Composition of thermoplastic polymer powders for 3D printing

Abstract

The present invention relates to a composition of thermoplastic polymer powders for the manufacture of articles by 3D printing, in particular by sintering, comprising a mixture of thermoplastic polymer powders, one of which is present in a small amount, making it possible to obtain printed parts having an improved mechanical property. The invention also relates to a method for preparing this powder composition as well as its use in a manufacturing method by laser sintering, and the articles manufactured from said powder composition.

Description

Title of the invention: Composition of thermoplastic polymer powders for 3D printing Field of invention

[0001] The present invention relates to a composition of thermoplastic polymer powders for the manufacture of articles by 3D printing, in particular by sintering, comprising a mixture of thermoplastic polymer powders, one of which is present in a small quantity, making it possible to obtain printed parts having an improved mechanical property.

[0002] The invention also relates to a process for preparing this powder composition as well as its use in a laser sintering manufacturing process, and the articles manufactured from said powder composition. Technical background

[0003] Additive manufacturing on thermoplastic polymer powder beds (SLS, MJF, HSS, etc.) makes it possible to build parts with complex geometry, including in series production. It allows the production of a large number of parts simultaneously, with excellent resolution and very good mechanical properties, which gives them an advantage over other additive manufacturing processes such as fused deposition.

[0004] Polyamide powders are particularly interesting for the aforementioned additive manufacturing technology. Examples include commercial powders based on polyamide 12 such as Orgasol® from Arkema, Durafom® from 3D-Systems, Vestosint® from Evonik, or PA2200® from EOS.

[0005] We can also cite commercial powders based on polyamide 11 such as Rilsan® from Arkema.

[0006] Other types of thermoplastic polymers are also available on the market, for example polyetherketoneketone powders such as Kepstan® from Arkema.

[0007] Parts printed from these powders have interesting mechanical properties. But there is a continuous need to improve their mechanical properties, in particular the properties at break such as for example the elongation at break, in order to meet the search for performance with increasingly high requirements over time. It is also known that the properties at break are, in general, lower at the end of an additive manufacturing process compared to more traditional processes, such as injection; which reinforces the need to improve the properties at break for additive manufacturing processes. Summary of the invention

[0008] Thus, the aim of the present invention is to propose a composition of thermoplastic polymer powders containing at least 2 distinct and particularly chosen thermoplastic polymer powders, one powder of which is present in the composition in a small quantity (called "auxiliary powder"), making it possible to obtain sintered objects with better mechanical properties, in particular in terms of elongation at break.

[0009] For the purposes of the present invention, the 2 powders of distinct thermoplastic polymers may be powders of the same thermoplastic polymer or two different thermoplastic polymers. The powders of thermoplastic polymers differ in at least one of their properties. These properties may be their appearance, for example their particle size, or their thermal properties (for example, the degree of crystallinity, the nature of the crystalline phases, the melting temperature, the enthalpy of fusion, etc.) or their rheological properties.

[0010] According to a first aspect, the invention relates to a composition of thermoplastic polymer powders comprising: i. a thermoplastic polymer powder A; ii. 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, relative to the total mass of the composition, of a thermoplastic polymer powder B, the powder B having - a melting temperature (Tf) lower than or equal to, preferably lower than, the Tf of powder A, the Tf being measured according to standard NF EN ISO 11357-3:2018; and / or - a ratio of the volume flow index (MVR) of powder B to the volume flow index (MVR) of powder A greater than 5, preferably greater than 10, even more preferably greater than 20, the MVR being measured according to the ISO 1133 standard.

[0011] According to another aspect, the invention relates to a composition of thermoplastic polymer powders comprising, relative to the total mass of the composition: i. 59.5 to 99.5% by mass of a thermoplastic polymer powder A as defined above; ii. 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, of a thermoplastic polymer powder B as defined above; iii. 0 to 40% by mass, preferably 0.05 to 40% by mass of one or more additives and / or one or more fillers.

[0012] The composition of thermoplastic polymer powders comprises 0.1 to 3% by mass, preferably 0.1 to 2%, 0.1 to 1.8%, 0.1 to 1.5%, 0.5 to 2%, 0.5 to 1.8%, 0.5 to 1.5%, 0.7 to 1.5%, 0.9 to 1.5%, 1 to 1.5% or 0.9 to 1.4% in mass of powder B, relative to the total mass of the composition.

[0013] According to one embodiment, the Tf of powder B is equal to the Tf of powder A and the MVR ratio of powder B to MVR of powder A is greater than 5, preferably greater than 10, even more preferably greater than 20, the MVR being measured according to the ISO 1133 standard,

[0014] The thermoplastic polymer powders that can be used in the context of the present invention can in particular be chosen from polyolefins such as polypropylene and polyethylene (olefinic base waxes would not fall outside the scope of the present invention), polycarbonate, polymethylmethacrylate (PMMA), polyamides and thermoplastic elastomers such as polyether block amides (PEBA), polyesters and polyether blocks (COPE), thermoplastic polyurethanes (TPU) and their mixtures, PAEKs such as PEKK and PEEK-based copolymer, preferably polyamides.

[0015] Thus, according to a particular aspect of the invention, the present invention aims to propose a composition of polyamide powders containing at least 2 distinct and particularly chosen polyamide powders, one powder of which is present in the composition in a small quantity (called "auxiliary powder"), making it possible to obtain sintered objects with better mechanical properties, in particular in terms of elongation at break.

[0016] Preferably, powder A and / or powder B is a polyamide powder, preferably, powder A and powder B are polyamide powders.

[0017] According to one embodiment, powder A is a polyamide 12 or polyamide 11 powder.

[0018] According to one embodiment, powder B is a polyamide 12 or polyamide 11 powder.

[0019] According to one embodiment, when powder A is a polyamide 11 powder, powder B is a polyamide 11 powder or a polyamide 12 powder.

[0020] According to one embodiment, when powder A is a polyamide 12 powder, powder B is a polyamide 12 powder.

[0021] According to one embodiment, powder A has a melting temperature (Tf) less than or equal to 250°C, preferably less than or equal to 210°C.

[0022] According to one embodiment, powder B has a melting temperature (Tf) less than or equal to 210°C, preferably between 80 and 210°C, preferably between 100 and 200°C.

[0023] The volume melt index (MVR) of powder B may typically be greater than 50 cmVIOmin, preferably greater than 100 cmVIOmin, even more preferably greater than 200 cmVIOmin.

[0024] According to one embodiment, powder A has a Dv50 of 20 to 100 pm, preferably of 30 to 80 pm, even more preferably of 40 to 60 pm.

[0025] According to one embodiment, powder B has a Dv50 of 1 to 60 pm, preferably of 3 to 50 pm, even more preferably of 4 to 20 pm.

[0026] The Dv50 of powder B may be greater than, less than or equal to the Dv50 of powder A.

[0027] Preferably, the Dv50 of powder B is lower than the Dv50 of powder A. According to one embodiment, the Dv50 of powder B is 5 to 80% of the Dv50 of powder A, preferably 10 to 60% of the Dv50 of powder A.

[0028] It has been observed in the context of the present invention that the addition of a small amount of a particular auxiliary powder in a thermoplastic polymer powder, in particular in a polyamide powder, suitable for 3D printing by sintering, surprisingly makes it possible to obtain sintered objects with better mechanical properties, in particular in terms of improved elongation at break.

[0029] The present invention also relates to a 3D printing method, preferably an electromagnetic radiation-induced sintering method, using the powder as defined above, or a powder comprising a portion of said non-agglomerated powder and recovered after one or more constructions within the same or a different printing process.

[0030] Preferably, the electromagnetic radiation is chosen from one or more laser beams, infrared radiation or UV radiation.

[0031] The present invention also relates to an article obtained by the 3D printing process as defined above.

[0032] The article can be chosen from prototypes, models and parts, in particular in the automotive, nautical, aeronautical, aerospace, medical (prostheses, hearing systems, cellular tissues, etc.) fields, textiles, clothing, fashion, decoration, design, cases for electronics, telephony, IT, lighting, sport, industrial tools.

[0033] According to yet another aspect, the invention relates to the use of 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, relative to the total mass of the composition, of a thermoplastic polymer powder B, in a composition containing a thermoplastic polymer powder A, in a 3D printing process, preferably by sintering, the powder B having - a melting temperature (Tf) less than or equal to, preferably less than, the Tf of the powder A, the Tf being measured according to standard NF EN ISO 11357-3:2018; and / or - a volume flow index (MVR) ratio of powder B to volume flow index (MVR) of powder A being greater than 5, preferably greater than 10, even more preferably greater than 20, the MVR being measured according to the ISO 1133 standard,

[0034] to improve the elongation at break.

[0035] The thermoplastic polymer powders are preferably polyamide powders.

[0036] The invention is now described in detail and in a non-limiting manner in the following description. Description of the invention Definition

[0037] In the present description of the invention, including in the examples below.

[0038] The term "powder" is understood to denote a solid material in finely divided form, generally in the form of very small particles, generally of the order of a few hundred micrometers or less.

[0039] The Dv50 also called here “volume median diameter” corresponds to the value of the particle size which divides the population of particles examined exactly in two, as measured by laser diffraction according to the ISO 13320: 2009 standard, for example on a Malvern diffractometer of the Insitec® type.

[0040] The term "melting temperature (Tf)" is understood to mean the temperature at which an at least partially crystalline compound passes into the viscous liquid state as measured according to standard NF EN ISO 11357-3:2018. In the present invention, the value was determined during the heating step at a rate of 20 °C / min during the first heating.

[0041] Unless otherwise indicated, this is more particularly the peak melting temperature as defined below.

[0042] More specifically, the following terms are understood to mean in relation to the melting temperature: • a “peak” means the portion of the differential scanning calorimetry (DSC) thermogram that deviates from the specimen baseline to reach a maximum or minimum and then returns to the specimen baseline. Such a peak may indicate a first-order transition; • a “baseline” means the part of the recorded thermogram without any transition, in particular here without any first-order transition of the melting type. At a transition zone, a virtual baseline can be determined: it is an imaginary line drawn through the transition zone, assuming that the heat due to the transition is zero. The virtual baseline can be drawn by interpolating the baseline of the specimen at by means of a straight line; • a “melting peak temperature” means the temperature at which the distance is greatest between the thermogram and the virtual baseline during a peak.

[0043] The melt flow rate (MVR) is measured by a Zwick MFlow measuring device, manufactured by Zwick according to ISO 1133.

[0044] The elongation at break is measured according to the ISO 527-1:2019 standard.

[0045] In the present description, it is specified that when reference is made to in intervals, expressions of the type "between...and..." or "from...to..." include the limits of the interval.

[0046] Unless otherwise stated, the percentages expressed are mass percentages. Unless otherwise stated, the parameters referred to are measured at atmospheric pressure and room temperature (23°C).

[0047] Composition of thermoplastic polymer powders Thermoplastic polymer powders A and B

[0048] The thermoplastic polymer powders A and B may be commercial powders available on the market.

[0049] We can notably cite commercial powders based on polyamide 12 such as Orgasol® from Arkema, Durafom® from 3D-Systems, Vestosint® from Evonik, or PA2200® from EOS.

[0050] We can also cite commercial powders based on polyamide 11 such as Rilsan® Invent from Arkema.

[0051] We can also cite commercial powders based on PEKK such as Kepstan® from Arkema.

[0052] The thermoplastic polymer powders A and B can be obtained by any type of suitable process known to those skilled in the art.

[0053] Preferably, powder A and / or powder B is a polyamide powder.

[0054] Preferably, powders A and B are polyamide powders, even more preferably potentially, chosen from polyamide 11 and polyamide 12 powders.

[0055] The polyamides within the scope of the present invention may be homopolyamides or copolyamides.

[0056] By homopolyamide in the sense of the invention is meant the polymerization products of aminocarboxylic acid, lactam or diacid monomers with diamines.

[0057] By copolyamide in the sense of the invention, we mean a copolymer resulting from the polymerization of at least two different monomers, called "co-monomers", that is to say at least one monomer and at least one co-monomer (monomer different from the first monomer), being chosen from aminocarboxylic acids, lactams, diamine-diacid couples. The copolyamide may comprise a monomer said to be the majority, that is to say representing at least 80% by mass of the total mass of the mixture of monomers, and at least one co-monomer said to be the minority, representing at most 20% by mass of the total mass of the total mixture of monomer(s) and co-monomer(s).

[0058] The term "monomer" in the following description must be taken in the sense of "repeating unit". The case where a repeating unit is made up of the association of a diacid with a diamine is particular. It is considered that it is the association of a diamine and a diacid, that is to say the diamine.diacid pair (in equimolar quantity), which corresponds to the monomer. This is explained by the fact that individually, the diacid or the diamine is only a structural unit, which is not sufficient on its own to form a polymer.

[0059] As examples of amino acid or aminocarboxylic acid type monomers, mention may be made of those having from 4 to 18 carbon atoms, such as aminocaproic, amino-7-heptanoic, amino-11-undecanoic, n-heptyl-11-aminoundecanoic and amino-12-dodecanoic acids.

[0060] Examples of lactam-type monomers include those having 3 to 18 carbon atoms on the main cycle and which may be substituted. Examples include [3,[3-dimethylpropriolactam, α,α-dimethylpropriolactam, amylolactam, caprolactam also called lactam 6, capryllactam also called lactam 8, oenantholactam, 2-pyrrolidone and lauryllactam also called lactam 12.

[0061] Examples of dicarboxylic acids that may be mentioned are acids having between 4 and 18 carbon atoms. Examples that may be mentioned are adipic acid, sebacic acid, azelaic acid, suberic acid, isophthalic acid, butanedioic acid, 1,4 cyclohexyldicarboxylic acid, terephthalic acid, the sodium or lithium salt of sulphoisophthalic acid, dimerized fatty acids (these dimerized fatty acids have a dimer content of at least 98% and are preferably hydrogenated) and dodecanedioic acid.

[0062] As an example of diamine, mention may be made of aliphatic diamines having from 4 to 18 atoms, which may be aryl and / or saturated cyclic. As examples, mention may be made of hexamethylenediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, 5-dodecamethylenediamine, 1,5-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, diamine polyols, isophoronediamine (IPD), methyl pentamethylenediamine (MPDM), bis(aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), methaxylyenediamine, bis-p-aminocyclohexylmethane and trimethyl-hexamethylenediamine.

[0063] According to one embodiment, powder A is a polyamide powder, which can be A homopolyamide or a copolyamide.

[0064] According to one embodiment, powder B is a polyamide powder, which may be a homopolyamide or a copolyamide.

[0065] According to one embodiment, powder A and / or powder B is chosen from PA 6, PA 11, PA 12, PA 66, PA 610, PA 613, PA 611, PA 612, PA 614, PA 618, PA 1010, PA 1012, PA 1014 or PA 1018.

[0066] According to one embodiment, powder A and / or powder B is chosen from PA 6 / 12, PA 6 / 66, PA 1010 / 12, 1010 / 11, PA 6 / 12 / 66, PA 6 / 69 / 11 / 12, PA 6 / 66 / 11 / 12, PA 69 / 12, PA 4 / 6, PA 4 / 12, PA 6 / 11, PA 12 / 8, PA11 / 4, PA 11 / 12, PA 8 / 6, PA 8 / 4, PA 12 / 8, PA 12 / 11.

[0067] Preferably, powder A and / or powder B is a homopolyamide 11 or 12 powder.

[0068] Preferably, powder A and / or powder B is a copolyamide 11 or 12 powder.

[0069] According to one embodiment, powder A is a copolyamide 11 powder containing an amino-11-undecanoic monomer, preferably containing a majority monomer of amino-11-undecanoic. Advantageously, the minority comonomer comprises amino-12-dodecanoic, lactam 12, ca-prolactam and / or capryllactam.

[0070] According to one embodiment, powder A is a copolyamide 12 powder containing a monomer of amino-12-dodecanoic acid or a monomer of lactam 12, preferably containing a majority monomer of amino-12-dodecanoic acid or a monomer of lactam 12. Advantageously, the minority comonomer comprises amino-11-undecanoic acid, caprolactam and / or capryllactam.

[0071] According to one embodiment, the minority co-monomer represents from 0.1 to 20% by mass, preferably from 0.5 to 15%, from 1% to 10%, from 1 to 7%, from 1 to 5% by mass of the total mass of the monomer(s) and comonomer(s). Additives

[0072] The additives generally represent less than 5% by mass relative to the total mass of the composition. Preferably, the additives represent less than 3%, preferably less than 2% of the total mass of the composition.

[0073] Among the additives, mention may be made of flow agents, stabilizing agents (light, in particular UV, and heat), optical brighteners, dyes, pigments, energy absorbing additives (including UV absorbers), a wax (for example, a wax of polyethylene and polypropylene, polytetrafluoroethylene, ketones, acid, partially esterified acid, acid anhydride, ester, aldehydes, amides, their derivatives as well as their mixtures) and / or surfactants.

[0074] Among the flow agents, mention may be made, for example, of a hydrophilic silica or hydrophobic. Advantageously, the flow agent represents from 0.01 to 0.4% by mass relative to the total mass of composition. In other embodiments, the powdery composition does not comprise a flow agent.

[0075] The pigment may be, for example for HSS or MJF technology, a pigment having an absorbance of light with a wavelength of 1000 nm, as measured according to ASTM E1790, of less than 40%. Charges

[0076] The thermoplastic polymer powder composition may also comprise one or more fillers. The fillers generally represent less than 40% by mass, in particular less than 30% by mass, and preferably less than 25% by mass relative to the total mass of the final powder composition. Among the fillers, there may be mentioned reinforcing fillers, in particular mineral fillers such as carbon black, talc, nanotubes, carbon or not, and fibers, in particular glass or carbon fibers, ground or not, or even glass in another form, for example in the form of flakes or beads, hollow or not. Other fillers providing an additional property may be used without departing from the scope of the invention, for example flame-retardant fillers, fillers providing electrical or thermal conductivity.

[0077] Process for preparing the composition of the powders

[0078] According to one aspect, the invention relates to a method for manufacturing the composition of powders as described above, by mixing: i. a thermoplastic polymer powder A; ii. 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, relative to the total mass of the composition, of a polyamide B powder, the powder B having - a melting temperature (Tf) lower than or equal to, preferably lower than, the Tf of powder A, the Tf being measured according to standard NF EN ISO 11357-3:2018; and / or - a volume flow index (MVR) ratio of powder B to volume flow index (MVR) of powder A being greater than 5, preferably greater than 10, even more preferably greater than 20, the MVR being measured according to the ISO 1133 standard;

[0079] iii. optionally one or more additives and / or one or more fillers.

[0080] The mixing may typically be achieved by dry mixing.

[0081] According to one embodiment, the method for manufacturing the powder composition as described above is carried out by mixing: i. 59.5 to 99.5% by mass of a thermoplastic polymer powder A; ii. 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, relative to the total mass of the composition, of a thermoplastic polymer powder B, the powder B having - a melting temperature (Tf) lower than or equal to, preferably lower than, the Tf of powder A, the Tf being measured according to standard NF EN ISO 11357-3:2018; and / or - a volume flow index (MVR) ratio of powder B to volume flow index (MVR) of powder A being greater than 5, preferably greater than 10, even more preferably greater than 20, the MVR being measured according to the ISO 1133 standard; - 0 to 40% by mass, preferably 0.05 to 40% by mass of one or more additives and / or one or more fillers,

[0082] relative to the total mass of the composition.

[0083] The thermoplastic polymer powders A and B can be manufactured according to the usual processes.

[0084] Typically, the powder A and / or B contained in the composition can be obtained by grinding thermoplastic polymers in the form of extruded granules or flakes, according to conventional techniques.

[0085] The grinding may be grinding at room temperature.

[0086] The grinding may be cryogenic grinding. In this process, the material to be ground is cooled, for example by liquid nitrogen, liquid carbon dioxide or liquid helium, to make the material easier to grind.

[0087] The grinding can be carried out on equipment known for this purpose, for example by means of a counter-rotating pin mill, a hammer mill or in a whirl mill.

[0088] The powder A and / or B contained in the composition can obviously be obtained by any other process other than the grinding process known to those skilled in the art.

[0089] According to a certain method of preparation, the thermoplastic polymer powder may be subjected to different treatments, in particular thermal or hydraulic treatments. Reference may be made in particular to patent application EP 1413595 AL

[0090] When the powder comprises, in addition to the polymer powders, one or more additives and / or one or more fillers, preferably reinforcing and / or flame-retardant fillers, these additives and / or fillers can be incorporated by mixing in the molten state, for example by extrusion (compounding) and granulation followed by grinding of the granules.

[0091] Preferably, the additives and / or fillers are added by dry blending.

[0092] According to one embodiment, the step of introducing the additives and / or fillers can be carried out during the synthesis of powder A and / or B.

[0093] For example, it is possible to mix polymer A or polymer B by means of a co-precipitation of the polymer from a solution in the presence of certain additives and / or fillers (dissolution / precipitation). The conditions can be easily adapted by those skilled in the art. For example, reference may be made to document EP 0863174 Bl.

[0094] It is also possible to use several of these methods, depending on the additives, for their introduction into the polymer powder.

[0095] The additives and / or fillers may be used in any form suitable according to the preparation method.

[0096] According to one embodiment, one or more additives / fillers are used in powder form. The shape and size of the particles forming the powder is not particularly limited, except by the application of 3D printing by sintering. The particles most often have a spherical shape. But their use in other forms such as in the form of rods or in lamellar form is not excluded.

[0097] When the additives / fillers are added to the polymer in dry-blend, they advantageously have a volume median diameter Dv50 substantially equal to or less than that of the powder with which it will be mixed. 3D printing process by sintering

[0098] The process which is the subject of the invention may in particular be a selective laser sintering (SLS) process, a sintering process of the MJF (Multi Jet Fusion) type or a sintering process of the HSS (High Speed ​​Sintering) type.

[0099] The SLS process is widely known. In this context, reference may be made in particular to documents US 6,136,948 and WO 96 / 06881.

[0100] In this type of process, a thin layer of powder is deposited on a horizontal plate held in an enclosure heated to a temperature called the build temperature. Most often, heating to the build temperature is carried out by means of IR radiation lamps, for example halogen lamps, which generally have an emission maximum at a wavelength between 750 nm and 1250 nm. The build temperature refers to the temperature to which the powder bed, of a constituent layer of a three-dimensional article under construction, is heated during the layer-by-layer sintering process of the powder.Electromagnetic radiation, for example in the form of a laser, then provides the energy necessary to sinter the powder particles at different points in the powder layer according to a geometry corresponding to an object, for example using a computer that stores the shape of an object and reproduces it in the form of slices. Then, the horizontal plate is lowered by a height corresponding to the thickness of a powder layer, and a new layer of powder is spread, heated and then sintered in the same way. The procedure is repeated until . that the object was made.

[0101] The layer of powder deposited on a horizontal plate may have, before sintering, for example a thickness of 20 to 200 μm, and preferably 50 to 150 μm. After sintering, the thickness of the layer of agglomerated material is a little lower, and may have for example a thickness of 10 to 150 μm, and preferably 30 to 120 μm.

[0102] For the MJF and HSS process, the entire layer of the build material is exposed to radiation, but only a portion covered with a fusing agent is melted to become a layer of a 3D part. The fusing agent is a compound capable of absorbing radiation and converting it into thermal energy, for example, a black ink. It is selectively applied to the selected region of the build material. The fusing agent is capable of penetrating the layer of the build material and transmits the absorbed energy to the neighboring build material, thereby causing it to melt or be sintered. By melting, bonding, and subsequent hardening of each layer of the build material, the object is formed.

[0103] In the particular case of MJF, a detailing agent is further added to the edges of the area to be melted to allow the parts to have better definition.

[0104] Advantageously, the use of the polyamide powder composition described below in these processes does not require any particular modification. On the other hand, it makes it possible to obtain parts having a good surface appearance, in particular lower roughness and better definition.

[0105] Advantageously, the method makes it possible to implement the composition of polyamide powders in several successive constructions. In this case, it can be reused alone or in a mixture with other powders, recycled or not.

[0106] The invention will be further explained in a non-limiting manner using the following Examples. Examples

[0107] The examples below illustrate the present invention without limiting its scope. In the examples, unless otherwise indicated, all percentages and parts are expressed by mass. Granulometry

[0108] The powders were characterized in terms of particle size using a Malvern Insitec laser diffractometer with RT Sizer software, according to ISO 13320:2009.

[0109] Light from a laser is sent onto particles that are moving in the air.

[0110] The measurement is carried out on 30 g of powder. Measurement of the melting temperature (Tf)

[0111] The melting temperature of the powders was measured by DSC on a TA Instruments Q2000 calorimeter, in accordance with standard NF EN ISO 11357-3:2018. The value was determined during the heating step at a rate of 20°C / min during the first heating. MVR measurement

[0112] The MVR is measured by a Zwick MFlow device, manufactured by Zwick, at 235°C under a load of 2.16 kg according to ISO 1133. Measurement of elongation at break

[0113] Elongation at break is measured according to ISO 527-1:2019. Powder compositions

[0114] Powders B1, B-2, B-4, Al and A-2 are polyamide powders marketed by the company Arkema. Their commercial names are indicated in Table 1.

[0115] Powder B-3 was obtained from a polyamide 11 powder marketed by the company ARKEMA under the name Rilsan® Invent Natural. The Rilsan® Invent Natural powder was ground in a mini hammer mill with an internal selector until a powder having a Dv50 of 10 μm was obtained.

[0116] The properties of the powders used in the examples are indicated in the table below.

[0117] [Tableauxl] Powder Powder Tf (°C) MVR (cm3 / 10min) Dv50 (pm) Powder B Powder Bl Polyamide 12 (ORGASOL® 2001 UD NAT 1) 177°C 230 5 Powder B-2 Polyamide 12 (ORGASOL® 2003LS) 181°C 11 42 Powder B-3 Polyamide 11 186°C 340 10 Powder B-4 Polyamide 12 (ORGASOL®2002 ES6 NAT 3) 177°C 51 60 Powder A Powder Al Polyamide 12 (ORGASOL® Invent Smooth) 181°C 10 42 Powder A-2 Polyamide 11 (Rilsan® In vent Natural) 202°C 60 47

[0118] 1% of Powder B was added in bulk to Powder A dry (in “dry-blend”) in a Henschel mixer at a rotation speed of 900 rpm for 100 seconds.

[0119] The compositions of powders tested are indicated in the table below.

[0120] [Tables2] Powder Composition Powder 1 Powder Al Powder Bl Powder 2 Powder A-2 Powder Bl Powder 3 Powder A-2 Powder B-2 Powder 4 Powder A-2 Powder B-3 Powder 5 Powder A-2 Powder B-4 Measurement of elongation at break

[0121] The compositions of Powders Al, A-2, 1 to 4 and were used to manufacture by 3D printing by laser sintering IB XY specimens (IB specimen according to the ISO 527-1:2019 standard, called “XY” because printed in the plane of the printer, i.e. horizontally) on a P1000 machine (marketed by the company Prodways) by setting the thickness of the powder layer to 100 μm. The printing parameters used are as follows:

[0122] Laser power: 24W

[0123] Laser speed: 3000mm / s

[0124] Distance between two laser passes: 0.25mm

[0125] The results obtained are gathered in the two tables below (average over 10 specimens tested).

[0126] [Tables3] Construction temperature 170°C 172°C 174°C Elongation at break (%) Powder A-1 (comparative example) N / A 6.8 8.8 Powder 1 8.1 9.8 12.0

[0127] It was observed, at different construction temperatures, that Powder 1 of the invention exhibits an improved elongation at break, compared to the powder without the auxiliary powder (Powder Al).

[0128] On the other hand, advantageously, it was possible to transform Powder 1 at a lower temperature (at 170°C), compared to Powder AL. Thus, the addition of 1% of Powder Bl made it possible to widen the working window, and even more advantageously towards low temperatures, which brings a benefit on a lesser evolution of the powder, which will promote its reuse in another printing test.

[0129] [Tables4] Construction temperature 189°C 191°C 193°C Elongation at break (%) Powder A-2 (comparative example) 22.5 26.2 29.5 Powder 2 36.1 45.8 / Powder 3 31.4 39.6 48.3 Powder 4 28.3 37.6 42.3 Powder 5 30.8 39.8 39.0

[0130] An improvement in elongation at break was observed for Powder 2, Powder 3, Powder 4 and Powder 5, compared to Powder A-2, which does not contain auxiliary powder.

Claims

Claims

1. A polyamide powder composition comprising: i. a thermoplastic polymer powder A; ii. 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, relative to the total mass of the composition, of a thermoplastic polymer powder B, powder B having - a melting point (Tf) less than or equal to, preferably less than, the Tf of powder A, the Tf being measured according to standard NF EN ISO 11357-3:2018; and / or - a ratio of the volume flow index (MVR) of powder B to the volume flow index (MVR) of powder A greater than 5, preferably greater than 10, even more preferably greater than 20, the MVR being measured according to standard ISO 1133.

2. Composition according to claim 1 comprising, relative to the total mass of the composition: i. 59.5 to 99.5% by mass of the thermoplastic polymer powder A; ii. 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, of the thermoplastic polymer powder B; iii. 0 to 40% by mass, preferably 0.05 to 40% by mass of one or more additives and / or one or more fillers.

3. Composition according to claim 1 or 2, in which the thermoplastic polymer powders A and B are chosen from polyolefins such as polypropylene and polyethylene (olefin base waxes would not depart from the scope of the present invention), polycarbonate, polymethylmethacrylate (PMMA), polyamides and thermoplastic elastomers such as polyether block amides (PEBA), polyesters and polyether blocks (COPE), thermoplastic polyurethanes (TPU) and their mixtures, preferably polyamides.

4. Composition according to one of the preceding claims, in which powder A and / or powder B is a polyamide powder, preferably, powders A and B are polyamide powders, even more preferably, chosen from polyamide 11 and polyamide 12 powders.

5. Composition according to one of the preceding claims, in which powder A and / or powder B is a homopolyamide 11 or 12 powder or a copolyamide 11 or 12 powder.

6. Composition according to one of the preceding claims, in which powder A has a melting temperature (Tf) less than or equal to 250°C, preferably less than or equal to 210°C and / or powder B has a melting temperature (Tf) less than or equal to 210°C, preferably between 80 and 210°C, preferably between 100 and 200°C.

7. Composition according to one of the preceding claims, in which the MVR of powder B is greater than 50 cmVIOmin, preferably greater than 100 cmVIOmin, even more preferably greater than 200 cmVIOmin.

8. Composition according to one of the preceding claims, in which powder A has a Dv50 of 20 to 100 pm, preferably 30 to 80 pm, even more preferably 40 to 60 pm, and / or powder B has a Dv50 of 1 to 60 pm, preferably 3 to 50 pm, even more preferably 4 to 20 pm.

9. Composition according to one of the preceding claims, in which the Dv50 of powder B is lower than the Dv50 of powder A, preferably the Dv50 of powder B is 5 to 80% of the Dv50 of powder A, preferably 10 to 60% of the Dv50 of powder A.

10. A method of manufacturing the powder composition, by mixing: i. a thermoplastic polymer powder A; ii. 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, relative to the total mass of the composition, of a polyamide powder B, the powder B having - a melting point (Tf) less than or equal to, preferably less than, the Tf of the powder A, the Tf being measured according to standard NF EN ISO 11357-3:2018; and / or - a ratio of the volume flow index (MVR) of the powder B to the volume flow index (MVR) of the powder A greater than 5, preferably greater than 10, even more preferably greater than 20, the MVR being measured according to ISO 1133, iii. possibly one or more additives and / or one or more fillers.

11. A method according to claim 10, being carried out by mixing: i. 59.5 to 99.5% by mass of the thermoplastic polymer powder A; ii. 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, relative to the total mass of the composition, of the thermoplastic polymer powder B; iii. 0 to 40% by mass, preferably 0.05 to 40% by mass of one or more additives and / or one or more fillers, relative to the total mass of the composition.

12. A method according to claim 10 or 11, the mixing being carried out by dry mixing.

13. A 3D printing method, preferably an electromagnetic radiation-induced sintering method, using at least in part a powder composition according to one of claims 1 to 9.

14. Manufactured article obtained by the 3D printing process of claim 13.

15. Use of 0.1 to 3% by mass, preferably 0.5 to 2% by mass, more preferably 0.7 to 1.5% by mass, relative to the total mass of the composition, of a thermoplastic polymer powder B, preferably a polyamide powder, in a composition containing a thermoplastic polymer powder A, preferably a polyamide powder, in a 3D printing process, preferably by sintering, powder B having - a melting point (Tf) less than or equal to, preferably less than, the Tf of powder A, the Tf being measured according to standard NF EN ISO 11357-3:2018; and / or - a ratio of the volume melting index (MVR) of powder B to the volume melting index (MVR) of powder A greater than 5, preferably greater than 10, even more preferably greater than 20, the MVR being measured according to the ISO 1133 standard; to improve elongation at break.