Powder mixture

Abstract

The invention relates to a dry powder mixture comprising: a poly-aryl ether ketone-based powder having a volume-weighted particle size distribution, measured by laser diffraction, according to ISO 13320: 2009, such that the median diameter D50 is such that D50 ≤ 300 μm, and a nucleating filler in powder form, the nucleating filler being selected from a silicate, a carbon material having a BET specific surface area of greater than or equal to 200 g / m2, or a mixture thereof, the nucleating filler representing from 0.1% to 2% by weight, relative to the total weight of powder based on poly-aryl ether ketone and nucleating filler.

Description

[0001] Description

[0002] Title: Powder Mix

[0003] Technical field

[0004] The invention relates to the field of poly-aryl-ether-ketone(s) powders.

[0005] More particularly, the invention relates to a formulation in powder form based on poly-aryl-ether-ketone(s), which can in particular be used for layer-by-layer sintering caused by electromagnetic radiation(s) of a three-dimensional object.

[0006] Prior art

[0007] Polyaryl ether ketones (PAEKs) are well-known high-performance engineering polymers. They can be used for applications requiring high temperature and / or mechanical or even chemical constraints. They can also be used for applications requiring excellent fire resistance and low smoke or toxic gas emissions. Finally, they exhibit good biocompatibility. These polymers are found in fields as diverse as aeronautics and space, offshore drilling, automotive, rail, marine, wind, sports, construction, electronics, and medical implants.

[0008] Notwithstanding these advantageous properties, it is sometimes necessary to formulate poly-aryl-ether-ketones in order to meet specific specifications. Thus, one may seek to formulate a composition making it possible to obtain more ductile objects to accommodate new modes of use, with for example a possibility of greater traction and / or bending, without causing the object to break. One may in particular seek to formulate a composition based on poly-aryl-ether-ketone(s) to increase its deformation at break and / or to increase its stress at break, compared to the same unformulated compositions.

[0009] The need to provide such formulated compositions exists in particular for methods of manufacturing articles using compositions in powder form. An example of a method, which is detailed in particular later in the present application, is a method of constructing layer-by-layer objects by sintering caused by electromagnetic radiation(s). Other examples of methods requiring a powder composition are the coating, for example of metals, from a powder, powder compression molding, powder compression-transfer molding, or the impregnation of fibers with a resin powder for the manufacture of semi-finished products, the powder being able to be used in a fluidized bed or dispersed in an aqueous solution.

[0010] It is known that the addition of fillers to a polymer composition influences in particular the crystallization and / or the microstructure of this composition. The nature of the filler as well as the proportion in which the latter is additivated can make it possible to vary certain targeted properties, as shown by several examples below from the prior art.

[0011] Application US7790841 discloses, for example, thermoplastic compositions with nanoparticles, the nanoparticles making it possible to increase the crystallization rate, the crystallinity rate, and the density of the composition. Examples include blends obtained by melt-blending polyetherketoneketone and silica. Example 1a of US7790841 discloses, in particular, the introduction of 1-2% wt of hydrophilic silica (Aerosil® R150) or hydrophobic silica (Aerosil® R202). This patent application does not disclose a formulation in powder form.

[0012] According to another aspect, it is known that the addition of a small amount of hydrophilic silica in dry mixing with a PEKK powder makes it possible to obtain a good compromise between the flowability of the powder and its coalescence at the time of sintering. Application US2016333190 exemplifies in particular a dry mixture of polyetherketoneketone powder and 0.2% by weight of hydrophilic silica (CAB-O-Sil® M-5). However, this application does not study the influence of the hydrophilic silica on the crystallization and / or the microstructure of the sintered object.

[0013] Application U S20210403652 discloses compositions for laser sintering of powders comprising a polymer and an additive, the additive being a carbon black or graphite. The objective here is to identify additives which do not modify either the crystallinity or the crystallization of the polymer. In particular, compositions of dry mixtures of polyamide powders and 0.09 wt% of carbon black or graphite are exemplified. The object obtained by sintering from these powder mixtures has spherulites of the same size (see Figures 7 and 8) as those of the object sintered from non-additive powder (see Figure 6), of the order of 20 μm.

[0014] Finally, it is known from application WO2021069833 that the compounding of granules of a composition of PAEK and a certain quantity of talc makes it possible to make the granules more fragile than granules made of PEKK. These granules can be ground into a powder suitable for a laser sintering process. Objects sintered with the powder thus formulated have the advantage of having a higher elastic modulus than those sintered with an unformulated powder. Examples include PEKK powders comprising 30% by weight of talc, the PEKK forming a matrix incorporating the talc.

[0015] None of the formulations of the prior art meet the aforementioned needs. The present invention thus proposes to provide a formulation in powder form based on poly-aryl-ether-ketone(s), with additives, allowing the manufacture of more ductile objects.

[0016] Objective of the invention

[0017] The objective of the invention is to provide an additive-containing powder composition making it possible to manufacture objects having a greater elongation at break and / or a greater stress at break in a process using powders, for example a process for constructing layer-by-layer objects by sintering caused by electromagnetic radiation(s), compared to a non-additive composition.

[0018] Another objective, at least according to certain embodiments, is to provide such an additive powder composition having properties similar to a non-additive composition in terms of warping when it is used for the manufacture of an object.

[0019] Another objective is, at least according to certain embodiments, to provide an additive-containing powder composition which is easy to implement technically, and preferably has a low additional cost. Summary of the invention

[0020] The invention relates to a dry powder mixture comprising a poly-aryl-ether-ketone(s)-based powder having a volume-weighted particle size distribution, measured by laser diffraction, according to ISO 13320: 2009, such that the median diameter D50 is such that D50 < 300 pm, and a nucleating filler in powder form. The nucleating filler in powder form is selected from a silicate, a carbonaceous material having a BET specific surface area greater than or equal to 200 g / m 2 , or their mixture. The nucleating charge represents from 0.1% to 2% by weight, relative to the total weight of powder based on poly-aryl-ether-ketone(s) and nucleating charge.

[0021] According to certain embodiments, the nucleating charge represents from 0.5% to 1.5% by weight, and preferably from 0.8% to 1.2% by weight, relative to the total weight of powder based on poly-aryl-ether-ketone(s) and nucleating charge. According to certain embodiments, the powder based on poly-aryl-ether-ketone(s) is essentially composed or composed of poly-aryl-ether-ketone(s).

[0022] In some embodiments, the poly-aryl ether ketone is a polyether ketone ketone.

[0023] According to certain embodiments, the poly-aryl-ether-ketone is a polyetherketoneketone essentially consisting of, and preferentially consisting of: a terephthalic repeating unit and, where appropriate, an isophthalic repeating unit, the terephthalic repeating unit (“T unit”) having the formula: the mass proportion of T patterns relative to the sum of the T and I patterns can vary from 0% to 85%. For use of the powder mixture in a method for constructing layer-by-layer objects by sintering caused by electromagnetic radiation, the mass proportion of T patterns relative to the sum of the T and I patterns is preferably from 0% to 25% or from 45% to 75%, more preferably from 0% to 15% or from 55% to 65%, and in particular approximately 0% or approximately 60%.

[0024] According to certain embodiments, in particular when the mixture of powders according to the invention is used in a method of constructing layer-by-layer objects by sintering caused by electromagnetic radiation, the powder based on poly-aryl-ether-ketone(s) advantageously has a particle size distribution, weighted by volume, measured by laser diffraction, according to the ISO 13320: 2009 standard, such that the median diameter D50 has a value of 40 pm to 80 pm.

[0025] According to certain embodiments, the nucleating charge is a talc. The volume-weighted particle size, measured by laser diffraction, according to ISO 13320:2009, such that the median diameter d50 may in particular be such that dso 10 pm, and preferably such that dso < 5 pm. According to particular embodiments, the median diameter d50 is such that dso < 2 pm.

[0026] Advantageously, the Dso / dso ratio is between 10 and 500, preferably between 25 and 250, and more preferably between 40 and 150.

[0027] According to certain embodiments, the nucleating charge is a carbon material. The carbon material may in particular be chosen from the list consisting of carbon black, carbon nanotubes, graphene, or their mixture. The carbon material advantageously has a BET specific surface area greater than or equal to 300 g / m 2 , preferably greater than or equal to 400 g / m 2 , and more preferably greater than or equal to 500 g / m 2 .

[0028] According to certain embodiments, in particular when the mixture of powders according to the invention is used in a method for constructing layer-by-layer objects by sintering caused by electromagnetic radiation, the viscosity of the poly-aryl-ether-ketone(s) is chosen in the range from 400 Pa.s to 1000 Pa.s, as measured at 380°C and at 1 Hz in plane / plane geometry. The present invention also relates to a use of the mixture according to the invention in a method for constructing layer-by-layer objects by sintering caused by electromagnetic radiation(s). Other possible uses are also described.

[0029] The present invention also relates to an object manufactured from a process using a mixture of powders according to the invention. The object has spherulites having a maximum spherulite size at least 2 times smaller than that of an object obtained from the same process but using only the powder based on poly-aryl-ether-ketone(s) present in said mixture of powders.

[0030] Finally, the present invention also relates to an object manufactured from a process using a mixture of powders according to the invention. The object has an elongation at break greater than at least 5% and / or a breaking stress greater than at least 5%, compared to that(s) of an object obtained from the same process but using only the powder based on poly-aryl-ether-ketone(s) present in said mixture of powders.

[0031] Detailed description of the invention

[0032] [Fig.1] shows a diagram of a laser sintering installation

[0033] [Fig. 2] schematically represents the thermal profile, temperature as a function of time, observed by the powder composition according to the invention during a laser sintering process.

[0034] [Fig. 3] represents a snapshot of an optical microscope observation of a microtome section of thickness 3 pm for composition #1 c.

[0035] Definitions

[0036] "Powder" means a fractionated state of matter, generally in the form of very small particles, generally of the order of a hundred micrometers or less. "Powdery" means a state of matter, in particular a state of a composition, which is as a whole in the form of a powder.

[0037] The particle size distribution of a powder can be measured by laser diffraction according to ISO 13320:2009. The particle size distribution of polyaryl ether ketone(s) powder can, for example, be measured on a Malvern Insitec® diffractometer. The rules for representing particle size distribution results are given in ISO 9276-parts 1 to 6. "D50" means the value of the particle diameter of polyaryl ether ketone(s) powder such that the cumulative particle diameter distribution function, weighted by volume, is equal to 50%. Similarly, the terms "D10" and "D90" respectively mean the corresponding diameters so that the cumulative function of the diameters of the particles of powder based on poly-aryl-ether-ketone(s), weighted by the volume, is equal to 10%, and respectively, to 90%.The term "d50" means the value of the diameter of the nucleating charge particles in powder form so that the cumulative volume-weighted particle diameter distribution function is equal to 50%. Similarly, the terms "d10" and "d90" mean the corresponding diameters, respectively, so that the cumulative volume-weighted particle diameter distribution function is equal to 10% and, respectively, to 90%.

[0038] The term "homopolymer" means a polymer consisting of a single repeating unit.

[0039] The term "copolymer" refers to a polymer resulting from the copolymerization of at least two types of chemically different monomers, called comonomers. A copolymer is therefore formed from at least two repeating units derived from different monomers. It can also be formed from three or more repeating units derived from different monomers.

[0040] The copolymer may have a homogeneous structure, in particular of the statistical, alternating or random type, or a heterogeneous structure, in particular of the block type.

[0041] "Consisting essentially of unit(s)" means that the unit(s) represent(s) a molar proportion of 95% to 99.9% relative to the total number of moles of repeating units in the polymer. "Consisting of unit(s)" means that the unit(s) represent(s) a molar proportion of at least 99.9%, in particular 100%, in the polymer relative to the total number of moles of repeating units in the polymer.

[0042] The term "glass transition temperature" means the temperature at which an at least partially amorphous polymer changes from a rubbery state to a glassy state, or vice versa, as measured by differential scanning calorimetry (DSC) according to standard NF EN ISO 11 357-2:2020 in the second heating, using a heating rate of 20°C / min.

[0043] The term “crystallinity rate” means the crystallinity rate as calculated from wide angle X-ray scattering (WAXS) measurements, on a Nano-inXider® type device with the following conditions:

[0044] Wavelength: main Ka1 line of copper (1.54 Angstrom).

[0045] Generator power: 50 kV - 0.6 mA.

[0046] Observation mode: transmission.

[0047] Counting time: 10 minutes.

[0048] Temperature: 25°C

[0049] A spectrum of the scattered intensity is thus obtained as a function of the diffraction angle. This spectrum makes it possible to identify the presence of crystals, when peaks are visible on the spectrum in addition to the amorphous halo. In the spectrum, the area of ​​the crystalline peaks (denoted A) and the area of ​​the amorphous halo (denoted AH) can be measured. The proportion (by mass) in the crystalline phase is estimated by the ratio (A) / (A+AH). The crystallinity rates in the present invention are expressed as the mass proportion of crystalline poly-aryl-ether-ketone(s), relative to the total weight of poly-aryl-ether-ketone(s).

[0050] The term "spherulite" or "spherolite" means an aggregated formation of needle-like crystals with a radiating structure, called fibroradiated. Certain polymers, including poly-aryl-ether-ketones, exhibit this type of crystal organization when they crystallize. The spherulites in the present invention can be observed under an optical microscope on microtome sections. The size of a spherulite corresponds to the diameter of the smallest circle capable of encompassing a spherulite thus observed. It is expressed in micrometers. The maximum size of the spherulites corresponds to the maximum size observed on 3 microtome sections of the same sample, each section generally comprising around thirty spherulites. Thus, the maximum size of the spherulites corresponds to the maximum size observed on a distribution of around 90 spherulites.

[0051] The term "viscosity" means the viscosity as measured at 380°C and 1 Hz under an inert atmosphere (N2), using a TA Instruments ARES G2® oscillatory rheometer, in plane / plane geometry.

[0052] Tensile mechanical properties can be determined on Type 1 BA specimens according to ISO 527-1:2019, at 23°C, with a crosshead speed of 1 mm / min, using for example an MTS 810® device, marketed by MTS Systems Corporation, equipped with a mechanical extensometer. A Type 1 BA specimen can be obtained directly by the manufacturing process for which the said powder is suitable or, if necessary, machined from a solid object if the specimen cannot be obtained directly by this process. For example, Type 1 BA specimens can be manufactured directly by a layer-by-layer object construction process by sintering induced by electromagnetic radiation(s) (no machining is then necessary since this process allows direct manufacture of the specimen).

[0053] According to ISO 527-1:2019, "strain", s, means an increase in length per unit of initial length of the reference length. It is expressed as a dimensionless ratio or as a percentage (%). In particular, "strain at break" means: i) for a brittle material, the strain at the last point recorded before the stress is reduced to a value less than or equal to 10% of the strength when failure occurs before the yield point (which is strictly speaking the "strain at break" according to ISO 527-1:2019), or ii) for a ductile material, the strain at the last point recorded before the stress is reduced to a value less than or equal to 10% of the strength when failure occurs after the yield point (which corresponds to the "nominal strain at break" according to ISO 527-1:2019).

[0054] According to ISO 527-1:2019, "stress" means the force per unit area of ​​the initial cross-sectional area of ​​the test piece's gauge length. It is expressed in megapascals (MPa). "Breaking stress" means the stress at which the test piece breaks.

[0055] The term "specific surface area" refers to the ratio of the actual surface area of ​​a powder to the amount of material in that powder. It is expressed in m 2 / g. It can be measured by adsorption of nitrogen gas on the powder and determined using the Brunauer-Emmett-Tellery (BET) equation. according to ISO 9277:2022.

[0056] The singular forms "a" and "the" applied to the composition constituents, such as the poly-aryl-ether-ketone or the flexible thermoplastic polymer, or to a property of these constituents, mean by default "at least one" and respectively "said at least one". The singular forms nevertheless include, without it being necessary to recall it each time, the embodiments where "a" means "a single one" and "the" means "the only one".

[0057] The word "poly-aryl-ether-ketone(s)", or its acronym "PAEK(s)", should be interpreted as meaning one or more poly-aryl-ether-ketones.

[0058] In all value ranges stated in this application, the terminals are included unless otherwise stated.

[0059] PAEK(s) based powder

[0060] A poly-aryl-ether-ketone (PAEK) has the following formula units: (-Ar-X-) and (-An-Y-), in which:

[0061] - Ar and An each denote a divalent aromatic radical;

[0062] - Ar and An may preferably be chosen from 1,3-phenylene, 1,4-phenylene, 1,1'-biphenylene divalent in positions 3,3', 1,1'-biphenyl divalent in positions 3,4', 1,4-naphthylene, 1,5-naphthylene and 2,6-naphthylene;

[0063] - X denotes an electron-withdrawing group; it may preferably be chosen from the carbonyl group and the sulfonyl group;

[0064] - Y denotes a group selected from an oxygen atom, a sulfur atom, an alkylene group, such as -(CH)2- and isopropylidene.

[0065] In these X and Y units, 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.

[0066] According to a preferred embodiment, 100% of the X groups denote a carbonyl group and 100% of the Y groups represent an oxygen atom.

[0067] Advantageously, the PAEK(s) can be chosen from:

[0068] - a polyether-ketone-ketone, also called PEKK; a PEKK comprises one or more units of formula: -Ph-O-Ph-C(O)-Ph-C(O)-;

[0069] - a polyether-ether-ketone, also called PEEK; a PEEK comprises one or more units of formula: -Ph-O-Ph-O-Ph-C(O)-;

[0070] - a polyether ketone, also called PEK; a PEK comprises one or more units of formula: -Ph-O-Ph-C(O)-;

[0071] - a polyether-ether-ketone-ketone, also called PEEKK; a PEEKK comprises one or more units of formula: -Ph-O-Ph-O-Ph-C(O)- Ph-C(O)-;

[0072] - a polyether-ether-ether-ketone, also called PEEEK; a PEEEK comprises one or more units of formula: -Ph-O-Ph-O-Ph-O- Ph-C(O)-;

[0073] - a poly-ether-diphenyl-ether-ketone also called PEDEK; a PEDEK comprises one or more units of formula: a PEDEK comprises one or more units of formula -Ph-O-Ph-Ph-O-Ph-C(O)-;

[0074] - their mixtures; and,

[0075] - copolymers comprising at least two of the aforementioned units, in which: Ph represents a phenylene group and -C(O)- a carbonyl group, each of the phenylenes being able independently to be of the ortho (1-2), meta (1-3) or para (1-4) type, preferentially being of the meta or para type.

[0076] Additionally, defects, end groups and / or monomers may be incorporated in very small amounts into the polymers as described in the list above without affecting their performance.

[0077] Preferably, in the embodiments where the poly-aryl-ether-ketone is a copolymer, the latter has a homogeneous structure, in particular of the statistical type.

[0078] According to certain embodiments, the PAEK is a polyetherketoneketone essentially consisting of, and preferentially consisting of: a terephthalic repeating unit and, where appropriate, an isophthalic repeating unit, the terephthalic repeating unit (“T unit”) having the formula: the isophthalic unit (“I unit”) having the formula:

[0079] The mass proportion of T units relative to the sum of T and I units can vary from 0% to 85%. The mass proportion of T units relative to the sum of T and I units can in particular be from 0% to 5%; or from 5% to 10%; or from

[0080] 10% to 15%; or 15% to 20%; or 15% to 20%; or 20% to 25%; or

[0081] 25% to 30%; or 30% to 35%; or 35% to 40%; or 40% to 45%; or

[0082] 45% to 50%; or from 50% to 55%; or from 55% to 60%; or from 60% to 65%; or from

[0083] 65% to 70%, or 70% to 75%, or 75% to 80%, or 80% to 85%. The choice of the molar proportion of T units relative to the sum of T and I units is one of the factors that allows the crystallization rate properties of polyether-ketone-ketones to be adjusted. A given molar proportion of T units relative to the sum of T and I units can be obtained by adjusting the respective concentrations of the reactants during polymerization, in a manner known per se.

[0084] For use of the powder in a method for constructing layer-by-layer objects by sintering caused by electromagnetic radiation, the mass proportion of T units relative to the sum of the T and I units is preferably from 0% to 25% or from 45% to 75%, and more preferably from 0% to 15% or from 55% to 65%. The mass proportion of T units relative to the sum of the T and I units may in particular be approximately 0% or approximately 60%.

[0085] Such poly-aryl-ether-ketones are commercially available under the name Kepstan® from Arkema. In some embodiments, PAEK may be a homopolymer consisting essentially of, or even consisting of, a repeating unit having the formula:

[0086] Such poly-aryl ether ketones are commercially available under the name KetaSpire® from Solvay, under the name VestaKeep® from Evonik and PEEK Victrex® from Victrex.

[0087] According to certain embodiments, the PAEK may be a copolymer essentially consisting of, or even consisting of, a repeating unit having the formula (III) and a repeating unit having the formula:

[0088] The molar proportion of unit (III) relative to the sum of units (III) and (IV) can range from 0% to 99%, preferably from 0% to 95%.

[0089] According to certain embodiments, the PAEK may be a copolymer essentially consisting of, or even consisting of, a repeating unit having the formula (III) and a repeating unit having the formula:

[0090] The molar proportion of unit (III) relative to the sum of units (III) and (V) can range from 0% to 99%, preferably from 0% to 95%.

[0091] The glass transition temperature of PAEK is preferably between 100 and 250°C, preferably between 120 and 200°C, and most preferably between 140 and 180°C.

[0092] Advantageously, the PAEK has a viscosity, measured at 380°C and 1 Hz, greater than 100 Pa s, preferably greater than 200 Pa s and more preferably greater than 300 Pa s. The viscosity of the PAEK is generally not greater than 1500 Pa.s. The viscosity of the PAEK may in particular be from 300 Pa s to 600 Pa s, or from 600 Pa s to 800 Pa s, or from 800 Pa s to 1000 Pa s, or from 1000 Pa s to 1200 Pa s, or from 1200 Pa s to 1500 Pa s.

[0093] According to certain embodiments, in particular for powder mixtures intended to be used in a sintering process, the viscosity of the PAEK(s), measured at 380°C and 1 Hz, is chosen in the range from 400 Pa.s to 1000 Pa.s.

[0094] According to certain embodiments, the PAEK-based powder comprises at least two PAEKs. The powder may in particular comprise at least 50% by weight of a PEKK, relative to the total weight of PAEKs, and at least one other PAEK different from said PEKK.

[0095] According to some embodiments, the at least two PAEKs may be PAEKs having different repeating units. For example, a PEKK and a PEEK may be cited.

[0096] According to certain embodiments, these at least two PAEKs may be copolymers having the same repeating units but with a different ratio. For example, two PEKKs having a different proportion of T:l units may be cited.

[0097] According to certain embodiments, the powder comprises a single PAEK. According to certain embodiments, this PAEK may be a PEKK. For use of the PEKK-based powder in a method for constructing layer-by-layer objects by sintering caused by electromagnetic radiation, the mass proportion of T units relative to the sum of the T and I units is preferably from 0% to 25% or from 45% to 75%, and more preferably from 0% to 15% or from 55% to 65%. The mass proportion of T units relative to the sum of the T and I units may in particular be approximately 0% or approximately 60%.

[0098] The PAEK(s)-based powder comprises at least 60% by weight of PAEK(s), relative to the total weight of said powder. The powder may comprise at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 98%, or at least 99%, or at least 99.5% by weight of PAEK(s), relative to the total weight of said powder.

[0099] The PAEK(s)-based powder may comprise, in addition to the PAEK or PAEKs, another thermoplastic polymer than the PAEK(s) and / or additives.

[0100] The PAEK(s)-based powder may comprise from 0% to 40% by weight of another thermoplastic polymer, relative to the weight of said powder. As another thermoplastic polymer, mention may be made of a poly(etherimide). A poly(etherimide) is known to be an amorphous polymer miscible with PAEK(s). It may be used to adjust the crystallization kinetics and / or crystallization of the composition of the powder mixture according to the invention. According to certain embodiments, the PAEK(s)-based powder may comprise from 5% to 30% by weight of another thermoplastic polymer than the PAEK(s), in particular a polyetherimide.

[0101] The PAEK(s)-based powder may also comprise one or more additives. The additives generally represent less than 5% by weight relative to the total weight of the powder mixture. Preferably, the additives represent less than 1% by weight relative to the total weight of the powder mixture. Among the additives, mention may be made of flow agents, stabilizers (light, in particular UV, thermal), optical brighteners, dyes, pigments and energy-absorbing additives (including UV absorbers).

[0102] In some embodiments, the PAEK(s)-based powder does not include a flow agent. The PAEK(s)-based powder notably does not include hydrophilic silica.

[0103] According to certain embodiments, the PAEK(s)-based powder may comprise a phosphate as a thermal stabilizer. The phosphate may in particular be a phosphate salt, such as a salt of H2PO4; HPO4 2 ; PO43 ; or a mixture thereof, preferably having a sodium ion, a potassium ion or a calcium ion, and more preferably a sodium ion, as a counterion. Advantageously, the phosphate is incorporated into the PAEK(s)-based powder in a proportion greater than or equal to 500 ppm, or greater than or equal to 750 ppm, or greater than or equal to 1000 ppm, or greater than or equal to 1500 ppm, or greater than or equal to 2000 ppm, or greater than or equal to 2500 ppm, relative to the total weight of PAEK. According to certain embodiments, the PAEK(s)-based powder may consist of at least 60% by weight of PAEK(s), from 0% to 40% by weight of another thermoplastic polymer and from 0% to 5% by weight of an additive, relative to the total weight of said powder.

[0104] According to certain embodiments, the PAEK(s)-based powder may consist of at least 95% by weight of PAEK(s) and from 0% to 5% by weight of an additive, relative to the total weight of said powder.

[0105] In some embodiments, the PAEK(s)-based powder may consist essentially of PAEK(s).

[0106] The poly-aryl-ether-ketone(s)-based powder advantageously has a particle size distribution, as measured by laser diffraction according to ISO 13320:2009, with a median diameter Dso such that: D50 < 300 pm, According to certain embodiments, D50 < 200 pm, or D50 < 150 pm, or D50 < 120 pm, or D50 < 100 pm, or D50 < 80 pm.

[0107] According to certain embodiments, in particular for powder mixtures intended to be used in a sintering process, D50 is advantageously such that: 40 pm < D50 < 80 pm. In these embodiments, the particle size distribution is preferably such that D10 > 15 pm, 40 pm < D50 < 80 pm and D90 < 240 pm. In particular, it is possible to have D90 < 220 pm or even d90 < 200 pm.

[0108] Nucleating charge

[0109] The nucleating filler is in powder form. It is chosen from a silicate, a carbon material, or their mixture. A proportion of 0.1% to 2% by weight of nucleating filler relative to the total weight of poly-aryl-ether-ketone powder and nucleating filler has proven to be optimal for enabling the reduction of the size of spherulites during the construction of objects by making it possible to improve certain mechanical properties (elongation at break / breaking stress), without modifying other properties targeted for the application (including the crystallinity rate).

[0110] Preferably, the nucleating charge represents from 0.5% to 1.5% by weight, relative to the total weight of powder based on poly-aryl-ether-ketone and nucleating charge. Preferably again, the nucleating charge represents from 0.8% to 1.2% by weight, relative to the total weight of powder based on poly-aryl-ether-ketone and nucleating charge.

[0111] A silicate is a mineral containing in its structure one or more anions of chemical formula: SiO4-x (4 ' 2X)_ , where 0 < x < 2. The counterion(s) may, among other things, be predominantly aluminum, potassium, magnesium, sodium, calcium, iron, or a mixture of these elements. The silicate may be present in hydroxylated form.

[0112] The nucleating charge can in particular be chosen from: talc, mica, kaolin, or their mixture.

[0113] According to particular embodiments, the nucleating charge is a talc.

[0114] The nucleating charge, particularly when it is a silicate, advantageously has a particle size distribution such that dso 10 pm, and preferably such that dso < 5 pm.

[0115] According to certain preferred embodiments, there is dso 2 pm.

[0116] Furthermore, according to certain embodiments, the Dso / dso ratio ranges from 10 to 500, preferably from 25 to 250, and more preferably from 40 to 150.

[0117] In embodiments where the nucleating charge is a carbon material, it may in particular be chosen from carbon black, graphene, carbon nanotubes, or a mixture thereof.

[0118] The BET specific surface area of ​​the nucleating charge being a carbon material is greater than or equal to 200 g / m 2 It can advantageously be greater than or equal to 300 g / m 2 , or greater than or equal to 400 g / m 2 , or greater than or equal to 500 g / m 2 , or greater than or equal to 600 g / m 2 , or greater than or equal to 700 g / m 2 , or greater than or equal to 800 g / m 2 , or greater than or equal to 900 g / m 2 , or greater than or equal to 1000 g / m 2 .

[0119] Preferably the BET specific surface area of ​​the nucleating charge being a carbon material is greater than or equal to 400 g / m 2 , and more preferably is greater than or equal to 500 g / m 2 . Dry mix of powders

[0120] The dry-blending process consists of mixing the poly-aryl-ether-ketone(s)-based powder and the nucleating charge in their solid form, dry. It allows a dry blend of powders to be obtained. The mixing speed and / or the mixing time are chosen by the person skilled in the art to obtain a homogeneous mixture in a manner known per se.

[0121] A dry mixing process includes at least the following steps:

[0122] (i) supply of the powder based on poly-aryl-ether-ketone(s),

[0123] (ii) providing the nucleating charge in powder form, and

[0124] (iii) at least one step of dry mixing at least a portion of said poly-aryl-ether-ketone(s)-based powder with at least a portion of said nucleating charge in powder form.

[0125] In a preferred embodiment, the dry mixing process is carried out by means of a single step of mixing the poly-aryl-ether-ketone(s)-based powder with the nucleating charge in powder form, in the desired final proportions of the powder mixture according to the invention.

[0126] According to other embodiments, the dry mixing method is implemented by means of several steps of mixing the powder based on poly-aryl-ether-ketone(s) with the nucleating charge in powder form. In particular, a powder mixture where the nucleating charge is in a greater proportion than in the final powder mixture can initially be prepared (master batch). This master batch can then be mixed in one or more times with powder based on poly-aryl-ether-ketone(s) in order to obtain the desired proportion of nucleating charge.

[0127] According to preferred embodiments, the dry mixture of powders according to the invention is essentially constituted, or constituted of said powder based on polyaryletherketone(s) and said nucleating charge in powder form.

[0128] Uses

[0129] The powders according to the invention can be used in several manufacturing processes, including the manufacturing processes listed in a non-exhaustive manner below. The processes for constructing layer-by-layer objects by sintering caused by electromagnetic radiation(s), in particular by infrared radiation and laser radiation, are well known to those skilled in the art. With reference to Figure 1, the laser sintering device 1 comprises a sintering enclosure 10 in which are arranged a feed tank 40 containing the powder composition (dry mixture of powders according to the invention) to be sintered, a horizontal plate 30 for supporting the three-dimensional object 80 under construction and a laser 20. The powder composition is taken from the feed tank 40 and deposited on the horizontal plate 30, forming a thin layer 50 of powder composition constituting the three-dimensional object 80 under construction.A compactor / scraper roller (not shown) ensures good uniformity of the layer 50 of powder composition. The layer 50 of powder composition, under construction, is heated using infrared radiation 100 to reach a substantially uniform temperature equal to a predetermined construction temperature Te. In traditional construction processes for sintering PAEK(s)-based powders, Te is generally approximately 20°C lower than the melting temperature of the powder, as measured by DSC in the first heating with a temperature ramp equal to 20°C / min. In certain cases Te may even be lower. The energy required to sinter the PAEK(s)-based powder particles at different points of the layer 50 of powder composition is then provided by laser radiation 200 from the laser 20 mobile in the (xy) plane, according to a geometry corresponding to that of the object.The molten powder incorporates the nucleating charge, then re-solidifies forming a sintered portion 55 while the remainder of the layer 50 of powder composition remains in the form of unsintered powder composition 56. Several passes of laser radiation 200 may be necessary in certain cases. Then, the horizontal plate 30 is lowered along the (z) axis by a distance corresponding to the thickness of a layer of powder composition, and a new layer is deposited. The laser 20 provides the energy necessary to sinter the PAEK(s)-based 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 finished, it is removed from the horizontal plate 30 and the unsintered powder composition 56 can be sieved before being returned, if necessary, to the feed bin 40 to serve as recycled powder.

[0130] The dry powder mixtures according to the invention can also be used in surface coating processes, particularly for metal surfaces. Different processes can be used to obtain a coating on a metal part. One example is dipping in a fluidized bed, in which the metal part is heated and then dipped into the fluidized powder bed. It is also possible to carry out so-called electrostatic powdering (electrically charged powder powdered onto a grounded metal part), in which case a post-heat treatment is carried out to achieve the coating. An alternative is to carry out the powdering on a previously heated part, which eliminates the heat treatment after powdering. Finally, it is possible to carry out flame powdering, in which case the powder is sprayed molten onto a possibly preheated metal part.

[0131] The dry powder mixes 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, then compacted and finally melted to produce the part. Finally, suitable cooling, often quite slow, is carried out in order to limit the presence of internal stresses in the part.

[0132] Finally, the dry powder mixtures according to the invention can also be used for impregnating fibers with a resin powder for the manufacture of semi-finished products, the powder being able to be used in a fluidized bed or dispersed in an aqueous solution.

[0133] Characterization of manufactured objects

[0134] The objects manufactured from one of the aforementioned manufacturing processes, for example a process for constructing layer-by-layer objects by sintering caused by electromagnetic radiation(s), using the powder mixture according to the invention (additive composition) have at least one, and according to certain embodiments all, of the following properties: a maximum spherulite size at least 2 times smaller than that of an object obtained according to the same process using a non-additive composition (powder based on PAEK(s) only); a crystallinity rate comparable to that of an object obtained according to the same process using a non-additive composition (powder based on PAEK(s) only); an elongation at break greater by at least 5%, compared to that of an object obtained according to the same process using a non-additive composition (powder based on PAEK(s) only);a breaking stress at least 5% higher than that of an object obtained by the same process using a non-additive composition (powder based on PAEK(s) only);

[0135] Objects manufactured by a process for building objects layer-by-layer by sintering induced by electromagnetic radiation(s) from a mixture of powders in which the poly-aryl-ether-ketone is a PEKK, in particular a copolymer essentially consisting of or consisting of isophthalic and terephthalic repeating units, and preferably having a T:I ratio of 55:45 to 65:35, advantageously have the following properties: a degree of crystallinity greater than or equal to 10%, or greater than or equal to 12%, or greater than or equal to 14%, as measured by wide angle X-ray scattering (WAXS); an elongation at break of at least 2.5% and / or a breaking stress of at least 90 MPa, as measured on Type 1 BA specimens according to ISO 527-1:2019, at 23°C, with a crosshead speed of 1 mm / min. a maximum spherulite size of less than 10 pm.

[0136] Examples

[0137] Raw materials:

[0138] Polyetherketoneketone with a T / l ratio of 60 / 40: KEPSTAN®, grade PEKK 6000, marketed by Arkema. The polyetherketoneketone used has a viscosity of 820 Pa.s, at 380°C and at 1 Hz in plane-plane geometry. The polyetherketoneketone used is in the form of a powder with a particle size distribution such that D10 = 23 microns, Dso = 53 microns and D90 = 113 microns, the latter being suitable for a laser sintering process.

[0139] Talc 1: Jetfine® 1A talc, marketed by Imerys. This talc has a particle size distribution such that dso= 3.5 pm and d95= 7 pm;

[0140] Talc 2: Talc Jetfine® 07, marketed by Imerys. This talc has a particle size distribution such that dso= 2.5 pm and d95= 5.2 pm;

[0141] Talc 3: Talc Nano-ace® D1000, marketed by Nippon Talc. This talc has a particle size distribution such that dso = 1.0 pm.

[0142] Talc 4: Talc SG2000®, marketed by Nippon Talc. This talc has a particle size distribution such that dso = 0.85 pm.

[0143] Talc 5: Talc Nano-ace® D600, marketed by Nippon Talc. This talc has a particle size distribution such that d50 = 0.60 pm.

[0144] NC: Ketjenblack® EC-600JD carbon black marketed by Nouryon. This carbon black has aggregates of approximately 0.1 pm to 1 pm in size. It also has a BET of 1400 m 2 / g.

[0145] Silica 1: Hydrophilic fumed silica Aerosil® R150, marketed by Evonik. This silica has aggregates of size around 0.1 μm. It has a BET of 135-165 μm 2 / g.

[0146] Dry-blends of polyetherketoneketone powder and a nucleating filler were prepared using a Magimix mixer, with a mixing time of 100 s.

[0147] The composition of the different mixtures (#2 - #10, #11 c) is presented in

[0148] Table 1.

[0149] Table 1

[0150] Composition #1 c corresponds to the non-additive powder, composed only of polyetherketoneketone.

[0151] Estimation of the size of the spherulites:

[0152] A simulation of a laser irradiation powder sintering process was implemented by placing each mixture in an ARES G2 rheometer, marketed by TA Instrument. More precisely, the compositions were heated to 380°C to melt the PEKK (simulating laser heating), then rapidly cooled to 285°C (simulating re-solidification), and finally cooled at a ramp of 0.5°C / min to a temperature of 165°C (simulating slow cooling to bath temperature) (see temperature profile versus time in Figure 2).

[0153] The objects resulting from the simulation of a sintering process were observed under an optical microscope on microtome sections of 3 μm thickness. The maximum size of the spherulites was measured. The crystallinity of these objects was also measured, by WAXS.

[0154] The results are presented in Table 2

[0155] Table 2

[0156] Figure 3 represents the optical microscope view of a microtome section of the object resulting from the simulation of the sintering process with composition #1 c. The maximum spherulite size is 20 pm (circle encompassing this spherulite shown).

[0157] ISO 527 / 1 BA specimens are printed in the xy plane using a P810® printer, marketed by EOS. The construction temperature is set at 285°C and the laser energy at 29 mJ / mm 2The breaking stress for a non-additive PEKK powder (composition #1 c) is 85 MPa and the elongation at break is 2.3%.

[0158] In comparison, the breaking stress of a mixture of PEKK powder and 1% by weight of talc (especially composition #6) is greater than 90 MPa. Its elongation at break is greater than 2.5%.

Claims

Claims 1. Dry mixture of powders comprising: a powder based on poly-aryl-ether-ketone(s) having a volume-weighted particle size distribution, measured by laser diffraction, according to ISO 13320: 2009, such that the median diameter D50 is such that D50 < 300 pm, and a nucleating filler in powder form, the nucleating filler being chosen from a silicate, a carbonaceous material having a BET specific surface area greater than or equal to 200 g / m 2 , or their mixture, the nucleating charge representing from 0.1% to 2% by weight, relative to the total weight of powder based on poly-aryl-ether-ketone(s) and nucleating charge.

2. Mixture of powders according to claim 1, in which said nucleating charge represents from 0.5% to 1.5% by weight, and preferably from 0.8% to 1.2% by weight, relative to the total weight of powder based on poly-aryl-ether-ketone(s) and nucleating charge.

3. A powder mixture according to any one of claims 1 and 2, wherein the poly-aryl-ether-ketone(s)-based powder is essentially made up of or consisting of poly-aryl-ether-ketone(s).

4. A powder mixture according to any one of claims 1 to 3, wherein the poly-aryl-ether-ketone is a polyetherketoneketone.

5. A powder mixture according to any one of claims 1 to 4, wherein the poly-aryl-ether-ketone(s)-based powder has a volume-weighted particle size distribution, measured by laser diffraction, according to ISO 13320:2009, such that the median diameter D50 has a value of 40 pm to 80 pm.

6. A powder mixture according to any one of claims 1 to 5, wherein the nucleating filler is a talc.

7. A powder mixture according to any preceding claim, wherein the nucleating charge has a volume-weighted particle size distribution, measured by laser diffraction, according to ISO 13320:2009, such that the median diameter d50 is such that dso 10 pm, and preferably such that dso < 5 pm.

8. A powder mixture according to any preceding claim, wherein the nucleating agent has a volume-weighted particle size distribution, measured by laser diffraction, according to ISO 13320:2009, such that the median diameter d50 is such that dso < 2 pm.

9. Mixture of powders according to any one of claims 7 and 8, in which the Dso / dso ratio is between 10 and 500, preferably between 25 and 250, and more preferably between 40 and 150.

10. A powder mixture according to any one of the preceding claims, wherein the nucleating charge is a carbonaceous material having a BET specific surface area greater than or equal to 300 g / m 2 , preferably still greater than or equal to 400 g / m 2 , and more preferably greater than or equal to 500 g / m 2 .

11. A powder mixture according to any preceding claim, wherein the nucleating agent is a carbon material selected from the list consisting of carbon black, carbon nanotubes, graphene, or a mixture thereof.

12. A powder mixture according to any preceding claim, wherein the viscosity of the polyaryl ether ketone(s) in the polyaryl ether ketone-based powder is selected from the range 400 Pa.s to 1000 Pa.s, as measured at 380°C and 1 Hz in plane / plane geometry.

13. Use of a mixture of powders according to any one of claims 1 to 12, in a process for constructing layer-by-layer objects by sintering caused by electromagnetic radiation(s).

14. Object manufactured from a process using a mixture of powders according to any one of claims 1 to 12, said object having a maximum size of spherulites at least 2 times smaller than that of an object obtained from the same process but using only the powder based on poly-aryl-ether-ketone(s) present in said mixture of powders.

15. An object manufactured from a process using a mixture of powders according to any one of claims 1 to 12, said object having an elongation at break at least 5% higher and / or a breaking stress at break at least 5% higher, compared to that(s) of an object obtained from the same process but using only the powder based on poly-aryl-ether-ketone(s) present in said mixture of powders.

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