incorporated into the polyaryl ether ketone particles is controlled by the particle size and generally cannot exceed the particle size. Finally, the third method is also complicated to implement because proper powder production depends on preventing particle agglomeration during spraying, which in particular necessitates an extremely rapid and precise cooling system.

[0016] Consequently, powder compositions comprising a polyaryl ether ketone (PAEK) matrix and carbon fibers essentially incorporated within the matrix are significantly more expensive than dry mixtures of PAEK particles and carbon fibers. Furthermore, the reinforcement achieved in three-dimensional objects is generally less pronounced for those produced by laser sintering PAEK particle compositions incorporating carbon fibers compared to those produced by laser sintering dry mixtures of PAEK particles and carbon fibers. This is primarily due to the fact that in the former case, the size of the carbon fibers is generally controlled by the particle size, whereas in the latter case, the carbon fibers can be considerably longer.

[0017] Therefore, there is a need to develop alternative poly-aryl-ether-ketone(s) loaded powders to improve mechanical properties, in particular to increase the modulus of elasticity, or even the tensile strength, of objects made from these powders, especially objects made by sintering caused by electromagnetic radiation(s).

[0018] There is also a need to develop optimized processes to obtain these charged powders. Objectives of the invention

[0019] The objective of the invention is therefore to propose a charged powder and a method for manufacturing this powder, which overcome at least some of the disadvantages of the prior art.

[0020] One objective of the invention is in particular to offer a filled powder based on poly-aryl-ether-ketone(s) leading to objects having better mechanical properties, in particular a higher modulus of elasticity and breaking strength, than an unfilled powder based on poly-aryl-ether-ketone(s).

[0021] Another objective of the invention is to provide a loaded powder based on poly-aryl-ether-ketone(s) leading to objects whose mechanical properties are substantially isotropic.

[0022] According to some embodiments, one objective is to offer a filled powder that has a relatively low production cost.

[0023] According to some embodiments, an objective is to provide a powder that leads to objects that have similar or even improved mechanical properties compared to poly-aryl-ether-ketone(s) based powders comprising carbon fibers (dry mix with the fibers or incorporated fibers).

[0024] According to some embodiments, an objective is to provide a powder that can be used in a powder sintering process by electromagnetic radiation(s) and that can, if necessary, be easily recycled in one or more subsequent construction(s).

[0025] Another objective of the invention is also to propose a method for manufacturing the powder according to the invention which is simple and has a relatively low cost price. Summary of the invention

[0026] The invention relates to a powder having a volume-weighted particle size distribution, measured by laser diffraction, according to ISO 13320:2009, with a median diameter D50 ranging from 40 to 120 micrometers.

[0027] The powder comprises at least one polyaryl ether ketone (PAEK) and at least one filler, in which: said at least one polyaryl ether ketone forms a matrix incorporating said at least one filler, and, said filler has a Stokes equivalent spherical diameter distribution, measured by X-ray gravity sedimentation in a liquid, according to ISO 13317-3:2001, with a median diameter of 50 less than or equal to 5 micrometers.

[0028] The term "D50" refers to the value of the powder particle diameter at which the volume-weighted cumulative particle diameter distribution function equals 50%. "D50" is measured by laser diffraction according to ISO 13320:2009, for example on a Malvern Mastersizer 2000® diffractometer.

[0029] The term "D'50" refers to the value of the diameter of the charge particles such that the cumulative distribution function of particle diameters, weighted by volume, is equal to 50%. "D'50" is measured by laser diffraction according to ISO 13320:2009, for example on a Malvern Mastersizer 2000 ® diffractometer.

[0030] The term "d'50" refers to the value of the diameter of the charge particles such that the cumulative distribution function of equivalent spherical diameters of Stokes is equal to 50%. "d'50" is measured by gravity sedimentation in a liquid according to ISO 13317-3:2001, for example in a Sedigraph III Plus ® instrument.

[0031] The ISO 9276 standard is used for mathematical and statistical modeling to calculate the particle size distribution.

[0032] For charge particles of approximately spherical shape, D'50 and d'50 are approximately equal. For charge particles of non-spherical shape, particularly for flattened and / or elongated particles that can be described by a characteristic length and a characteristic thickness, a shape coefficient C is defined by the following formula: C = D ′ 50 − d ′ 50 d ′ 50

[0033] The term "Z-axis" refers to the direction in which the different layers are printed in a layer-by-layer printing process using electromagnetic radiation and powder sintering. Conversely, (XY) refers to the plane in which each layer is printed.

[0034] The inventors of the present invention have surprisingly observed that the claimed powder makes it possible to manufacture three-dimensional objects by a layer-by-layer object-building process using electromagnetic radiation-induced sintering, possessing superior mechanical properties compared to those made from uncharged polyaryl ether ketone(s)-based powder. Indeed, the powder, comprising PAEK(s) and incorporating a filler with a d50 sufficiently lower than the D50 of the powder, makes it possible, in particular, to obtain three-dimensional objects by laser sintering with greater rigidity and / or greater fracture toughness.The inventors were also able to demonstrate that, in certain embodiments, the powder according to the invention made it possible to manufacture three-dimensional objects by a layer-by-layer construction process by sintering caused by electromagnetic radiation, possessing mechanical properties (in particular resistance to breakage and elongation at break) of a similar order, or even superior, to those of objects obtained from powder based on poly-aryl-ether-ketone(s) and carbon fibers (dry fiber mixture or incorporation of fibers within a matrix).

[0035] Furthermore, the mechanical properties of the three-dimensional objects made from the powder according to the invention are isotropic or quasi-isotropic, that is to say equivalent in all directions of space.

[0036] In some embodiments, the filler has a particle size distribution with a median diameter of 50 less than or equal to 2.5 micrometers. In some embodiments, the mass ratio of the filler to said at least one PAEK is from 1:9 to 1:1.

[0037] For a mass ratio below 1:9, the gain in mechanical properties, particularly the increase in the modulus of elasticity, of an object made from the powder is generally not substantial compared to an object made from unfilled powder. For a mass ratio above 1:1, the object made from the powder is generally too brittle. Preferably, the mass ratio of the filler to said at least one PAEK is from 1:4 to 3:7.

[0038] According to certain embodiments, said at least one PAEK and said at least one charge together represent at least 60%, or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 92.5%, or at least 95%, or at least 97.5%, or at least 98%, or at least 98.5%, or at least 99% or at least 99.5%, or 100% of the total weight of the powder.

[0039] According to some embodiments, PAEK is a statistical copolymer of polyetherketone-ketone (PEKK), essentially consisting of, preferably consisting of, a terephthalic motif and an isophthalic motif, the terephthalic motif (T) having the formula: the isophthalic motif (I) having the formula:

[0040] In some embodiments, the mass percentage of terephthalic repeats relative to the sum of terephthalic and isophthalic repeats is 55 to 65%. Preferably, the mass percentage of terephthalic repeats relative to the sum of terephthalic and isophthalic repeats is approximately 60%. In some embodiments, at least one PAEK is a copolymer, essentially composed of, preferably composed of: motif(s) of formula: -Ph-O-Ph-O-Ph-C(O)- and, motif(s) of formula: -Ph-O-Ph-Ph-O-Ph-C(O)-, in which Ph represents a phenylene group and -C(O)- a carbonyl group, each of the phenylenes being independently able to be of ortho, meta or para type, preferably of meta or para type.

[0041] In some embodiments, the filler is a mineral filler. This filler may preferably be selected from the group consisting of: calcium carbonate, silica, talc, wollastonite, mica, kaolin, and mixtures thereof. Even more preferably, this filler is talc. Talc has the advantage of being inexpensive and providing useful reinforcing properties for an object made from a powder according to the invention.

[0042] According to certain embodiments, said load has a shape coefficient C greater than or equal to 2, said shape coefficient C being defined by the following formula: C = D ′ 50 − d ′ 50 d ′ 50 ; in which, D'50 denotes the median diameter of the charge particles, volume weighted and measured according to ISO 13320:2009 and, in which, d'50 denotes the median spherical Stokes equivalent diameter of the charge particles, measured by X-rays with gravity sedimentation in a liquid, according to ISO 13317-3:2001.

[0043] The present invention also relates to a powder manufacturing process comprising the steps of: the supply of at least one polyaryl ether ketone (PAEK) and the supply of at least one filler, said at least one filler having a Stokes spherical equivalent diameter distribution, measured by X-ray gravity sedimentation in a liquid, according to ISO 13317-3:2001, with a median diameter of 50 less than or equal to 5 micrometers; the extrusion-granulation of said at least one polyaryl ether ketone (PAEK) with said at least one filler to form granules; and, the grinding of the granules to obtain a powder having a volume-weighted particle size distribution, measured by laser diffraction, according to ISO 13320:2009, with a median diameter D50 ranging from 40 to 120 micrometers.

[0044] The inventors of the present invention have observed that, surprisingly, grinding PAEK-based granules incorporating a filler with a D50 of 5 micrometers or less facilitates grinding compared to PAEK-based granules incorporating carbon fibers. Selecting a filler with a D50 of 5 micrometers or less makes it easy to obtain powders with a D50 ranging from 40 to 120 micrometers. The grinding time is therefore short. Furthermore, PAEK-based granules incorporating a filler with a D50 of 5 micrometers or less are generally much less abrasive during grinding than PAEK-based granules incorporating carbon fibers of the prior art. The mill is therefore not subjected to excessive abrasion.According to some embodiments, the process further includes a heat treatment of the granules before the grinding step to allow the crystallization, at least partial, of said at least PAEK of the powder.

[0045] The present invention also relates to a method for building layer-by-layer objects by sintering induced by electromagnetic radiation, in which a powder according to the invention is used. In other words, the invention also relates to the use of the powder described above in a method for building layer-by-layer objects by sintering induced by at least one electromagnetic radiation.

[0046] Finally, the present invention relates to any object obtainable by the layer-by-layer object construction process by sintering induced by electromagnetic radiation(s) in which the powder is used. This object is characterized in that it has, in at least one direction, a tensile elastic modulus greater than or equal to 7 GPa, on a type 1BA test specimen, at 23°C, with a through-spin speed of 1 mm / min, according to ISO 527-2:2012. Since the mechanical properties of the object are nearly isotropic, it generally has a tensile elastic modulus greater than or equal to 7 GPa in all spatial directions, particularly along the (XY) plane and the Z-axis. Brief description of the figures

[0047] There Figure 1 schematically represents a device enabling the implementation of a process for constructing a three-dimensional object layer-by-layer by sintering in which the powder according to the invention can be used. Detailed description of the invention Polyaryl ether ketones

[0048] The polyaryl ether ketone(s) (PAEK(s)) of the powders according to the invention comprises the following formula motifs: (-Ar-X-) and (-Ar 1 -Y-), in which: Ar and Ar 1 each denote a divalent aromatic radical; Ar and Ar 1 may preferably be chosen from 1,3-phenylene, 1,4-phenylene, 4,4'-biphenylene, 1,4-naphthylene, 1,5-naphthylene and 2,6-naphthylene; X denotes an electron-withdrawing group; it may preferably be chosen from the carbonyl group and the sulfonyl group; Y denotes a group chosen from an oxygen atom, a sulfur atom, an alkylene group, such as -(CH) 2 - and isopropylidene.

[0049] In these motifs X and Y, at least 50%, preferably at least 70% and more particularly at least 80% of the X groups are a carbonyl group, and at least 50%, preferably at least 70% and more particularly at least 80% of the Y groups represent an oxygen atom.

[0050] According to a preferred embodiment, 100% of the X groups denote a carbonyl group and 100% of the Y groups represent an oxygen atom.

[0051] Advantageously, the PAEK(s) of the powders can / may be chosen from: a polyether-ether-ketone, also called PEKK; a PEKK comprises one or more motifs with the formula: -Ph-O-Ph-C(O)-Ph-C(O)- ; a polyether-ether-ketone, also called PEEK; a PEEK comprises one or more motifs with the formula: -Ph-O-Ph-O-Ph-C(O)- ; a polyether-ether-ketone, also called PEK; a PEK comprises one or more motifs with the formula: -Ph-O-Ph-C(O)- ; a polyether-ether-ketone, also called PEEKK; a PEEKK comprises one or more motifs with the formula: -Ph-O-Ph-O-Ph-C(O)- Ph-C(O)- ; a polyether-ether-ether-ketone, also called PEEEK; a PEEEK comprises one or more motifs of the formula: -Ph-O-Ph-O-Ph-O- Ph-C(O)- ; a poly-ether-diphenyl-ether-ketone also called PEDEK; a PEDEK comprises one or more motifs of the formula: a PEDEK comprises one or more motifs of the formula -Ph-O-Ph-Ph-O-Ph-C(O)- ; their mixture(s) ; and, their copolymer(s).

[0052] In the formulas of the motifs in the list above, Ph represents a phenylene group and -C(O)- a carbonyl group, each of the phenylenes being independently able to be of ortho (1-2), meta (1-3) or para (1-4) type, preferably of meta or para type.

[0053] In addition, defects, terminal groups and / or monomers may be incorporated in very small quantities into the polymers as described in the list above, without affecting their performance.

[0054] In certain embodiments, said at least one PAEK is a PEKK. The PEKK may be a copolymer essentially composed of, preferably composed of, "type I" (isophthalic-type) units, of formula: (I); and, "Type T" (terephthalic) motifs, with the following formula:

[0055] The mass proportion of T motifs relative to the sum of the T and I motifs of PEKK(s) can vary from 0 to 5%; or from 5 to 10%; or from 10 to 15%; or from 15 to 20%; or from 15 to 20%; or from 20 to 25%; or from 25 to 30%; or from 30 to 35%; or from 35 to 40%; or from 40 to 45%; or from 45 to 50%; or from 50 to 55%; or from 55 to 60%; or from 60 to 65%; or from 65 to 70%; or from 70 to 75%; or from 75 to 80%; or from 80 to 85%; or from 85 to 90%; or from 90 to 95%; or 95 to 100%. The choice of the mass proportion of T motifs relative to the sum of T and I motifs is one of the factors that allows adjusting the melting temperature and crystallization rate of PEKK at a given temperature. A given mass proportion of T motifs relative to the sum of T and I motifs can be obtained by adjusting the respective concentrations of the reactants during polymerization, in a manner known per se.

[0056] According to advantageous embodiments, the sum of terephthalic and isophthalic motifs in PEKK is 55 to 65%; preferably the mass percentage of terephthalic motif relative to the sum of terephthalic and isophthalic motifs is about 60%.

[0057] In certain embodiments, said at least one PAEK is a PEEK-PEDEK copolymer. The PEEK-PEDEK copolymer may essentially consist of, preferably consist of, repeating units of the formula: and, reasons for the formula:

[0058] The molar proportion of motif (III) relative to the sum of motifs (III) and (IV) of PEEK-PEDEK(s) may vary from 0 to 5%; or from 5 to 10%; or from 10 to 15%; or from 15 to 20%; or from 15 to 20%; or from 20 to 25%; or from 25 to 30%; or from 30 to 35%; or from 35 to 40%; or from 40 to 45%; or from 45 to 50%; or from 50 to 55%; or from 55 to 60%; or from 60 to 65%; or from 65 to 70%; or from 70 to 75%; or from 75 to 80%; or from 80 to 85%; or from 85 to 90%; or 90 to 95%; or 95 to 100%. The choice of the mole proportion of motif (III) relative to the sum of motifs (III) and (IV) is one of the factors that allows adjusting the melting temperature and crystallization rate of PEEK-PEDEK at a given temperature. A given mole proportion of motif (III) relative to the sum of motifs (III) and (IV) can be obtained by adjusting the respective concentrations of the reactants during polymerization, in a manner known per se.

[0059] The viscosity index of the PAEK(s), measured in solution at 25°C in an aqueous solution of sulfuric acid at 96% by mass according to ISO 307: 2019 can be from 0.65 dl / g to 1.15 dl / g, preferably from 0.70 dl / g to 1.05 dl / g, and even more preferably from 0.70 dl / g to 0.92 dl / g. Charges

[0060] The at least one charge in the powder according to the invention has a Stokes equivalent spherical diameter distribution, measured by X-ray with gravity sedimentation in a liquid, according to ISO 13317-3:2001, with a median diameter of 50 less than or equal to 5 micrometers.

[0061] The charge may have a particle size distribution with a median diameter of 50 less than or equal to 2.5 micrometers. In some cases, the charge may have a median diameter of 50 less than or equal to 2 micrometers, or less than or equal to 1.5 micrometers, or even less than or equal to 1 micrometer. The median diameter of 50 of the charge is generally not less than 0.1 micrometer.

[0062] According to some embodiments, the median diameter of 50 is 0.1 to 5.0 micrometers, or 0.25 to 4.0 micrometers, or 0.5 to 3.0 micrometers. The median diameter of 50 can in particular be 0.1 to 0.5 micrometers, or 0.5 to 1.0 micrometers, or 1.0 to 1.5 micrometers, or 1.5 to 2.0 micrometers, or 2.0 to 2.5 micrometers, or 2.5 to 3.0 micrometers, or 3.0 to 3.5 micrometers, or 3.5 to 4.0 micrometers, or 4.0 to 4.5 micrometers, or 4.5 to 5.0 micrometers.

[0063] Advantageously, the filler is a mineral filler.

[0064] Advantageously, the charge is a reinforcing charge, that is to say, enabling the improvement of the rigidity, in particular the elastic modulus in tension, and / or the breaking strength of said at least one polyaryl ether ketone (PAEK).

[0065] The filler may include calcium carbonate (calcite).

[0066] The filler may also include silica. Specifically, it may be pure silica (SiO2), synthetic silica, quartz, or diatomaceous earth. Talc may also be included.

[0067] The charge may also include wollastonite.

[0068] The filler may ultimately include a clay or an aluminosilicate. Specifically, it may be kaolin, slate flour, vermiculite, or mica.

[0069] The filler is advantageously talc. Talc has the advantage of being inexpensive and providing useful reinforcing properties for an object made from a powder according to the invention.

[0070] The load is preferably non-spherical. It can be characterized by its shape coefficient C, C being advantageously greater than or equal to 2. The shape coefficient C is generally not greater than 20. Powder manufacturing process

[0071] In the powder manufacturing process according to the invention, the poly-aryl-ether-ketone(s) and the filler(s) are mixed and then extruded.

[0072] According to a first embodiment, at least one filler and at least one polyaryl ether ketone are mixed dry and introduced at the level of the main hopper of the extruder.

[0073] According to a second, more advantageous embodiment, at least one polyaryl ether ketone is introduced at the main hopper, while at least one filler is introduced by lateral feeding and added to the molten polyaryl ether ketone. This has the advantage of preventing the filler(s) from being excessively damaged during their passage through the extruder.

[0074] Any extruder suitable for extruding high-melting-point polymers can be used. Furthermore, a person skilled in the art can adapt the extrusion conditions according to the polymer being used. One example of such an extruder is a Labtech twin-screw extruder with a screw diameter of 26 mm and an L / D ratio of 40. The extruded mixture is subdivided to form granules.

[0075] The granules are then optionally heat-treated to increase the crystallinity of the polyaryl ether ketone(s). High granule crystallinity facilitates the subsequent grinding step. Advantageously, the PAEK fraction in the powder has an enthalpy of fusion, measured during the first heating at a rate of 20°C / min according to ISO 11357-2:2013, ranging from 20 to 50 J / g(PAEK), preferably ranging from 25 to 40 J / g(PAEK).

[0076] The heat treatment is advantageously carried out at a temperature well below the melting point of the powder. According to a variant in which the powder is a PEKK-based powder with a mass percentage of terephthalic motifs relative to the sum of terephthalic and isophthalic motifs of 55 to 65%, the heat treatment can be carried out at a temperature of 180°C to 220°C.

[0077] The granules are then ground into a powder with a particle size distribution and a median diameter D50 ranging from 40 to 120 micrometers. The granules according to the invention are more brittle than PAEK granules incorporating carbon fibers (at the same volumetric filler content): the grinding step is therefore simplified. Furthermore, PAEK granules incorporating a filler, advantageously talc, and having a D50 of 5 micrometers or less are generally much less abrasive during grinding than PAEK granules incorporating carbon fibers. Grinding can be carried out at a temperature below -20°C, preferably below -40°C, by cooling with liquid nitrogen, liquid carbon dioxide, dry ice, or liquid helium.The crusher used is advantageously a pin mill, particularly a counter-rotating pin mill, or an impact crusher, such as a hammer mill, or even a vortex mill. The crusher can be equipped with a screen onto which the crushed particles are sent, the particles passing through the screen being of the desired size. The particles retained by the screen can be returned to the crusher for further grinding. Powders

[0078] The mass ratio of at least one filler to at least one PAEK can be from 1:9 to 1:1. For a mass ratio less than 1:9, the gain in mechanical properties, particularly the increase in the modulus of elasticity, of an object made from the powder is generally not substantial compared to an object made from unfilled PAEK powder. For a mass ratio greater than 1:1, the object made from the powder is generally too brittle. The mass ratio of at least one filler to at least one PAEK is advantageously from 1:4 to 3:7.

[0079] The mass ratio of at least one charge to at least one PAEK can also be from 3:7 to 2:3, or even from 2:3 to 1:1.

[0080] The PAEK(s) and the charge(s) together represent at least 60%, or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 92.5%, or at least 95%, or at least 97.5%, or at least 98%, or at least 98.5%, or at least 99% or at least 99.5%, or 100% of the total weight of the powder.

[0081] In addition to the PAEK(s) and the filler(s), the powder may include another polymer not belonging to the PAEK family, in particular other thermoplastic polymers.

[0082] The powder may also contain additives. Examples of additives include flow agents, stabilizing agents (light, particularly UV, and heat), optical brighteners, colorants, pigments, and energy-absorbing additives (including UV absorbers). Additives generally constitute less than 5% by weight of the total powder weight, and preferably less than 1% by weight. Use of powders

[0083] The powders according to the invention can be used in many applications, including the non-exhaustive list below.

[0084] The powders according to the invention can be used in layer-by-layer object construction processes by sintering induced by electromagnetic radiation. A sintering process using infrared and laser radiation is illustrated by the figure 1 and has already been described in the section dealing with prior art.

[0085] The powders according to the invention can also be used in processes for coating metallic surfaces. Various processes can be used to ultimately obtain a coating on metal parts. One example is fluidized bed immersion, in which the metal part is heated and then immersed in a fluidized bed of powder. Electrostatic powder coating (charged powder applied to a grounded metal part) is also possible; in this case, a post-treatment heat treatment is performed to create the coating. An alternative is to apply the powder to a pre-heated part, thus eliminating the need for post-treatment heat treatment. Finally, flame powder coating is possible, in which the molten powder is sprayed onto a metal part, possibly preheated.

[0086] The powders according to the invention can also be used in powder compression processes. These processes are generally used to produce thick parts. In these processes, the powder is first loaded into a mold, compacted, and then melted to form the part. Finally, appropriate cooling is carried out (often quite slow) to overcome internal stresses within the part. Experimental data

[0087] The powders in the examples below were manufactured by compounding (extrusion-granulation) of different compositions, heat treatment and then grinding.

[0088] The compounding process was carried out on a Labtech twin-screw extruder with a screw diameter of 26 mm and an L / D ratio of 40, with a flat temperature profile at 350°C and a screw speed of 400 rpm. Granules of approximately 2 mm in length were obtained.

[0089] In the case of manufacturing filled powders (carbon fibers or talc), the fillers are introduced during compounding by lateral feeding. The resulting granules are described as "filled".

[0090] The granules were then heat-treated for 9 hours at 180°C.

[0091] Finally, the heat-treated granules were ground in a Mikropull 2DH ® cryogenic hammer mill cooled by liquid nitrogen, the mill also being equipped with a screen with 500 micron round holes. Example 1 (comparative)

[0092] The first composition used is a polyether-ketone-ketone having a mass proportion of T motif relative to the sum of T and I motifs of 60%, having a viscosity index of 0.75 dl / g at 25°C, in an aqueous solution of 96% by mass sulfuric acid, according to ISO 307:2019 applied to a PAEK. This polyether-ketone-ketone is marketed by ARKEMA under the name Kepstan®.

[0093] The granules obtained with the composition according to example 1 could be ground until a D50, measured using a Malvern Mastersizer 2000 ®< diffractometer, of 500 microns was obtained. Example 2 (comparative)

[0094] The second composition used consists of poly-ether-ketone-ketone according to example 1 and carbon fibers, the carbon fibers representing 23% by weight of the composition.

[0095] The carbon fibers used were Tenax®-A fibers, type "HT M100", i.e., with fiber lengths between 60 micrometers and 100 micrometers.

[0096] The granules obtained with the composition according to example 2 could be ground until a D50, measured using a Malvern Mastersizer 2000 ®< diffractometer, of 160 microns was obtained. Example 3 (according to the invention)

[0097] The third composition used consists of poly-ether-ketone-ketone according to example 1 and Jetfine ®< 0.7C talc, marketed by the company IMERYS, the talc representing 30% by weight of the composition (in order to ensure a volumetric proportion of filler equivalent to that of example 2).

[0098] Jetfine ®< 0.7C talc has a d'50, measured on Sedigraph III Plus ®< , of 0.7 microns and a D'50, measured on a Malvern Mastersizer 2000 ®< diffractometer , of 2.5 microns, i.e. a form coefficient C equal to: 2.6.

[0099] The granules obtained with the composition according to example 3 could be ground until a D50, measured using a Malvern Mastersizer 2000 ®< diffractometer, of 120 microns was obtained. Example 4 (according to the invention)

[0100] The third composition used consists of poly-ether-ketone-ketone according to example 1 and talc “Steaplus ®< HAR T77” marketed by the company IMERYS, the talc representing 30% by weight of the composition (in order to ensure a volumetric proportion of filler equivalent to that of example 2).

[0101] Steaplus ®< HAR T77 talc has a d'50, measured on Sedigraph III Plus ®< , of 2.2 microns and a D'50, measured on a Malvern Mastersizer 2000 ®< diffractometer , of 10.5 microns, i.e. a form coefficient C equal to: 3.8.

[0102] The granules obtained with the composition according to example 4 could be ground until a D50, measured using a Malvern Mastersizer 2000 ®< diffractometer, of 110 microns was obtained.

[0103] The results of grinding powders according to examples 3 and 4 (according to the invention) compared with the results of grinding powders according to examples 1 and 2 (comparative examples) show that the grinding of PEKK granules incorporating a talc filler having a d50 less than or equal to 5 micrometers is facilitated compared with unfilled PEKK granules or PEKK granules incorporating carbon fibers at the same volumetric filler rate. Example 6 (comparative)

[0104] Type 1BA test specimens, according to ISO 527-2:2012, were fabricated by laser sintering of 6002 PL® powder, marketed by ARKEMA, in an EOS P800® printer, marketed by EOS. The powder has a D50 of 50 µm, measured using a Malvern Mastersizer 2000® diffractometer, and a viscosity index of 0.96 dl / g at 25°C, in a 96% wt. aqueous sulfuric acid solution, according to ISO 307:2019 applied to a PAEK. Type 1BA test specimens were built along the X, Y, and Z axes at a build temperature of 290°C and with a laser energy for sintering of 28 mJ / mm².

[0105] Regardless of the construction axis of the specimens in the laser sintering machine, a tensile elastic modulus of 4 GPa was measured at 23°C, with a traverse speed of 1 mm / min, according to ISO 527-2: 2012, using an MTS 810 ®< device, marketed by MTS Systems Corporation, equipped with a mechanical extensometer. Example 7 (according to the invention)

[0106] Type 1BA test specimens, according to ISO 527-2:2012, were manufactured by powder injection according to example 3, with a feed temperature of 320°C, a screw outlet temperature of 340°C, a mold temperature of 80°C and a cycle time of no more than 1 minute.

[0107] A tensile elastic modulus of 9 GPa was measured, at 23°C, with a traverse speed of 1 mm / min, according to ISO 527-2: 2012, using an MTS 810 ®< device, marketed by MTS Systems Corporation, equipped with a mechanical extensometer.

[0108] It is generally accepted that the elastic modulus value obtained for a specimen manufactured by injection molding is equal to, or even less than, the value that would be determined for a specimen manufactured by laser sintering. Thus, if the specimen had been manufactured by laser sintering, it would certainly have a tensile elastic modulus of at least 9 GPa. Example 8 (according to the invention)

[0109] Type 1BA test specimens, according to ISO 527-2: 2012, were manufactured by powder injection according to example 4, following the same protocol as example 7.

[0110] A tensile elastic modulus of 9 GPa was also measured, following the same protocol as in example 7.

[0111] Similarly, if the test specimen had been manufactured by laser sintering, it would certainly have a tensile elastic modulus of at least 9 GPa.

[0112] The results of the mechanical tests according to examples 7 and 8 (according to the invention) compared with the results of the mechanical tests according to example 6 (comparative example) show that the mechanical properties of objects obtained from PEKK powders incorporating a talc filler having a d50 less than or equal to 5 micrometers are superior to those obtained from unfilled PEKK powders.

[0113] The results of the mechanical tests according to Examples 7 and 8 further suggest that the mechanical properties of objects obtained from PEKK powders incorporating a talc filler with a δµm particle size less than or equal to 5 micrometers would be of the same order of magnitude, or even superior, to those of objects obtained from powders filled with carbon fibers, when compared at the same volumetric filler content. Indeed, the specification sheet for the HT-23® material, marketed by Advanced Laser Materials, indicates a tensile elastic modulus along X of 6.5 GPa, along Y of 6.4 GPa, and along Z of 5.8 GPa, values ​​measured according to ASTM D638. HT-23 ®< is a poly-ether-ketone-ketone powder incorporating 23% carbon fibers and intended for laser sintering applications in printers such as the EOS P 500 ®< and EOS P 810 ®<, marketed by the EOS company.

Claims

1. Powder having a volume-weighted particle size distribution, measured by laser diffraction, according to the standard ISO 13320: 2009, with a median diameter D50 ranging from 40 to 120 micrometres, comprising at least one polyaryl ether ketone (PAEK) and at least one filler, in which: - said at least one polyaryl ether ketone forms a matrix incorporating, at least partly, said at least one filler, and - said filler has a Stokes equivalent spherical diameter distribution, measured by X-ray with gravitational liquid sedimentation, according to the standard ISO 13317-3: 2001, with a median diameter d'50 of less than or equal to 5 micrometres.

2. Powder according to Claim 1, in which said filler has a Stokes equivalent spherical diameter distribution with a median diameter d'50 of less than or equal to 2.5 micrometres.

3. Powder according to either one of Claims 1 and 2, in which the mass ratio of said filler to said at least one PAEK is from 1:9 to 1:1; preferentially, the mass ratio of said mineral filler to said at least one PAEK is from 1:4 to 3:7.

4. Powder according to any one of Claims 1 to 3, in which said at least one PAEK and said at least one filler together represent at least 60%, or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 92.5%, or at least 95%, or at least 97.5%, or at least 98%, or at least 98.5%, or at least 99% or at least 99.5% or 100% of the total weight of the powder.

5. Powder according to any one of Claims 1 to 4, in which said at least one PAEK is a statistical copolymer of polyether ketone ketone (PEKK), consisting essentially of, preferentially consisting of, a terephthalic unit and an isophthalic unit, the formula of the terephthalic unit (T) being: the formula of the isophthalic unit (I) being:

6. Powder according to Claim 5, in which the mass percentage of terephthalic units relative to the sum of the terephthalic and isophthalic units is from 55% to 65%; preferentially, the mass percentage of terephthalic units relative to the sum of the terephthalic and isophthalic units is about 60%.

7. Powder according to any one of Claims 1 to 4, in which said at least one PAEK is a copolymer consisting essentially of, preferentially consisting of: - unit(s) of formula: -Ph-O-Ph-O-Ph-C(O)-; and - unit(s) of formula: -Ph-O-Ph-Ph-O-Ph-C(O)-; in which Ph represents a phenylene group and -C(O)-represents a carbonyl group, each of the phenylenes possibly being, independently, of the ortho, meta or para type, preferentially of meta or para type.

8. Powder according to any one of Claims 1 to 7, in which said filler is a mineral filler; said filler preferentially being chosen from the group consisting of: calcium carbonate, silica, talc, wollastonite, mica, kaolin, and a mixture thereof; said filler more preferably being a talc.

9. Powder according to any one of Claims 1 to 8, in which said filler has a shape coefficient C of greater than or equal to 2, said shape coefficient C being defined by the following formula: C = D ′ 50 − d ′ 50 d ′ 50 ; in which D'50 denotes the volume-weighted median diameter of the filler particles, measured according to the standard ISO 13320: 2009 and in which d'50 denotes the median Stokes equivalent spherical diameter of the filler particles, measured by X-ray with gravitational liquid sedimentation, according to the standard ISO 13317-3: 2001.

10. Powder manufacturing process comprising the steps consisting in: - supplying at least one polyaryl ether ketone (PAEK) and supplying at least one filler, said at least one filler having a Stokes equivalent spherical diameter distribution, measured by X-ray with gravitational liquid sedimentation, according to the standard ISO 13317-3: 2001, with a median diameter d'50 of less than or equal to 5 micrometres; - extrusion-granulation of said at least one polyaryl ether ketone (PAEK) with said at least one filler so as to form granules; and - milling of the granules to obtain a powder having a particle size distribution, measured by laser diffraction, according to the standard ISO 13320: 2009, with a median diameter D50 ranging from 40 to 120 micrometres.

11. Process according to Claim 10, also comprising: - the heat treatment of the granules before the milling step to enable at least partial crystallization of said at least PAEK.

12. Process for the layer-by-layer construction of objects by electromagnetic radiation-mediated sintering, in which a powder according to any one of Claims 1 to 10 is used.

13. Object which may be obtained via the process according to Claim 12, characterized in that it has, in at least one direction, a tensile elastic modulus of greater than or equal to 7 GPa, on a specimen of 1BA type, at 23°C, with a travelling speed of 1 mm / minute, according to the standard ISO 527-2: 2012.