Thermoplastic polymer powders for 3D printing with improved stability and recyclability

Abstract

The present invention relates to a polymer powder comprising a thermoplastic polymer and a specific antioxidant with improved stability and recyclability, in particular for the manufacture of articles by 3D printing by sintering. The invention also relates to a process for preparing this powder and to its use in manufacturing processes by sintering, and to articles manufactured from said powder.

Description

[Technical field]

[0001] The present invention relates to a polymer powder comprising a thermoplastic polymer and a specific antioxidant with improved stability and recyclability, in particular for the manufacture of articles by 3D printing by sintering.

[0002] The invention also relates to a process for preparing this powder and to its use in manufacturing processes by sintering, and to articles manufactured from said powder. [Background technology]

[0003] There are various 3D printing techniques that use polymer powder compositions. The principle is generally based on the coalescence of the powder layer by layer by melting said layer (hereinafter "sintering") caused by electromagnetic waves, for example a laser beam (laser sintering), infrared rays, UV rays or any electromagnetic wave source that makes it possible to melt the powder layer by layer to produce a three-dimensional object.

[0004] Mention may be made of the selective laser sintering (SLS) technique. Mention may also be made of sintering techniques using absorbents, such as those known under the names "high speed sintering" (HSS) and "multi-jet fusion" (MJF).

[0005] For methods of sintering such as SLS or MJF, the use of thermoplastic polymer powders, for example polyamide powders, is preferred.

[0006] During each build in the sintering process, also known as a run, a large portion of the powder is not used (e.g., approximately 85% of the powder is not targeted by the laser in SLS or by the infrared in MJF and is therefore not agglomerated and / or melted), so it is advantageous to be able to reuse, or recycle, this powder during the next build (or next run).

[0007] However, if the sintering process is carried out under air, e.g. in the MJF process, the presence of oxygen at high temperatures can lead to thermo-oxidative degradation of the polymer, causing undesirable yellowing of the powder and, consequently, the printing member, which prevents the unagglomerated powder from being reused.

[0008] To be recyclable, it is necessary to provide thermoplastic polymer powders that have good thermal stability, more particularly in a process for sintering under air.

[0009] For the purposes of this invention, thermal stability means reduced thermo-oxidative degradation; that is to say reduced yellowing of non-agglomerated powders, especially during sintering.

[0010] It is known to employ antioxidants in powder formulations to improve the recyclability of the powder and / or to reduce yellowing of the powder.

[0011] Document CN104910616 describes an elastomeric powder based on polyamide 12, containing a flexible segment synthesized from dodecanedioic acid, dual amine-terminated polyethylene glycol, and deuterated trifluoroacetic acid. The powder may further contain an antioxidant of phenolic, phosphite, or thioether type.

[0012] Document FR 3087198 describes a powder intended for 3D printing based on a thermoplastic polymer and containing at least 0.1% by weight of at least one thioether antioxidant relative to the total weight of the powder.

[0013] However, the antioxidant effects of the above compounds are not necessarily sufficient.

[0014] It is an object of the present invention to provide a solution to one or more of the above problems.

[0015] More particularly, it is an object of the present invention to provide a thermoplastic polymer powder, preferably a polyamide powder, which contains specific antioxidants and has improved thermal stability and also improved recyclability.

[0016] In the context of the present invention, a powder with improved thermal stability means a powder having a Yellowness Index (YI), measured after exposure to air for 72 hours in a volume of approximately 50 ml at 177° C., that is at least 30% lower than the index measured under the same conditions for the same powder without the particular antioxidant. Summary of the Invention

[0017] According to a first aspect, the present invention relates to a polymer powder suitable for 3D printing by sintering, comprising a thermoplastic polymer (a), preferably a polyamide, and an aliphatic sulfonate according to formula R-SO3X (b), or an aromatic sulfonate according to formula RY-SO3X (b), [In the formula, R represents a linear or branched, saturated or unsaturated aliphatic carbon-based chain having 4 to 30 carbon atoms, which may contain a group (in particular one group) selected from esters, amides, carboxylic acids, alcohols, nitriles, ketones and / or aldehydes, preferably selected from esters, amides, carboxylic acids and alcohols (in particular R can consist of a linear or branched, saturated or unsaturated aliphatic carbon-based chain having 4 to 30 carbon atoms), - Y represents one or more aromatic rings, - X represents a monovalent ion selected from the alkali metals, preferably a sodium ion, Concerning powders.

[0018] Typically, the sulfonate salt according to the present invention is aliphatic sulfonates containing a linear or branched saturated carbon-based chain having from 4 to 12 carbon atoms, preferably from 6 to 10 carbon atoms, such as sodium hexanesulfonate, sodium heptanesulfonate, sodium octanesulfonate, sodium nonanesulfonate, sodium decanesulfonate, sodium undecanesulfonate, sodium dodecanesulfonate; aliphatic sulfonates containing a linear or branched unsaturated carbon-based chain having from 4 to 30 carbon atoms, preferably from 12 to 18 carbon atoms, such as sodium olefin sulfonates having from 12 to 18 carbon atoms; and / or aliphatic or aromatic sulfonates containing a linear or branched, saturated or unsaturated carbon-based chain having from 4 to 30 carbon atoms, containing a group (especially one group) selected from esters, amides, acids, alcohols, nitriles and / or aldehydes, preferably selected from esters, amides, acids and alcohols; may be selected from:

[0019] The aliphatic sulfonates may contain, for example, a saturated or unsaturated carbon-based chain having from 4 to 30 carbon atoms, preferably having from 4 to 20 carbon atoms, containing an ester or amide group.

[0020] By way of example, mention may be made of the commercial products Hostapon® SCI 85 P and Hostapon® TPHC.

[0021] The aromatic sulfonate may be, for example, an alkylbenzenesulfonate, such as dodecylbenzenesulfonate, in which the benzene is substituted by at least one linear or branched, saturated or unsaturated carbon-based chain having from 4 to 18 carbon atoms.

[0022] Preferably, the sulfonate has a melting point below 300° C., preferably below 250° C. and more preferentially below 200° C., in particular below the melting point of the polymer powder.

[0023] The thermoplastic polymers used according to the present invention may be selected from polyolefins, polyamides, polyesters, polyaryletherketones, polyphenylene sulfides, polyacetals, polyimides, polyvinylidene fluorides, and / or mixtures thereof, preferably polyamides, polyaryletherketones, and / or mixtures thereof.

[0024] Preferably, the thermoplastic polymer according to the present invention is a semi-crystalline thermoplastic polymer.

[0025] According to one embodiment, the polymer powder further comprises a thioether, a filler or reinforcing material, and / or one or more further additives.

[0026] In the context of the present invention, it has been observed that the use of a sulfonate salt as defined above in a thermoplastic polymer powder, preferably a polyamide powder, makes it possible to improve the thermal stability of said powder while maintaining acceptable mechanical properties during successive builds.

[0027] More particularly, the addition of sulfonates makes it possible to very advantageously reduce the yellowing of the powder over successive builds.

[0028] Very advantageously, this improvement in heat stabilization was observed not only in the powder but also in the printing member.

[0029] Furthermore, it has been observed that the presence of sulfonates makes it possible to prevent a too great increase in the inherent viscosity of the non-agglomerated powder, thus enhancing the recyclability of the powder in the sintering process, and finally making it possible to obtain 3D components with effective mechanical properties.

[0030] The present invention therefore proposes powders that have excellent recyclability even when the sintering process is carried out under harsh conditions, typically in air at high temperatures (i.e. several tens of degrees below the melting point) and / or over long build times.

[0031] According to one embodiment, the polymer powder according to the invention comprises a thermoplastic polymer (a), a sulfonate (b) and optionally a thioether (c), a filler or reinforcing material (d), and / or one or more further additives (e).

[0032] According to one aspect, the present invention is directed to a method for preparing a powder as defined above.

[0033] Another subject of the invention is the use of sulfonates to improve the thermal stability, preferably to reduce yellowing, of thermoplastic polymer powders suitable for 3D printing by sintering.

[0034] According to one embodiment, the polymer powder further comprises a thioether.

[0035] The present invention also relates to a method of 3D printing, preferably a method of sintering induced by electromagnetic waves, using a powder as defined above or a powder comprising a non-agglomerated part of said powder recovered after one or more builds within the same or different printing method.

[0036] The electromagnetic radiation is preferably selected from a laser beam, infrared radiation, or UV radiation, with or without the use of absorbers.

[0037] The present invention also relates to an article obtainable by a 3D printing method as defined above.

[0038] The articles may be selected from prototypes, models, and parts, especially in the fields of automotive, marine, aviation, aerospace, medicine (prosthetics, hearing systems, tissues, etc.), textiles, clothing, fashion, decoration, design, electronics housings, telephony, computing, lighting, sports, and tools.

[0039] Preferably, the inherent viscosity of the printing member solution (also called "inherent viscosity") is greater than 0.8 so that the article has acceptable mechanical properties. More preferably, the inherent viscosity of the printing member is greater than 1.0. Generally, the inherent viscosity of the printing member is less than 4.0, and preferably less than 3.0.

[0040] The invention will now be described in detail and in a non-limiting manner in the following description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] definition In describing the invention, including the following examples, Dv50, also referred to herein as "volume median diameter", corresponds to the particle size value that exactly separates the population of particles being tested into two. Dv50 is measured according to standard ISO 13320-1. In the present description, a Malvern Insitec particle size analyzer with RTSizer software is used to obtain the particle size distribution of a powder and estimate its Dv50.

[0042] The inherent viscosity in a solution (in particular of a polyamide, a polyamide powder or a component produced by sintering from said polyamide or polyamide powder) is measured according to the following procedure: - taking a sample of polymer of between 0.07 and 0.10 g, preferably up to 0.15 g; - adding a sufficient amount of m-cresol solvent by weighing to obtain a concentration (C) of 0.5 g / l; - heating the mixture with stirring on a hot plate regulated at 100°C ± 5°C until the polymer is completely dissolved; - cooling the solution to room temperature, preferably over a period of at least 30 minutes; - measuring the flow time t0 of the pure solvent and the flow time t of the solution using a micro-Ubbelohde tube viscometer in a thermostatically controlled bath regulated at 20°C ± 0.05°C; - calculating the viscosity according to the formula 1 / C x Ln(t / t0), where C represents the concentration and Ln represents the natural logarithm.

[0043] For each sample, three measurements are carried out in different solutions and then the average is calculated.

[0044] The thermal properties of the polyamides are analyzed by DSC according to standard ISO 11357-3 "Plastics-Differential Scanning Calorimetry (DSC) Part 3: Determination of temperature and enthalpy of melting and crystallization". The temperatures more specifically relevant for the present invention herein are the melting point of the first heat (Mp1), the crystallization temperature (Tc) and the enthalpy of melting.

[0045] "Semicrystalline thermoplastic polymer" means - the crystallization temperature (Tc) determined in accordance with standard ISO 11357-3:2013 during a cooling step at a rate of 20 K / min in DSC (differential scanning calorimetry); - the melting point (Mp), determined in accordance with standard ISO 11357-3:2013 during a process of heating in a DSC at a rate of 20 K / min; - an enthalpy of fusion (ΔHf) determined in accordance with standard ISO 11357-3:2013 during a step of heating in a DSC at a rate of 20 K / min, which is greater than 5 J / g, preferably greater than 10 J / g, for example greater than 20 J / g, and generally less than 200 J / g, preferably less than 150 J / g, for example less than 100 J / g or less than 50 J / g; The term "thermoplastic polymer" refers to a thermoplastic polymer having the formula:

[0046] Yellowing is quantified by the Yellowness Index (YI), measured in accordance with standard ASTM E313-96 (D65), in particular using a Konica Minolta spectrocolorimeter with illuminant D65 at 10° in specularly included (SCI) mode.

[0047] The mechanical properties, in particular the tensile modulus and the elongation at break, are measured in accordance with standard ISO 527-1B:2012.

[0048] In describing the present invention, when referring to ranges, it is noted that expressions of the type "to" include the limits of the range.

[0049] Unless otherwise indicated, the percentages expressed are percent by weight. Unless otherwise indicated, the parameters mentioned are measured at atmospheric pressure and room temperature (23° C.).

[0050] The nomenclature used to designate polyamides follows standard ISO 1874-1:2011. The term "monomer" in the present description of polyamides should be taken to mean "repeating unit". In particular, in the designation PA "XY" designating a polyamide resulting from the condensation of a diamine with a dicarboxylic acid, X represents the number of carbon atoms of the diamine and Y represents the number of carbon atoms of the dicarboxylic acid. In the designation PA "Z", Z represents the number of carbon atoms of the polyamide unit resulting from the condensation of an amino acid or a lactam. Designations such as PA X / Y, PA X / Y / Z (also referred to as PA "X / Y" in the context of the present invention) relate to copolyamides, where X, Y, Z, etc. represent the homopolyamide units X, Y, Z as described in the present invention.

[0051] Thermoplastic Polymers Preferably, the thermoplastic polymer is a semi-crystalline thermoplastic polymer, preferably a polyamide.

[0052] The polyamides may be homopolyamides (i.e., PA "XY" and PA "Z"), copolyamides (i.e., PA "X / Y"), or mixtures thereof.

[0053] "Z"-type polyamides result from the condensation of one or more α,ω-aminocarboxylic acids and / or one or more lactams.

[0054] Examples of α,ω-aminocarboxylic acids include α,ω-amino acids such as aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, n-heptyl-11-aminoundecanoic acid, and 12-aminododecanoic acid.

[0055] Examples of lactams include those having 3 to 12 carbon atoms in the main ring, which may be substituted, such as β,β-dimethylpropiolactam, α,α-dimethylpropiolactam, amylolactam, caprolactam, capryllactam, enantholactam, 2-pyrrolidone, and lauryllactam.

[0056] Examples of preferred polyamides of this type include PA 6, PA 11 and PA 12.

[0057] "XY"-type polyamides result from the condensation of dicarboxylic acids with aliphatic, cycloaliphatic, or aromatic diamines.

[0058] Examples of diamines include aliphatic diamines having 6 to 12 atoms, where the diamine X can be aryl and / or saturated cyclic. Examples include hexamethylenediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, 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), metaxylylenediamine, trimethylhexamethylenediamine.

[0059] Examples of dicarboxylic acids include acids having 4 to 18 carbon atoms, preferably 9 to 12 carbon atoms, such as adipic acid, sebacic acid, azelaic acid, suberic acid, isophthalic acid, butanedioic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, the sodium or lithium salts of sulfoisophthalic acid, dimerized fatty acids (especially those having a dimer content of at least 98% and / or which are preferably hydrogenated), and 1,2-dodecanedioic acid HOOC-(CH2). 10 An example of such an alkyl group is --COOH.

[0060] Examples of preferred polyamides of this type are PA 612 resulting from the condensation of hexamethylenediamine and 1,12-dodecanedioic acid; PA 613 resulting from the condensation of hexamethylenediamine and brassylic acid; PA 912 resulting from the condensation of 1,9-nonanediamine and 1,12-dodecanedioic acid; PA 1010 resulting from the condensation of 1,10-decanediamine and sebacic acid; PA 1012 resulting from the condensation of 1,10-decanediamine and 1,12-dodecanedioic acid.

[0061] Polyamides are also the condensation of at least two different monomers, for example the condensation of at least two different α,ω-aminocarboxylic acids, or - Condensation of two different lactams, or - condensation of lactams and α,ω-aminocarboxylic acids with various carbon numbers, or - the condensation of at least one α,ω-aminocarboxylic acid (or lactam), at least one diamine and at least one dicarboxylic acid, or - condensation of an aliphatic diamine with an aliphatic dicarboxylic acid and at least one other monomer selected from aliphatic diamines other than those mentioned above and aliphatic dibasic acids other than those mentioned above It may also be a copolyamide resulting from

[0062] Mixtures of polyamides may also be utilized, such as mixtures of aliphatic and semi-aromatic polyamides, or mixtures of aliphatic and cycloaliphatic polyamides.

[0063] The polyamide of the invention may also be a copolymer having polyamide blocks and polyether blocks (PEBA) or a mixture of a copolymer having polyamide blocks and polyether blocks with at least one of the above polyamides.

[0064] PEBA copolymers are produced, for example, inter alia, from the copolycondensation of polyamide blocks having reactive ends and polyether blocks having reactive ends. 1) copolycondensation of polyamide blocks having diamine chain ends with polyoxyalkylene blocks having dicarboxylic acid chain ends; 2) copolycondensation of polyamide blocks having dicarboxylic acid chain ends with polyoxyalkylene blocks having diamine chain ends; 3) Copolycondensation of polyamide blocks having dicarboxylic acid chain ends with polyether diols (in this particular case the resulting product is a polyetheresteramide). It may arise from, etc.

[0065] The polyamide blocks may be homopolyamides or copolyamides as described above for homopolyamides and copolyamides.

[0066] Polyamide blocks with dicarboxylic acid chain ends result, for example, from the condensation of polyamide precursors in the presence of a chain limiter of the dicarboxylic acid type. Polyamide blocks with diamine chain ends result, for example, from the condensation of polyamide precursors in the presence of a chain limiter of the diamine type.

[0067] The polyether blocks of the PEBA may be derived from an alkylene glycol, such as PEG (polyethylene glycol), PPG (polypropylene glycol), PO3G (polytrimethylene glycol), or PTMG (polytetramethylene glycol), preferably PTMG.

[0068] Polymers having polyamide and polyether blocks may contain randomly distributed units. These polymers can be prepared by simultaneous reaction of the precursors of the polyether and polyamide blocks.

[0069] The polyether diol blocks are either used in unmodified form and copolycondensed with polyamide blocks having carboxylic acid end groups, or they are aminated to convert them to polyether diamines and condensed with polyamide blocks having carboxylic acid end groups. The polyether diol blocks can also be mixed with polyamide precursors and chain limiters to make polymers having polyamide blocks and polyether blocks with randomly distributed units.

[0070] The ratio of the amount of copolymer having polyamide blocks and polyether blocks to the amount of polyamide is advantageously between 1 / 99 and 15 / 85 by weight.

[0071] As regards the mixture of polyamide and at least one other polymer, it is provided in the form of a mixture with a polyamide matrix, the other polymer(s) forming the dispersed phase, examples of which may include polyolefins, polyesters, polycarbonates, PPO (abbreviation for polyphenylene oxide), PPS (abbreviation for polyphenylene sulfide) or elastomers.

[0072] Preferably, the powder composition is selected from polyamides, copolyamides, and / or PEBA copolymers comprising at least one of the following XY or Z monomers: 46, 4T, 54, 59, 510, 512, 513, 514, 516, 518, 536, 6, 64, 66, 69, 610, 612, 613, 614, 616, 618, 636, 6T, 9, 104, 109, 1010, 1012, 1013, 1014, 1016, 1018, 1036, 10T, 11, 12, 124, 129, 1210, 1212, 1213, 1214, 1216, 1218, 1236, 12T, MXD6, MXD10, MXD12, MXD14, and mixtures thereof; in particular PA 6, PA 11, PA 12, PA 612, PA 613, PA 912, PA 1010, PA1012 6, PA 6 / 12, PA 11 / 1010, and mixtures thereof.

[0073] Thioether The powder of the invention may advantageously comprise a thioether.

[0074] The thioether is preferably dilauryl thiodipropionate (DLTDP), ditridecyl thiodipropionate (DTDTDP), distearyl thiodipropionate (DSTDP), dimyristyl thiodipropionate (DMTDP), pentaerythrityl tetrakis (3-dodecyl thiopropionate or 3-lauryl thiopropionate), 3,3'-thiodipropionate, (C12-14) alkyl thiopropionate, dilauryl 3,3'-thiodipropionate. , ditridecyl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, dioctadecyl 3,3'-thiodipropionate, laurylstearyl 3,3-thiodipropionate, tetrakis[methylene 3-(dodecylthio)propionate]methane, thiobis(2-tert-butyl-5-methyl-4,1-phenylene)bis(3-(dodecylthio)propionate), 2,2'-thiodiethylenebis(3 -aminobutenoate), 4,6-bis(octylthiomethyl)-o-cresol, 2,2'-thiodiethylenebis3-(3,5-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-thiobis(4-methyl-6-tert-butylphenol), 2,2'-thiobis(6-tert-butyl-p-cresol), 4,4'-thiobis(6-tert-butyl-3-methylphenol), 4,4'-thiobis(4-methyl-6-tert-butylphenol), bi In some embodiments, the tert-butyl ester is selected from bis(4,6-tert-butyl-1-yl-2-)sulfide, tridecyl-3,5-di-tert-butyl-4-hydroxybenzylthioacetate, 1,4-bis(octylthiomethyl)-6-phenol, 2,4-bis(dodecylthiomethyl)-6-methylphenol, distearyl disulfide, bis(methyl-4-3-n-(C12 / C14)alkylthiopropionyloxy-5-tert-butylphenyl)sulfide, and / or mixtures thereof.

[0075] More preferably, the thioether according to the present invention is selected from the group consisting of dilauryl thiodipropionate (DLTDP), ditridecyl thiodipropionate (DTDTDP), distearyl thiodipropionate (DSTDP), dimyristyl thiodipropionate (DMTDP), pentaerythrityl tetrakis (3-dodecylthiopropionate or 3-laurylthiopropionate), and / or mixtures thereof.

[0076] Even more preferably, the thioether is DLTDP.

[0077] Even more preferably, the thioether is pentaerythrityl tetrakis(3-dodecylthiopropionate). Such a compound is sold in particular by the company Songnox or by the company Adeka under the trade name ADK STAB AO-412S.

[0078] Preferably, the thioether has a melting point of less than or equal to 180°C, preferably less than or equal to 160°C, preferentially less than or equal to 140°C, even more preferentially less than or equal to 130°C, or less than or equal to 100°C.

[0079] Polymer Powder According to one embodiment, the polymer powder according to the invention comprises a thermoplastic polymer (a), a sulfonate (b), and optionally a thioether (c), a filler or reinforcing material (d), and / or one or more further additives (e).

[0080] According to one embodiment, the powder according to the invention comprises: (a) 30% to 99.9%, preferably 40% to 95%, by weight of a thermoplastic polymer as defined above; (b) 0.1% to 10%, preferably 0.1% to 5%, by weight of a sulfonate salt as defined above; (c) 0% to 5%, preferably 0.1% to 1%, by weight of a thioether as defined above; (d) 0% to 50%, preferably 10% to 50%, in particular 20% to 40%, by weight of a filler or reinforcing material; and (e) 0% to 10%, preferably 0.1% to 7.5%, in particular 1% to 5% by weight of further additives wherein the percentages of components (a), (b), (c), (d), and (e) total 100%.

[0081] According to one embodiment, the powder according to the invention comprises: (a) 75% to 99.9%, preferably 85% to 99%, by weight of a thermoplastic polymer as defined above; (b) 0.1% to 10%, preferably 0.1% to 5%, by weight of a sulfonate salt as defined above; (c) 0% to 5%, preferably 0.1% to 1%, by weight of a thioether as defined above; (e) 0% to 10%, preferably 0.1% to 7.5%, in particular 1% to 5% by weight of further additives wherein the percentages of components (a), (b), (c), and (e) total 100%.

[0082] Component (e) may contain one or more of these additives.

[0083] According to one embodiment, the sulfonate represents 0.1% to 3%, or 3% to 5%, or 5% to 10%, or 10% to 15%, or 15% to 20% by weight relative to the total weight of the polymer powder. In particular, the sulfonate may represent 0.5% to 10% by weight, or 0.5% to 5% by weight relative to the total weight of the polymer powder.

[0084] Preferably, the thioether represents at least 0.1% by weight relative to the total weight of the polymer powder, preferably between 0.1% and 5%, preferably between 0.1% and 3%, preferably between 0.1% and 2%, preferably between 0.1% and 1%.

[0085] Typically, the thioether represents at least 0.2% by weight relative to the total weight of the polymer powder, such as at least 0.3%, typically at least 0.4%, and typically less than 5%, such as less than 4%, preferably less than 3%.

[0086] Preferably, the polymer powder has a first heat melting point (Mp1) of 80 to 220°C, preferably 100 to 200°C.

[0087] The powder may have a crystallization temperature (Tc) of 40 to 250°C, preferably 45 to 200°C, for example 45 to 150°C.

[0088] When considering a mixture of polymers (a), the lowest Mp in the mixture is considered to be the Mp and the highest Tc in the mixture is considered to be the Tc.

[0089] The difference between the Tc and Mp of the powder is preferably 20°C or more, or more preferably even 30°C or more.

[0090] According to one embodiment, the powder has an inherent viscosity in solution of typically less than 3, preferably less than 2, prior to use in the sintering process.

[0091] Preferably, the inherent viscosity of the powder not affected by electromagnetic waves after the first build in the sintering process is 0.8-3, preferably 1-2.

[0092] Typically, the polymer powder according to the invention has a Dv50 diameter of 40 to 150 μm, preferably 40 to 100 μm. For example, the Dv50 diameter of the polymer powder may be 40-45 μm; or 45-50 μm; or 50-55 μm; or 55-60 μm; or 60-65 μm; or 65-70 μm; or 70-75 μm; or 75-80 μm; or 80-85 μm; or 85-90 μm; or 90-95 μm; or 95-100 μm; or 100-105 μm; or 105-110 μm; or 110-115 μm; or 115-120 μm; or 120-125 μm; or 125-130 μm; or 130-135 μm; or 135-140 μm; or 140-145 μm; or 145-150 μm.

[0093] Fillers and Reinforcements The polymer powder according to the invention may further comprise fillers or reinforcing materials, in particular to ensure that the printed article has sufficient mechanical properties, in particular with regard to the modulus of elasticity. These fillers may in particular be carbonate minerals, in particular calcium carbonate, magnesium carbonate, dolomitic limestone, calcite, barium sulfate, calcium sulfate, dolomitic minerals, alumina hydrate, wollastonite, montmorillonite, zeolite, perlite, or nanofillers (fillers with dimensions of the order of nanometers), such as nanoclays, calcium silicates, magnesium silicates, such as talcum, mica, kaolin, attapulgite, and mixtures thereof. As reinforcing materials, mention may in particular be made of carbon nanotubes, glass powders, glass fibers and carbon fibers, and also solid or hollow glass beads, optionally coated with silane. Component (c) may comprise one or more fillers and / or reinforcing materials. Advantageously, the fillers and reinforcing materials do not comprise pigments, as defined below for the pigment composition.

[0094] More specifically, the powder of the invention may comprise 0% to 60%, or 5% to 50%, or 10% to 40%, or 10% to 30% by weight of component (c). According to one embodiment, the polymer powder is free of fillers and reinforcing agents.

[0095] Further Additives The polymer powder may, if desired, comprise further additives that are customary in polymer powders used in 3D printing by sintering.

[0096] These may in particular be additives that contribute to improving the behavior of the powders in 3D printing by sintering, whether in powder form or not, as well as additives that make it possible to improve the properties of the printed articles, in particular their mechanical strength, heat resistance, fire resistance, in particular their elongation at break and their impact strength.

[0097] These customary additives may in particular be chosen from flow agents, chain limiters, fire retardants, flame retardants, UV stabilizers, antioxidants, antiwear agents, light stabilizers, impact modifiers, antistatic agents, pigments, and waxes.

[0098] Flow Agent By way of example, the flow agent may be selected from silica, in particular hydrophobic fumed silica; for example, the product sold under the name Cab-o-Sil® TS610 by Cabot Corporation, precipitated silica, hydrous silica, quartz glass, pyrogenic silica, vitreous oxides, in particular vitreous phosphates, vitreous borates, alumina, for example amorphous alumina, and mixtures thereof.

[0099] Antioxidants For example, the powders of the invention may contain phenolic antioxidants, such as 3,3'-bis(3,5-di-tert-butyl-4-hydroxyphenyl)-N,N'-hexamethylenedipropionamide, in particular that sold under the name Palmarole AO.OH.98 by Palmarole, (4,4'-butylidenebis(2-t-butyl-5-methylphenol), in particular that sold under the name Lowinox® 44B25 by Addivant, pentaerythrityl tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), in particular that sold under the name Irganox® 1010 by BASF, N,N'-hexane-1, 6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide)), in particular that sold under the name Irganox® 1098 by BASF, 3,3',3',5,5',5'-hexa-tert-butyl-a,a',a'-(mesitylene-2,4,6-triyl)tri-p-cresol, in particular that sold under the name Irganox® 1330 by BASF, ethylenebis(oxyethylene N'N'-(2-ethyl-2-methyl-4-phenylene)bis(3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate), in particular that sold under the name Irganox® 245 by BASF, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, in particular that sold under the name Irganox® 3114 by BASF, [(4,4',4''-trimethyl-1,3,5-benzenetriyl)tris(methylene)]tris2,6-bis(1,1-dimethylethyl)phenol, in particular that sold under the name Alvinox® 1330 by the company 3V, Hostanox® 245 FF, Hostanox® 245 Pwd by the company Clariant, pentaerythrityl tetrakis(3-(3,octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), in particular that sold under the name Evernox® 10 and Evernox® 10GF by Everspring Chemical Company Limited; octadecyl 3-(3,5-di-tert-4-hydroxyphenyl)propionate, in particular that sold under the name Evernox® 76 and Evernox® 76GF by Everspring Chemical Company Limited; tetrakis[methylene-3-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate]methane, in particular that sold under the name BNX® 1010 by Mayzo; thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], in particular that sold under the name BNX® 1035 by Mayzo; -3-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate]methane, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, in particular that sold by Mayzo under the name BNX (registered trademark) 2086, and 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)trione, in particular that sold by Mayzo under the name BNX (registered trademark) 3114.

[0100] The powder may also contain antioxidants, such as compounds containing aromatic or aliphatic phosphonites (such as the product Hostanox® P-EPQ® sold by Clariant), alkali metal salts of phenylphosphonic acid or hypophosphorous acid, compounds containing phosphite functional groups, such as trialkyl phosphites and trialkylaryl phosphites, as well as cyclic diphosphites derived from pentaerythritol. Mention may be made of Irgafos® 168 sold by BASF. Examples of trialkyl and trialkylaryl phosphites include trinonyl phosphite, tri(nonylphenyl) phosphite, and tri[(2,4-di-tert-butyl-5-methyl)phenyl] phosphite. An example of a cyclic diphosphite derived from pentaerythritol may include distearyl pentaerythritol diphosphite.

[0101] Pigments The pigment may be a pigment having an absorbance of less than 40% for light having a wavelength of 1000 nm, measured according to standard ASTM E1790, such as one selected from metal oxides and transition metal oxides, and also their corresponding mixtures, mixed oxides, and doped oxides. For example, the oxide is selected from titanium oxide, tin oxide, magnesium oxide, copper oxide, zinc oxide, iron oxide, manganese oxide, cobalt oxide, nickel oxide, aluminum oxide, antimony oxide, chromium oxide, titanium oxide, or silicon oxide, or their corresponding mixtures, mixed oxides, or doped oxides.

[0102] wax The waxes may include polyethylene and polypropylene, polytetrafluoroethylene, ketone, acid, partially esterified acid, anhydride, ester, aldehyde, amide waxes, derivatives and mixtures thereof. The waxes may in particular include the products sold under the names Crayvallac® WN1135, WN1495 or WN1265 by the company Arkema or Ceridust® 9615A or 8020 by the company Clariant.

[0103] According to one embodiment, the wax is present in the composition in the form of a coating that at least partially covers the polymer powder.

[0104] Chain Limiting Agent The powders of the present invention may include a chain limiting agent selected from dicarboxylic acids, monocarboxylic acids, diamines and monoamines, each of which may be linear or cyclic.

[0105] Preferably the chain limiter has a melting point below 180°C.

[0106] The monocarboxylic acid preferably has 2 to 20 carbon atoms. Examples of monocarboxylic acids include acetic acid, propionic acid, benzoic acid, and stearic acid, lauric acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, hexadecanoic acid, octodecanoic acid, and tetradecanoic acid.

[0107] The dicarboxylic acid preferably has 2 to 20 carbon atoms, more preferably 6 to 10. Examples of the dicarboxylic acid include sebacic acid, adipic acid, azelaic acid, suberic acid, dodecanedicarboxylic acid, butanedioic acid, and orthophthalic acid.

[0108] The monoamine may in particular be a primary amine having from 2 to 18 carbon atoms. Examples of monoamines include 1-aminopentane, 1-aminohexane, 1-aminoheptane, 1-aminooctane, 1-aminononane, 1-aminodecane, 1-aminoundecane, 1-aminododecane, benzylamine, and oleylamine.

[0109] The diamine may in particular be a primary diamine containing 4 to 20 carbon atoms. Examples of diamines include the isomers of bis(4-aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), and 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), as well as para-aminodicyclohexylmethane (PACM), isophoronediamine (IPDA), 2,6-bis(aminomethyl)norbornane (BAMN), and piperazine.

[0110] According to one embodiment, the chain limiting agent represents from 0.01% to 10%, preferably from 0.01% to 5%, preferably from 0.01% to 4%, preferably from 0.01% to 3%, preferably from 0.01% to 2%, preferably from 0.01% to 1% by weight relative to the total weight of the thermoplastic polymer or, if the thermoplastic polymer is a polyamide, relative to the total weight of the polyamide.

[0111] The chain limiting agent may represent from 0.01% to 2% by weight, based on the total weight of the thermoplastic polymer, or, if the thermoplastic polymer is a polyamide, based on the total weight of the polyamide.

[0112] Preferably, the chain limiting agent represents 0.01% to 0.5%, 0.01% to 0.4%, 0.01% to 0.3%, 0.01% to 0.2% by weight based on the total weight of the thermoplastic polymer, or based on the total weight of the polyamide if the thermoplastic polymer is a polyamide.

[0113] Method for preparing polymer powder The polymer powder can be prepared according to conventional methods.

[0114] Commercially available thermoplastic polymers (component (a)), especially in the form of granules, flakes or powder, may be used. If necessary, component (a) can be converted into a powder by known methods, especially by grinding.

[0115] The grinding may be a room temperature grinding.

[0116] Alternatively, grinding may be cryogenic grinding, in which the material to be ground is cooled, for example with liquid nitrogen, liquid carbon dioxide, or liquid helium, to make the material more brittle and therefore easier to grind.

[0117] Grinding can be carried out, for example, in a pin mill, a hammer mill, or a whirl mill.

[0118] In this case, the method for preparing the powder according to the invention comprises: (i) grinding the thermoplastic polymer (a) to obtain a powder having a Dv50 diameter of 40 to 150 μm, and thereafter or before (ii) introducing at least one sulfonate (b) as defined above, and optionally also one or more of the components (c) to (e); Includes.

[0119] The components may be added to the thermoplastic polymer (component (a)) prior to grinding according to methods known to those skilled in the art.

[0120] By way of example, the addition can be carried out in the melt, for example in an extruder (compounding), or by wet impregnation (see, for example, the method described in EP 3325535 B1).

[0121] If the components are added after grinding, for example by dry mixing, it is preferred that the components are in a powdered form with a Dv suitable for 3D printing.

[0122] Alternatively, the sulfonate (component (b)), and optionally one or more of components (c)-(e), may be added to the thermoplastic polymer during its synthesis.

[0123] In this case, the method for preparing the powder according to the invention comprises: (i) synthesizing a thermoplastic polymer (a), during or before the step of: (ii) introducing at least one sulfonate (b) as defined above, and optionally also one or more of the components (c) to (e); Includes.

[0124] For example, it is possible to mix the components by co-precipitating the polymer from a solution in the presence of the additive component(s) (dissolution / precipitation). The conditions can be easily adapted by a person skilled in the art. Reference may be made, for example, to document EP 0863174 B1.

[0125] It is also possible to mix the component with the prepolymer of component (a) during or after the synthesis of the prepolymer in the method described in U.S. Pat. No. 9,738,756, or to mix the component with the prepolymer in the melt phase (compounding), as described in EP 2 247 646 B1.

[0126] Alternatively or additionally, the sulfonate (component (b)), and optionally one or more other components, may be added by dry mixing with the thermoplastic polymer (a).

[0127] In this case, the process for preparing the powder according to the invention comprises a step in which the sulfonate (b) and, optionally, one or more of the components (c) to (e) are incorporated into the powder by dry mixing.

[0128] Depending on the additive, it is possible to use several of these methods in introducing the additive into the polymer composition.

[0129] The powder thus obtained may then be sieved or subjected to a screening step in order to obtain the desired particle size profile.

[0130] In order to make the polymer powder more suitable for 3D printing by sintering, the polymer powder may then be subjected to various treatments, in particular thermal or hydrostatic treatments, as required, before use.

[0131] Depending on the preparation method, the components can be used in any suitable form.

[0132] According to one embodiment, one or more components are used in powder form. The shape and size of the particles forming the powder are not particularly limited, except for the application of 3D printing by sintering. The particles generally have a spherical shape. However, their use in other shapes, such as rod-shaped or lamellar shapes, is not excluded.

[0133] When the components are added to a dry mixed polymer, they advantageously have a volume median diameter Dv50 approximately equal to or less than the volume median diameter of the powders they are mixed with. More specifically, the volume median diameter Dv50 of the components is preferably 0.01 to 50 μm, preferably 0.05 to 30 μm, more preferably 0.1 to 20 μm, especially 0.2 to 10 μm, and most specifically 0.5 to 5 μm.

[0134] The invention will now be further illustrated, without being limited thereto, by the following examples. EXAMPLES

[0135] The following examples illustrate the invention without limiting its scope, in which all percentages and parts are expressed by weight, unless otherwise specified.

[0136] Although the tests focus on a powder composition based on polyamide 11, it is understood that the composition according to the invention is not limited to this embodiment and may comprise any type of polymer, in particular polyamide, either alone or in a mixture.

[0137] Example I The base powder 1 used is a powder containing, relative to the total weight of base powder 1, 99.2 wt. % of polyamide 11; 0.6 wt. % of the antioxidant N,N'-1,6-hexanediylbis[3-(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropanamide)]; and 0.2 wt. % of a flow agent (hydrophobic fumed silica).

[0138] Polyamide 11 was prepared according to the method described in EP 2247646 B1, where antioxidants were incorporated into the polyamide prepolymer by compounding.

[0139] Flow agents were then added by dry mixing as follows:

[0140] The compounds to be mixed are introduced into a Henschel IAM 6L mixer in the proportions indicated above and stirring is carried out at room temperature and at 900 rpm for 100 seconds.

[0141] The measured Dv50 of the powder is 50 μm.

[0142] In Examples 2-3, the sulfonate is added to the polymer powder by dry mixing as follows.

[0143] The polyamide powder is introduced into a Henschel IAM 6L mixer together with the sulfonate salts in the proportions indicated in Table 1 below and stirring is carried out at room temperature at 900 rpm for 100 seconds. TIFF2024525451000001.tif52170

[0144] Hostapon® TPHC is a product sold by Clariant, sodium 2-(methyloleoylamino)ethane-1-sulfonate.

[0145] Hostapon® SCI 85 is a product sold by Clariant, 2-butanoyloxyethanesulfonate (also called sodium cocoyl isethionate).

[0146] Aging test of powder and measurement of yellowness index (YI) a) Solid State The test consisted of exposing the example powders in glass jars placed in a ventilated oven for 72 hours at 177° C. The results are shown in Table 2.

[0147] This test simulates the exposure conditions that powders may be exposed to in a 3D printer. The Yellowness Index (YI) measurement is performed with a Konica Minolta spectrophotometer with illuminant D65 at 10° in specular reflection included (SCI) mode according to standard ASTM (E313-96) (D65).

[0148] b) Molten state The test consists of exposing the example powders in aluminium crucibles placed in a ventilated oven for 2 hours at 220° C. (powder layer approximately 2 mm thick).

[0149] The molten film is then removed and a measurement is taken by placing it in front of the white portion of a Leneta form 2A opacity chart.

[0150] This test simulates the exposure conditions that a part may be exposed to in a 3D printer as it is built.

[0151] The yellowness index (YI) measurements are performed with a Konica Minolta spectrophotometer with illuminant D65 at 10° in SCI mode according to standard ASTM (E313-96) (D65). The results are shown in Table 2. TIFF2024525451000002.tif69170

[0152] During aging tests in the solid and molten state, lower Yellowness Index values ​​were observed for the powders containing sulfonate (Examples 2 and 3) compared to the powder without sulfonate (Example 1). The use of sulfonate in the polyamide powder therefore makes it possible to improve the color stability of the powder and also of the printing member.

[0153] Example II The base powders 2 and 3 used contain, relative to the total weight of the base powder, 98.9 wt. % polyamide 11; 0.4 wt. % antioxidant triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate; 0.2 wt. % flow agent (hydrophobic fumed silica), and 0.5 wt. % thioether.

[0154] The measured Dv50 of the powder is 50 μm.

[0155] The thioether used in Base Powder 2 is pentaerythrityl tetrakis(3-dodecylthiopropionate) sold by Adeka.

[0156] The thioether used in Base Powder 3 is dilauryl thiodipropionate (DLTDP) sold by Songnox.

[0157] Base powders 2 and 3 were prepared according to the method described in EP 2247646 B1, where the antioxidant and thioether were added to the polymer by compounding. Flow agents were then added to the powders by dry mixing according to the method described in Example I.

[0158] In Examples 6-9, additional sulfonate salt is added to the base powder by dry mixing according to the method described in Example I. TIFF2024525451000003.tif65170

[0159] Aging test of powder and measurement of yellowness index (YI) Aging tests in the solid and molten state were carried out according to the protocol described in Example I. TIFF2024525451000004.tif88170

[0160] During aging tests in the solid and molten state, lower yellowness index values ​​were observed for the powders containing sulfonate (Examples 6 to 9) compared to the powders not containing sulfonate (Examples 4 to 5). The use of sulfonate in polyamide powders containing thioethers therefore makes it possible to very advantageously improve the color stability of the powder and also of the printing member.

[0161] Inherent Viscosity of Powders The inherent viscosity is measured at 20° C. in a 0.5% by weight solution in meta-cresol according to standard ISO 307:2007.

[0162] Example 9 in Table 5 (containing sulfonate) shows less increase in inherent viscosity than Examples 4 and 5 (without sulfonate), indicating that the addition of sulfonate to the powder stabilizes the inherent viscosity of the powder and also allows the powder to be better recycled since it is less reactive. TIFF2024525451000005.tif44170

Claims

1. A polymer powder suitable for 3D printing by sintering, comprising a thermoplastic polymer (a), preferably a polyamide, and an aliphatic sulfonate (b) of the formula R-SO ３ X, or an aromatic sulfonate (b) of the formula R-Y-SO ３ X [wherein, - R represents a linear or branched, saturated or unsaturated aliphatic carbon chain having 4 to 30 carbon atoms, optionally containing a group selected from ester, amide, carboxylic acid, alcohol, nitrile, ketone, and / or aldehyde, preferably selected from ester, amide, carboxylic acid, and alcohol; - Y represents one or more aromatic rings; - X represents a monovalent ion selected from alkali metals, preferably sodium ion] comprising a powder.

2. The sulfonate is - an aliphatic sulfonate containing a linear or branched saturated carbon chain having 4 to 12 carbon atoms, preferably 6 to 10 carbon atoms, such as sodium hexanesulfonate, sodium heptanesulfonate, sodium octanesulfonate, sodium nonanesulfonate, sodium decanesulfonate, sodium undecanesulfonate, sodium dodecanesulfonate; - an aliphatic sulfonate containing a linear or branched unsaturated carbon chain having 4 to 30 carbon atoms, preferably 12 to 18 carbon atoms, such as sodium olefinsulfonate having 12 to 18 carbon atoms; and / or - an aliphatic or aromatic sulfonate containing a linear or branched, saturated or unsaturated carbon chain having 4 to 30 carbon atoms, preferably selected from ester, amide, acid, alcohol, nitrile, and / or aldehyde, preferably selected from ester, amide, acid, and alcohol selected from, the powder according to Claim 1.

3. The powder according to Claim 1, wherein the thermoplastic polymer is a semi-crystalline thermoplastic polymer, preferably polyamide.

4. The powder according to Claim 1, further comprising a thioether, a filler or a reinforcing material, and / or one or more additional additives.

5. (a) 30% to 99.9% by weight, preferably 40% to 95% by weight of a thermoplastic polymer; (b) 0.1% to 10% by weight, preferably 0.1% to 5% by weight of a sulfonate; (c) 0% to 5% by weight, preferably 0.1% to 1% by weight of a thioether; (d) 0% to 50% by weight, preferably 10% to 50% by weight, particularly 20% to 40% by weight of a filler or a reinforcing material; and (e) 0% to 10% by weight, preferably 0.1% to 7.5% by weight, particularly 1% to 5% by weight of an additional additive The powder according to claim 1, comprising and having the proportions of components (a), (b), (c), (d), and (e) totaling 100%.

6. (a) 75% to 99.9% by weight, preferably 85% to 99% by weight, of a thermoplastic polymer; (b) 0.1% to 10% by weight, preferably 0.1% to 5% by weight, of a sulfonate; (c) 0% to 5% by weight, preferably 0.1% to 1% by weight, of a thioether; (e) 0% to 10% by weight, preferably 0.1% to 7.5% by weight, particularly 1% to 5% by weight, of a further additive The powder according to claim 1, comprising and having the proportions of components (a), (b), (c), and (e) totaling 100%.

7. The powder according to any one of claims 4 to 6, wherein the thioether is selected from dilauryl thiodipropionate (DLTDP), ditridecyl thiodipropionate (DTDTDP), distearyl thiodipropionate (DSTDP), dimyristyl thiodipropionate (DMTDP), pentaerythrityl tetrakis(3-dodecylthiopropionate or 3-laurylthiopropionate), and / or mixtures thereof.

8. The powder according to claim 1, having a Dv50 diameter of 40 to 150 μm.

9. (i) A step of grinding a thermoplastic polymer to obtain a powder having a Dv50 diameter of 40 to 150 μm, and then or before that, (ii) A step of introducing at least one sulfonate and also, optionally, one or more components A method for preparing the powder according to claim 1, comprising.

10. (i) A step of synthesizing a thermoplastic polymer (a), and during or before that, (ii) A step of introducing at least one sulfonate (b) as defined above and also, optionally, one or more components (c) to (e) A method for preparing the powder according to claim 1, comprising.

11. A method for preparing the powder according to claim 1, comprising a step of incorporating the sulfonate (b) and, optionally, one or more components (c) to (e) into the powder by dry mixing.

12. Use of the sulfonate according to claim 1 for improving the thermal stability of a polymer powder suitable for 3D printing by sintering, particularly for suppressing yellowing.

13. The use according to claim 12, wherein the powder comprises a thioether selected from dilauryl thiodipropionate (DLTDP), ditridecyl thiodipropionate (DTDTDP), distearyl thiodipropionate (DSTDP), dimyristyl thiodipropionate (DMTDP), pentaerythrityl tetrakis(3-dodecylthiopropionate or 3-laurylthiopropionate), and / or mixtures thereof.

14. A 3D printing method, preferably a method of sintering induced by electromagnetic waves, using the powder according to claim 1 or a powder composition comprising a non-agglomerated portion of the powder according to claim 1 recovered after one or more builds within the same printing method or different printing methods.

15. A manufactured article obtained by the 3D printing method according to claim 14.