Composition of thermoplastic polymer powder for 3D printing

Abstract

The present invention relates to a composition of thermoplastic polymer powders for manufacturing articles by 3D printing, particularly by sintering, comprising a mixture of thermoplastic polymer powders, one of which is present in small amounts, and enabling the acquisition of printed parts having improved mechanical properties. The present invention also relates to a method for preparing the powder composition, the use of the composition in a laser sintering manufacturing process, and articles manufactured from the powder composition.

Description

Technology Field

[0001] The present invention relates to a thermoplastic polymer powder composition for manufacturing articles by 3D printing, particularly by sintering, comprising a mixture of thermoplastic polymer powders, one of which is present in small amounts, and enabling the production of printed workpieces having improved mechanical properties.

[0002] The present invention also relates to a method for preparing the powder composition, its use in a manufacturing process by laser sintering, and articles manufactured using the powder composition. Background Technology

[0003] Addition manufacturing on a bed of thermoplastic polymer powder (Selective Laser Sintering (SLS), Multi-Jet Fusion (MJF), High-Speed ​​Sintering (HSS), etc.) enables the building of workpieces with complex geometries in a series. Specifically, this allows for the simultaneous production of multiple workpieces with excellent resolution and very good mechanical properties, which gives them advantages over other addition manufacturing processes such as fused wire deposition.

[0004] Polyamide powders are particularly useful for the aforementioned additional manufacturing techniques. In particular, Orgasol from Arkema. ® , Durafom from 3D-Systems ® , Vestosint from Evonik ® , or PA2200 from EOS ® You may also mention commercial products such as.

[0005] Rilsan from Arkema ® Commercial polyamide 11-based powders such as may also be mentioned.

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

[0007] Workpieces printed from these powders possess favorable mechanical properties. However, to meet increasingly stringent performance requirements over time, there is a continuous need to improve their mechanical properties, particularly fracture properties such as elongation at break. Furthermore, it is known that fracture properties are generally lower after addition manufacturing processes compared to more traditional processes such as injection molding; this reinforces the need to improve fracture properties for addition manufacturing processes. The problem to be solved

[0008] Accordingly, the present invention aims to propose a thermoplastic polymer powder composition comprising at least two different and specifically selected thermoplastic polymer powders, one of which is present in a small amount in the composition (referred to as an “auxiliary powder”), which enables the production of sintered objects having improved mechanical properties, particularly in terms of elongation at break.

[0009] For the purposes of the present invention, two different thermoplastic polymer powders may be powders of the same thermoplastic polymer or two different thermoplastic polymers. The thermoplastic polymer powders differ in at least one of their properties. These properties may include their appearance, such as their particle size, or their thermal properties (e.g., degree of crystallization, properties of crystal phases, melting point, heat of fusion, etc.) or their rheological properties. means of solving the problem

[0010] According to a first embodiment, one object of the present invention is a thermoplastic polymer powder composition comprising the following:

[0011] (i) Thermoplastic polymer powder A;

[0012] (ii) thermoplastic polymer powder B in an amount of 0.1 to 3 mass%, preferably 0.5 to 2 mass%, more preferably 0.7 to 1.5 mass%, based on the total mass of the composition,

[0013] The above powder B has the following:

[0014] - a melting point (Tm) of powder A or lower, preferably less than Tm - where Tm is measured according to the standard NF EN ISO 11357-3:2018 -; and / or

[0015] - The ratio of the melt volume-flow rate (MVR) of powder B to the melt volume-flow rate (MVR) of powder A, which is greater than 3, preferably greater than 5, more preferably greater than 10, MVR is measured according to standard ISO 1133.

[0016] According to another aspect, the subject of the present invention is a thermoplastic polymer powder composition comprising, with respect to the total mass of the composition, the following:

[0017] (i) 59.5 mass% to 99.5 mass% of thermoplastic polymer powder A as defined above;

[0018] (ii) 0.1 to 3 mass%, preferably 0.5 to 2 mass%, more preferably 0.7 to 1.5 mass% of the thermoplastic polymer powder B as defined above;

[0019] (iii) 0 to 40 mass% of one or more additives and / or one or more fillers, preferably 0.05 to 40 mass%.

[0020] The thermoplastic polymer powder composition comprises, with respect to the total mass of the composition, 0.1 mass% to 3 mass%, preferably 0.1 mass% to 2 mass%, 0.1 mass% to 1.8 mass%, 0.1 mass% to 1.5 mass%, 0.5 mass% to 2 mass%, 0.5 mass% to 1.8 mass%, 0.5 mass% to 1.5 mass%, 0.7 mass% to 1.5 mass%, 0.9 mass% to 1.5 mass%, 1 mass% to 1.5 mass%, or 0.9 mass% to 1.4 mass% of powder B.

[0021] According to one embodiment, the melting point (Tm) of powder B is at least 1°C lower than the melting point of powder A, and preferably at least 3°C ​​lower than the melting point of powder A or at least 10°C lower than the melting point of powder A.

[0022] According to one embodiment, the difference between the melting points of powder B and powder A is 30°C or less.

[0023] According to one embodiment, the Tm of powder B is the same as the Tm of powder A, and the ratio of powder B MVR to powder A MVR is greater than 3, preferably greater than 5, more preferably greater than 10, even more preferably greater than 20, and the MVR is measured according to standard ISO 1133.

[0024] According to one embodiment, powder B has a melting point lower than the Tm of powder A and a ratio of powder B MVR to powder A MVR greater than 3, preferably greater than 5, more preferably greater than 10, and even more preferably greater than 20, and the MVR is measured according to standard ISO 1133.

[0025] Thermoplastic polymer powder B, which may be used in the context of the present invention, may be selected from polyolefins such as polypropylene and polyethylene (olefin-based base waxes will not be excluded from the context of the present invention), polycarbonates, polymethyl methacrylate (PMMA), polyamides and thermoplastic elastomers, such as polyether block amides (PEBA), polyesters having polyether blocks (COPE), thermoplastic polyurethanes (TPU) and mixtures thereof, PAEKs such as PEKK and PEEK-based copolymers, preferably polyamides and polyether block amides, more preferably polyamides.

[0026] The thermoplastic polymer of powder B is typically a semicrystalline thermoplastic polymer.

[0027] According to one embodiment, the thermoplastic polymer powder used in the context of the present invention is selected from polyolefins such as polypropylene and polyethylene (olefin-based base waxes will not be excluded from the context of the present invention), polyamides and polyether block amides (PEBAs), polyesters having polyether blocks (COPEs), thermoplastic elastomers such as thermoplastic polyurethanes (TPUs), and mixtures thereof, preferably polyamides and polyether block amides, more preferably polyamides.

[0028] Accordingly, according to a specific embodiment of the present invention, the present invention aims to provide a polyamide powder composition comprising at least two different and specifically selected polyamide powders, one of which is present in a small amount in the composition (referred to as an “auxiliary powder”), which enables the production of sintered objects having improved mechanical properties, particularly in terms of elongation at break.

[0029] Preferably, powder A and / or powder B is a polyamide powder; preferably, powder A and powder B are polyamide powders.

[0030] According to one embodiment, powder A is a polyamide 12 or polyamide 11 powder.

[0031] According to one embodiment, powder B is a polyamide 12 or polyamide 11 powder.

[0032] According to one embodiment, if powder A is a polyamide 11 powder, powder B is a polyamide 11 powder or a polyamide 12 powder.

[0033] According to one embodiment, if powder A is polyamide 12 powder, powder B is polyamide 12 powder.

[0034] According to one embodiment, powder A has a melting point (Tm) of 250°C or lower, preferably 210°C or lower.

[0035] According to one embodiment, powder B has a melting point (Tm) of 210°C or lower, preferably between 80°C and 210°C, preferably between 100°C and 200°C.

[0036] The melt volume-flow rate (MVR) of powder B is 50 cm³ 3 / 10 min exceeding, preferably 100 cm 3 / 10 min exceeding, more preferably 200 cm 3 It exceeds / 10 min.

[0037] According to one embodiment, powder A has a Dv50 of 20 μm to 100 μm, preferably 30 μm to 80 μm, more preferably 40 μm to 60 μm.

[0038] According to one embodiment, powder B has a Dv50 of 1 μm to 60 μm, preferably 3 μm to 50 μm, more preferably 4 μm to 20 μm.

[0039] The Dv50 of powder B may be greater than, less than, or equal to the Dv50 of powder A.

[0040] Preferably, the Dv50 of powder B is less 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.

[0041] In the context of the present invention, it has been observed that adding a small amount of a specific auxiliary powder to a thermoplastic polymer powder suitable for 3D printing by sintering, particularly a polyamide powder, surprisingly results in the production of sintered objects having improved mechanical properties, particularly in terms of improved elongation at break.

[0042] The present invention also relates to a 3D printing process, preferably a sintering process induced by electromagnetic radiation, using a powder as defined above, or a powder comprising a portion of said non-aggregating powder recovered after one or more builds in the same printing process or a different printing process.

[0043] Electromagnetic radiation is preferably selected from one or more laser beams, infrared radiation, or UV radiation.

[0044] The present invention also relates to an article obtained by a 3D printing process as defined above.

[0045] The articles may be selected from prototypes, models, and parts, and may be selected particularly from the fields of automotive, marine, aviation, aerospace, medical (prosthetics, auditory systems, cell tissues, etc.), textiles, clothing, fashion, decoration, design, electronic housing, telephone, computing, lighting, sports, and industrial tools.

[0046] According to another aspect, the present invention relates to the use of a thermoplastic polymer powder B in an amount of 0.1 to 3 mass%, preferably 0.5 to 2 mass%, more preferably 0.7 to 1.5 mass% with respect to the total mass of a composition containing a thermoplastic polymer powder A, in a 3D printing process by sintering, preferably for improving elongation at break, said powder B has the following:

[0047] - a melting point (Tm) of powder A or lower, preferably less than Tm - where Tm is measured according to the standard NF EN ISO 11357-3:2018 -; and / or

[0048] - The ratio of the melt volume-flow rate (MVR) of powder B to the melt volume-flow rate (MVR) of powder A, which is greater than 3, preferably greater than 5, more preferably greater than 10, MVR is measured according to standard ISO 1133.

[0049] Thermoplastic polymer powders are preferably polyamide powders.

[0050] The present invention is now described in detail and without limitation in the following description. Specific details for implementing the invention

[0051] definition

[0052] In this description of the present invention, including the following examples:

[0053] " powder The term is understood to refer to a solid material in a finely divided form; this is generally provided in the form of very small particles, typically on the order of several hundred micrometers or less.

[0054] Here Volume-central diameter Also referred to as Dv50 ..., for example, Malvern Insitec ®On a diffractometer, when measured by laser scattering according to standard ISO 13320: 2009, it corresponds to a particle size value that divides a group of inspected particles into exactly two.

[0055] " melting point The term (Tm) indicates the temperature at which a compound that is at least partially crystalline transitions into a viscous liquid state when measured according to the 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.

[0056] Unless otherwise indicated, this is the peak melting temperature as defined below.

[0057] More specifically, the following terms are understood in relation to the melting point:

[0058] " peak " is a portion of the thermal analysis obtained by differential scanning calorimetry (DSC) that deviates from the specimen's baseline, reaches a maximum or minimum value, and then returns to the specimen's baseline. Such a peak may indicate a first-order transition;

[0059] " base line " indicates the portion of the recorded thermal analysis where there is no arbitrary transition, specifically in this case, the portion where there is no arbitrary first-order transition of the melt type. It is possible to determine a virtual baseline within the transition zone: this is a virtual 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 specimen's baseline with a straight line;

[0060] " Peak melting point It displays the temperature at which the distance between the thermal analysis diagram and the virtual baseline is greatest during the peak.

[0061] Melt Volume-to-Flow Rate (MVR)It is measured using a Zwick MFlow measuring machine manufactured by Zwick in accordance with the ISO 1133 standard.

[0062] Breaking elongation It is measured according to the standard ISO 527-1: 2019.

[0063] In this description, it is noted that when ranges are mentioned, expressions of the type “between ~ and ~” or “~ to ~” include the limit values ​​of the ranges.

[0064] Unless otherwise noted, the expressed percentages are mass percentages. Unless otherwise noted, the parameters mentioned are measured at atmospheric pressure and ambient temperature (23°C).

[0065] Thermoplastic polymer powder composition

[0066] Thermoplastic polymer powders A and B

[0067] Thermoplastic polymer powders A and B may be powders that are commercially available on the market.

[0068] In particular, Orgasol from Arkema ® , Durafom from 3D-Systems ® , Vestosint from Evonik ® , or PA2200 from EOS ® You may also mention commercial products such as.

[0069] Rilsan from Arkema ® Commercial polyamide 11-based powders such as Invent may also be mentioned.

[0070] Kepstan from Arkema ® Commercial PEKK-based powders such as those mentioned may also be mentioned.

[0071] Thermoplastic polymer powders A and B can be obtained through any suitable process known to those skilled in the art.

[0072] Preferably, powder A and / or powder B is a polyamide powder.

[0073] Preferably, powders A and B are polyamide powders, and more preferably are selected from polyamide 11 and polyamide 12 powders.

[0074] The polyamides of the present invention may be homopolyamides or copolyamides.

[0075] For the purposes of the present invention, the term "homopolyamide" means polymerization products of aminocarboxylic acids, lactams or diacid monomers and diamines.

[0076] For the purposes of the present invention, the term “copolyamide” means a copolymer derived from the polymerization of at least two different monomers referred to as “comonomers,” namely, at least one monomer selected from aminocarboxylic acids, lactams, and diamine-disan pairs, and at least one comonomer (a monomer different from the first monomer). The copolyamide may comprise a “major” monomer that represents at least 80% of the total mass of the mixture of monomers, and at least one “auxiliary” comonomer that represents 20% or less of the total mass of the mixture of monomer(s) and comonomer(s).

[0077] In the following description, the term "monomer" should be understood to mean a "repeating unit." A special case is when the repeating unit consists of a combination of a diacid and a diamine. The monomer is considered to correspond to a combination of a diamine and a diacid, namely a diamine-diacid pair (equimolar). This is explained by the fact that, individually, a diacid or a diamine is merely a structural unit and is not sufficient on its own to form a polymer.

[0078] Examples of monomers of the amino acid or aminocarboxylic acid type may be mentioned, such as aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanic acid, n-heptyl-11-aminoundecanic acid and 12-aminododecanoic acid, which contain 4 to 18 carbon atoms.

[0079] Examples of lactam-type monomers may be mentioned that may contain 3 to 18 carbon atoms on the main ring and may be substituted. For example, β,β-dimethylpropiolactam, α,α-dimethylpropiolactam, amyloractam, caprolactam also known as lactam 6, caprylactam also known as lactam 8, enantholactam, 2-pyrrolidone, and lauryllactam also known as lactam 12 may be mentioned.

[0080] Examples of dicarboxylic acids may be mentioned, including acids containing between 4 and 18 carbon atoms. Examples that may be mentioned include adipic acid, sebacic acid, azelaic acid, souveric acid, isophthalic acid, butanedioic acid, 1,4-cyclohexyldicarboxylic acid, terephthalic acid, sodium or lithium salt of sulfoisophthalic acid, dimeric fatty acids (such dimeric fatty acids have a dimer content of at least 98% and are preferably hydrogenated), and dodecandioic acid.

[0081] Examples of diamines may be mentioned as aliphatic diamines containing 4 to 18 atoms, which may be aryl and / or saturated cyclic. Examples that may be mentioned include hexamethylenediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, 5-dodecamethylenediamine, 1,5-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, polyol diamines, isophoronediamine (IPD), methylpentamethylenediamine (MPDM), bis(aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), meta-xylylenediamine, bis(p-aminocyclohexyl)methane, and trimethylhexamethylenediamine.

[0082] According to one embodiment, powder A is a polyamide powder that may be a homopolyamide or a copolyamide.

[0083] According to one embodiment, powder B is a polyamide powder that may be homopolyamide or copolyamide.

[0084] According to one embodiment, powder A and / or powder B are selected 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.

[0085] According to one embodiment, powder B is selected from PA 6 / 12, PA 6 / 66, PA 1010 / 12, PA 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, PA 11 / 4, PA 11 / 12, PA 8 / 6, PA 8 / 4, PA 12 / 8 and PA 12 / 11.

[0086] Preferably, powder A and / or powder B is homopolyamide 11 or 12 powder.

[0087] Preferably, powder A and / or powder B is a copolyamide 11 or 12 powder.

[0088] According to one embodiment, powder A is a copolyamide 11 powder containing an 11-aminoundecanic acid monomer, preferably containing an 11-aminoundecanic acid major monomer. Advantageously, the auxiliary comonomer comprises 12-aminododecanoic acid, lactam 12, caprolactam and / or capryllactam.

[0089] According to one embodiment, powder A is a copolyamide 12 powder containing a 12-aminododecanoic acid monomer or a lactam 12 monomer, preferably containing a 12-aminododecanoic acid major monomer or a lactam 12 monomer. Advantageously, the auxiliary comonomer comprises 11-aminoundecanoic acid, caprolactam, and / or capryllactam.

[0090] According to one embodiment, the auxiliary comonomer represents 0.1 mass% to 20 mass%, preferably 0.5 mass% to 15 mass%, 1 mass% to 10 mass%, 1 mass% to 7 mass%, and 1 mass% to 5 mass% with respect to the total mass of the monomer(s) and comonomer(s).

[0091] Additives

[0092] The additives generally represent less than 5 mass% of the total mass of the composition. Preferably, the additives represent less than 3 mass% and preferably less than 2 mass% of the total mass of the composition.

[0093] Among the additives, fluids, stabilizers (light, particularly UV, and thermal stabilizers), optical brighteners, dyes, pigments, energy-absorbing additives (including UV absorbers), waxes (e.g., polyethylene and polypropylene waxes, polytetrafluoroethylene wax, ketone waxes, acid waxes, partially esterified acid waxes, acid anhydride waxes, ester waxes, aldehyde waxes, amide waxes, derivatives thereof and also mixtures thereof) and / or surfactants may be mentioned.

[0094] Among the fluidizers, for example, hydrophilic or hydrophobic silica may be mentioned. The fluidizer advantageously represents 0.01 mass% to 0.4 mass% with respect to the total mass of the composition. In other embodiments, the powdered composition does not contain any fluidizer.

[0095] The pigment may be a pigment that has an absorbance of less than 40% of light having a wavelength of 1000 nm when measured according to standard ASTM E1790, for example, for HSS or MJF technology.

[0096] Fillers

[0097] The polymer powder composition may also include one or more fillers. The fillers generally represent less than 40 mass%, particularly less than 30 mass%, and preferably less than 25 mass% with respect to the total mass of the final powder composition. Among the fillers, reinforcing fillers, particularly inorganic fillers such as carbon black, talc, carbon or non-carbon nanotubes, and fibers, particularly ground or unground glass or carbon fibers, or other forms of glass such as flakes or hollow or filled beads, may be mentioned. Other fillers providing additional properties may be used without departing from the scope of the invention, such as flame-retardant fillers, or fillers providing electrical or thermal conductivity.

[0098] Method for preparing a powder composition

[0099] According to one embodiment, the present invention relates to a method for preparing a powder composition as described above by mixing the following:

[0100] i. Thermoplastic polymer powder A;

[0101] ii. Polyamide powder B in an amount of 0.1 mass% to 3 mass%, preferably 0.5 mass% to 2 mass%, more preferably 0.7 mass% to 1.5 mass%, based on the total mass of the composition,

[0102] iii. Optionally, one or more additives and / or one or more fillers,

[0103] The above powder B has the following:

[0104] - a melting point (Tm) of powder A or lower, preferably less than Tm - where Tm is measured according to the standard NF EN ISO 11357-3:2018 -; and / or

[0105] - The ratio of the melt volume-flow rate (MVR) of powder B to the melt volume-flow rate (MVR) of powder A, which is greater than 3, preferably greater than 5, more preferably greater than 10, MVR is measured according to standard ISO 1133.

[0106] Mixing may also typically be performed by dry blending.

[0107] According to one embodiment, the process for preparing a powder composition as described above is carried out by mixing the following with respect to the total mass of the composition:

[0108] (i) 59.5 mass% to 99.5 mass% of thermoplastic polymer powder A;

[0109] (ii) 0.1 to 3 mass%, preferably 0.5 to 2 mass%, more preferably 0.7 to 1.5 mass% of thermoplastic polymer powder B with respect to the total mass of the composition,

[0110] 0 to 40 mass% of one or more additives and / or one or more fillers, preferably 0.05 to 40 mass%,

[0111] Powder B has the following:

[0112] - a melting point (Tm) of powder A or lower, preferably less than Tm - where Tm is measured according to the standard NF EN ISO 11357-3:2018 -; and / or

[0113] - The ratio of the melt volume-flow rate (MVR) of powder B to the melt volume-flow rate (MVR) of powder A, which is greater than 3, preferably greater than 5, more preferably greater than 10, MVR is measured according to standard ISO 1133.

[0114] Thermoplastic polymer powders A and B can be manufactured according to conventional processes.

[0115] Typically, powders A and / or B contained in the composition may be obtained by milling polymers in the form of extruded pellets or flakes according to conventional techniques.

[0116] Milling can also be milling at ambient temperature.

[0117] Milling may also be cryogenic milling. In this process, the material to be milled is cooled by, for example, liquid nitrogen, liquid carbon dioxide, or liquid helium, making it easier to mill.

[0118] Milling can be performed on equipment known for this purpose, for example, using a counter-rotating pin mill, a hammer mill, or a vortex mill.

[0119] Polymer powders A and B contained in the composition can be obtained through any process other than the milling process known to those skilled in the art.

[0120] According to a specific manufacturing method, the polymer powder may be applied to different treatments, particularly thermal or hydrodynamic treatments, where appropriate. In particular, patent application EP 1413595 A1 may be referenced.

[0121] Where the powder comprises, in addition to the polymer powders, one or more additives and / or one or more fillers, preferably reinforcing fillers or flame retardants, these additives and / or fillers may be incorporated, for example, by melt blending by extrusion (compounding) and granulation, followed by milling of pellets.

[0122] Preferably, additives and / or fillers are added to the powder by dry blending.

[0123] According to one embodiment, the step of introducing additives and / or fillers may be performed during the synthesis of powders A and / or B.

[0124] For example, it is possible to mix polymer A or polymer B by co-precipitation (dissolution / precipitation) of the polymer from a solution in the presence of specific additives and / or fillers. Conditions can be easily adapted by those skilled in the art. For example, reference may be made to EP 0863174 B1.

[0125] In addition, depending on the additives, it is possible to use several of these processes to introduce them into the polymer powder.

[0126] Additives and / or fillers may be used in any suitable form depending on the manufacturing method.

[0127] According to one embodiment, one or more additives / fillers are used in powder form. The shape and size of the particles forming the powder are not particularly limited, except in the case of 3D printing by sintering. The particles typically have a spherical shape. However, their use in other shapes, such as rods or lamellar shapes, is not excluded.

[0128] When additives / fillers are added to a polymer by dry-blending, they advantageously have a volume-center diameter Dv50 that is substantially smaller than or equal to the volume-center diameter Dv50 of the powder to be mixed.

[0129] 3D printing process by sintering

[0130] The process subject to the present invention may be, in particular, a selective laser sintering (SLS) process, a multi-jet fusion (MJF) type sintering process, or a high-speed sintering (HSS) type sintering process.

[0131] The SLS process is widely known. In this context, US 6 136 948 and WO 96 / 06881 may be mentioned in particular.

[0132] In this type of process, a thin layer of powder is deposited onto a horizontal plate held within a chamber heated to a temperature called the build temperature. Typically, heating to the build temperature is performed by IR radiation lamps, for example, halogen lamps having emission peaks at wavelengths generally between 750 nm and 1250 nm. The build temperature indicates the temperature at which the powder bed of the constituent layers of the three-dimensional article being built is heated during the process for the layer-by-layer sintering of the powder. Electromagnetic radiation, for example in the form of a laser, provides the energy necessary to sinter powder particles at different points on the powder layer according to the geometry corresponding to the object, using, for example, a computer that holds the shape of the object in memory and reconstructs the shape in the form of slices. Subsequently, the horizontal plate is lowered by a height corresponding to the thickness of the powder layer, a new powder layer is spread out, heated, and then sintered in the same manner. The procedure is repeated until the object is manufactured.

[0133] The powder layer deposited on the horizontal plate may have a thickness of, for example, 20 to 200 μm and preferably 50 to 150 μm before sintering. After sintering, the thickness of the layer of aggregated material is slightly lower, for example, 10 to 150 μm and preferably 30 to 120 μm.

[0134] In MJF and HSS processes, the entire layer of the build material is exposed to radiation, but only the portion covered by the flux is melted to form the layer of the 3D workpiece. The flux is a compound capable of absorbing radiation and converting it into thermal energy, such as black ink. It is selectively applied to selected areas of the build material. The flux can penetrate into the layer of the build material and transfer the absorbed energy to neighboring build materials, thereby causing them to melt or sinter. An object is formed through the melting, bonding, and subsequent curing of each layer of the build material.

[0135] In certain cases of MJF, additional detailing is added to the edges of the melting zone to provide better clarity to the workpieces.

[0136] Advantageously, the use of the polyamide powder composition described below in these processes does not require any specific modifications. However, this enables obtaining workpieces with good surface appearance, particularly lower roughness and better clarity.

[0137] Advantageously, the process enables the use of polyamide powder compositions in multiple continuous builds. In this case, it can be reused either alone or blended with other recycled or non-recycled powders.

[0138] The present invention will be further explained in a non-limiting manner with the help of the following examples.

[0139] Examples

[0140] The following examples illustrate the invention without limiting the scope of the invention. In the examples, unless otherwise indicated, all percentages and parts are expressed in terms of mass.

[0141] particle size

[0142] The powders were characterized in terms of particle size using a Malvern Insitec laser diffractometer equipped with RT Sizer software according to standard ISO 13320:2009.

[0143] Light from the laser was sent onto particles moving in the air.

[0144] The measurement is performed on 30 g of powder.

[0145] Measurement of melting point (Tm)

[0146] The melting points of the powders were measured by DSC on a Q2000 calorimeter from TA instruments in accordance with the standard NF EN ISO 11357-3:2018. The values ​​were determined during the heating phase at a rate of 20°C / min during the first heating.

[0147] MVR measurement

[0148] MVR is measured using a Zwick MFlow machine manufactured by Zwick at 235°C under a load of 2.16 kg in accordance with standard ISO 1133.

[0149] Measurement of elongation at break

[0150] The elongation at break is measured according to the standard ISO 527-1: 2019.

[0151] Powder compositions

[0152] Powders B-1, B-2, B-4, A-1, and A-2 are polyamide powders sold by the company Arkema. Their brand names are shown in Table 1.

[0153] Powder B-3 is Rilsan ® It was obtained from polyamide 11 powder sold by the company Arkema under the name Invent Natural. Rilsan ®Invent Natural powder was milled in a hammer mill equipped with an internal selector until a powder having a Dv50 of 10 μm was obtained.

[0154] The characteristics of the powders used in the examples are shown in the table below.

[0155]

[0156] 1 mass% of powder B was added to powder A and dry-blended in a Henschel mixer at a rotational speed of 900 rpm for 100 seconds.

[0157] The tested powder compositions are shown in the table below.

[0158]

[0159] Measurement of elongation at break

[0160] The compositions of powders A-1 and A-2 and powders 1 to 4 were used to manufacture 1B XY specimens (specimen 1B according to standard ISO 527-1:2019, referred to as "XY" because it is printed on the horizontal plane of the printer) by 3D printing by laser sintering on a P1000 machine (sold by Prodways) while controlling the powder layer thickness to 100 μm. The printing parameters used are as follows:

[0161] Laser Power: 24 W

[0162] Laser speed: 3000 mm / s

[0163] Distance between 2 laser paths: 0.25 mm

[0164] The results are listed together in the two tables below (average of 10 tested specimens).

[0165]

[0166] It was observed that at various build temperatures, powder 1 of the present invention has an improved elongation at break compared to powder without auxiliary powder (powder A-1).

[0167] Furthermore, advantageously, powder 1 was successfully converted at a lower temperature (at 170°C) compared to powder A-1. Thus, the addition of 1% of powder B-1 allowed the working window to be widened, and more advantageously, to lower temperatures, which brings advantages in terms of less variation of the powder, which promotes its reuse in other printing tests.

[0168]

[0169] Compared to powder A-2 which does not contain any auxiliary powder, an improvement in elongation at break was observed for powders 2, 3, 4, and 5.

Claims

Claim 1 A thermoplastic polymer powder composition comprising: (i) a thermoplastic polymer powder A; and (ii) a thermoplastic polymer powder B in an amount of 0.1 to 3 mass%, preferably 0.5 to 2 mass%, more preferably 0.7 to 1.5 mass% with respect to the total mass of the composition, wherein the powder B has: - a melting point (Tm) of the powder A, preferably less than or equal to the melting point (Tm) of the powder A, said Tm being measured according to the standard NF EN ISO 11357-3:2018; and / or - a ratio of the melt volume-flow rate (MVR) of the powder B to the melt volume-flow rate (MVR) of the powder A being greater than 3, preferably greater than 5, more preferably greater than 10, said MVR being measured according to the standard ISO 1133. Claim 2 A thermoplastic polymer powder composition according to claim 1, comprising, with respect to the total mass of the composition, (i) 59.5 mass% to 99.5 mass% of the thermoplastic polymer powder A; (ii) 0.1 mass% to 3 mass%, preferably 0.5 mass% to 2 mass%, more preferably 0.7 mass% to 1.5 mass% of the thermoplastic polymer powder B; and (iii) 0 mass% to 40 mass%, preferably 0.05 mass% to 40 mass% of one or more additives and / or one or more fillers. Claim 3 A thermoplastic polymer powder composition according to claim 1 or 2, wherein the thermoplastic polymer powders A and B are selected from polyolefins such as polypropylene and polyethylene (olefin-based base waxes will not be outside the scope of the invention), polycarbonates, polymethyl methacrylate (PMMA), polyamides and thermoplastic elastomers, such as polyether block amides (PEBAs), polyesters having polyether blocks (COPEs), thermoplastic polyurethanes (TPUs), and mixtures thereof, preferably polyamides and polyether block amides, more preferably polyamides. Claim 4 A thermoplastic polymer powder composition according to any one of claims 1 to 3, wherein powder A and / or powder B is a polyamide powder; preferably, powders A and B are polyamide powders, more preferably selected from polyamide 11 and polyamide 12 powders. Claim 5 A thermoplastic polymer powder composition according to any one of claims 1 to 4, wherein powder A and / or powder B is homopolyamide 11 or 12 powder or copolyamide 11 or 12 powder. Claim 6 A thermoplastic polymer powder composition according to any one of claims 1 to 5, wherein the melting point (Tm) of powder A is 250°C or lower, preferably 210°C or lower, and / or the melting point (Tm) of powder B is 210°C or lower, preferably between 80°C and 210°C, preferably between 100°C and 200°C. Claim 7 In any one of claims 1 to 6, the MVR of powder B is 50 cm 3 / 10 min exceeding, preferably 100 cm 3 / 10 min exceeding, more preferably 200 cm 3 Thermoplastic polymer powder composition exceeding / 10 min. Claim 8 A thermoplastic polymer powder composition according to any one of claims 1 to 7, wherein powder A has a Dv50 of 20 μm to 100 μm, preferably 30 μm to 80 μm, more preferably 40 μm to 60 μm, and / or powder B has a Dv50 of 1 μm to 60 μm, preferably 3 μm to 50 μm, more preferably 4 μm to 20 μm. Claim 9 A thermoplastic polymer powder composition according to any one of claims 1 to 8, wherein the Dv50 of powder B is less 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. Claim 10 A method for preparing a powder composition comprising: i. a thermoplastic polymer powder A; ii. a polyamide powder B in an amount of 0.1 mass% to 3 mass%, preferably 0.5 mass% to 2 mass%, more preferably 0.7 mass% to 1.5 mass%, with respect to the total mass of the composition; iii. optionally, by mixing one or more additives and / or one or more fillers, wherein the powder B has a melting point (Tm) that is less than or equal to, preferably less than, the melting point (Tm) of the powder A, said Tm being measured according to the standard NF EN ISO 11357-3:2018; and / or a ratio of the melting volume-flow rate (MVR) of the powder B to the melting volume-flow rate (MVR) of the powder A being greater than 3, preferably greater than 5, more preferably greater than 10, said MVR being measured according to the standard ISO 1133. Claim 11 A method for preparing a powder composition according to claim 10, wherein, with respect to the total mass of the composition, (i) 59.5 mass% to 99.5 mass% of the thermoplastic polymer powder A; (ii) with respect to the total mass of the composition, 0.1 mass% to 3 mass%, preferably 0.5 mass% to 2 mass%, more preferably 0.7 mass% to 1.5 mass% of the thermoplastic polymer powder B; and (iii) 0 mass% to 40 mass%, preferably 0.05 mass% to 40 mass% of one or more additives and / or one or more fillers. Claim 12 A method for preparing a powder composition according to claim 10 or 11, wherein the mixing is performed by dry blending. Claim 13 A 3D printing process that at least partially uses the powder composition described in any one of claims 1 to 9, preferably a sintering process generated by electromagnetic radiation. Claim 14 A manufactured article obtained through the 3D printing process described in Paragraph 13. Claim 15 In a 3D printing process by sintering, preferably for improving elongation at break, the use of a thermoplastic polymer powder B, preferably a polyamide powder, in an amount of 0.1 to 3 mass%, preferably 0.5 to 2 mass%, more preferably 0.7 to 1.5 mass% with respect to the total mass of the composition, wherein the powder B has: - a melting point (Tm) of the powder A, preferably less than or equal to the melting point (Tm) of the powder A, said Tm being measured according to the standard NF EN ISO 11357-3:2018; and / or - a ratio of the melt volume-flow rate (MVR) of the powder B to the melt volume-flow rate (MVR) of the powder A being greater than 3, preferably greater than 5, more preferably greater than 10, said MVR being measured according to the standard ISO 1133.

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