Thermoplastic polymer powders for 3D printing

Abstract

The present invention relates to polymer powders for producing articles, particularly by 3D printing by sintering, comprising a thermoplastic polymer, an antioxidant, and specific metal oxides, metal hydroxides, and / or hydrotalcites, with improved thermal stability, improved recyclability, and improved consistency of mechanical properties of the sintered parts. 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 for producing articles, in particular by 3D printing by sintering, comprising a thermoplastic polymer, an antioxidant, and specific compounds selected from metal oxides, metal hydroxides, and / or hydrotalcites, and having improved thermal stability, improved recyclability, and improved consistency of mechanical properties of the sintered parts.

[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 powders. 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 one or more laser beams (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, the presence of oxygen at high temperatures during the sintering process can cause thermo-oxidative degradation of the polymer, including undesirable yellowing of the powder, thereby preventing reuse of the non-agglomerated powder. A decrease in the inherent viscosity of the powder due to thermo-oxidative degradation of the powder can also be observed; the resulting sintered parts can have poor mechanical properties. These thermo-oxidative phenomena can also occur in equipment with an inert environment, where the oxygen content is steadily reduced but oxygen is still present.

[0008] There is a continuing need to provide thermoplastic polymer powders with good thermal stability in order to produce sintered parts with sufficient mechanical properties and that are recyclable.

[0009] For the purposes of the present invention, thermal stability is understood to mean a reduced thermo-oxidative degradation, i.e. in particular a reduced yellowing of non-agglomerated powders during sintering (i.e. a reduced increase in YI) and / or a limited reduction in the inherent viscosity.

[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 FR 3087198 describes a powder intended for 3D printing, based on a thermoplastic polymer and containing a thioether antioxidant.

[0012] However, the antioxidant effect of thioethers has not always been found to be sufficient. In fact, when thioethers are used in a 3D printer, yellowing of the powder has been observed. Furthermore, an unpleasant sulfur odor is felt during use and even after conversion in the 3D printer.

[0013] US 2004 / 0138363 describes a powder containing polyamide and titanium oxide particles, which is shown to be resistant to yellowing when the powder is subjected to thermal stress during 3D printing by laser sintering.

[0014] However, it is not necessarily known that titanium oxide has a sufficient anti-yellowing effect.

[0015] It is an object of the present invention to provide a solution to one or more of the above problems.

[0016] More specifically, it is an object of the present invention to provide thermoplastic polymer powders, preferably polyamide powders, comprising antioxidants and specific metal oxides, metal hydroxides and / or hydrotalcites, which have improved thermal stability and thus better recyclability.

[0017] 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 20% lower than the index measured under the same conditions for the same powder in the absence of the particular metal oxide, metal hydroxide, and / or hydrotalcite. Summary of the Invention

[0018] According to a first aspect, the present invention relates to a polymer powder suitable for 3D printing by sintering, the powder comprising: (a) a semi-crystalline thermoplastic polymer; (b) one or more antioxidants; and (c) a metal oxide, metal hydroxide, and / or hydrotalcite derived from one or more alkaline earth metals, or one or more post-transition metals, preferably one or more post-transition metals.

[0019] The semi-crystalline thermoplastic polymers used according to the invention may be selected from polyolefins, polyamides, polyesters, polyaryletherketones, polyphenylene sulfides, polyacetals, polyimides, polyvinylidene fluorides, and / or mixtures thereof, preferably polyamides.

[0020] According to one embodiment, the metal oxide is selected from ZnO and / or Al2O3.

[0021] It is preferred that component (c) is in powder form with a Dv suitable for 3D printing.

[0022] According to one embodiment, the one or more antioxidants are selected from one or more phenolic antioxidants, one or more phosphite / phosphonite antioxidants, one or more thioethers, and / or mixtures thereof.

[0023] Thus, the powders of the invention may comprise mixtures of phenolic and phosphite / phosphonite antioxidants, or mixtures of phenolic and thioether antioxidants, or mixtures of phosphite / phosphonite and thioether antioxidants, or mixtures of phenolic and phosphite / phosphonite and thioether antioxidants.

[0024] Preferably, the one or more antioxidants are selected from one or more phenolic antioxidants, one or more thioethers, and / or mixtures thereof.

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

[0026] In the context of the present invention, it has been observed that the use of certain metal oxides, metal hydroxides and / or hydrotalcites, preferably in combination with one or more antioxidants, in thermoplastic polymer powders suitable for 3D printing by sintering makes it possible to improve the thermal stability of said powders while maintaining acceptable mechanical properties during successive builds.

[0027] More particularly, the addition of metal oxides, metal hydroxides and / or hydrotalcites as defined in the present invention, preferably in combination with one or more antioxidants, in polymer powders suitable for printing by sintering makes it possible to suppress yellowing of the powder during successive builds and / or for printing members in a highly advantageous manner.

[0028] Additionally, a reduction in the unpleasant sulfur odor was observed during use and even after conversion in the 3D printer.

[0029] The present invention therefore proposes powders that have excellent recyclability, even when the sintering process is carried out under harsh conditions, typically under air at high temperatures (i.e. generally a few degrees below the melting point) and / or over long build times and / or when large volume components are produced.

[0030] Moreover, it has been surprisingly observed that the addition of metal oxides, metal hydroxides and / or hydrotalcites as defined in the present invention, preferably in combination with one or more antioxidants, makes it possible to obtain printing elements with improved mechanical properties throughout the entire production, while avoiding the production of elements with low elongation at break (generally less than 10%).In fact, compared to the very same powders without the addition of metal oxides, metal hydroxides and / or hydrotalcites as defined in the present invention, elements with low elongation are generally observed, which may result in large quantities of elements with properties that are not sufficient for industrial-scale production.

[0031] According to one aspect, the present invention is directed to a method for preparing a powder as defined above.

[0032] The subject of the present invention is also the use of metal oxides, metal hydroxides and / or hydrotalcites derived from one or more alkaline earth metals or one or more post-transition metals, preferably one or more post-transition metals, in a polymer powder suitable for 3D printing by sintering, to improve the thermal stability of said powder, in particular to reduce yellowing.

[0033] The subject of the present invention is also the use, in a polymer powder suitable for 3D printing by sintering, of metal oxides, metal hydroxides and / or hydrotalcites derived from one or more alkaline earth metals or one or more post-transition metals, preferably one or more post-transition metals, to improve the mechanical properties, in particular the elongation at break, of the printed members produced from said powder.

[0034] Preferably, the powder comprises one or more antioxidants, preferably selected from one or more phenolic antioxidants, one or more phosphite / phosphonite antioxidants, one or more thioethers, and / or mixtures thereof.

[0035] Preferably, the metal oxide is selected from ZnO and / or Al2O3.

[0036] The invention also relates to a 3D printing method, preferably by electromagnetic wave induced sintering, 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.

[0037] The electromagnetic radiation is preferably selected from one or more laser beams, infrared radiation, or UV radiation, with or without the use of absorbers.

[0038] The present invention also relates to an article obtainable by a 3D printing method as defined above.

[0039] 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.

[0040] 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.

[0041] The invention will now be described in detail and in a non-limiting manner in the following description. [Brief description of the drawings]

[0042] [Figure 1] FIG. 3D printed model of the test specimen along the z-axis. [Diagram 2] 1 shows the percentage of specimens with elongation greater than x%, where x is the abscissa of the graph. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] 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.

[0044] 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 ambient 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.

[0045] For each sample, three measurements are carried out in different solutions and then the average is calculated.

[0046] 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.

[0047] "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, for example greater than 10 J / g, preferably greater than 20 J / g, generally less than 205 J / g, preferably less than 150 J / g; The term "thermoplastic polymer" refers to a thermoplastic polymer having the formula:

[0048] Yellowing is quantified by the Yellowness Index (YI), measured in accordance with standard ASTM E313-96 (D65) using a Konica Minolta spectrocolorimeter with illuminant D65 at 10° in reflectance mode with specular reflection included (SCI).

[0049] The mechanical properties, in particular the tensile modulus and the elongation at break, are measured in accordance with standard ISO 527-1B:2012.

[0050] In describing the present invention, when referring to ranges, it is noted that expressions of the type "to" include the limits of the range.

[0051] Unless otherwise indicated, the percentages expressed are percentages by weight. Unless otherwise indicated, the parameters mentioned are measured at atmospheric pressure and ambient temperature (23° C.).

[0052] The nomenclature used to designate polyamides follows standard ISO 1874-1:2011. In the present description, the term "monomer" 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 called 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.

[0053] Semicrystalline Thermoplastic Polymer The semicrystalline thermoplastic polymers of the present invention have an enthalpy of fusion (ΔHf) of greater than 5 J / g, determined in a DSC during a step of heating at a rate of 20 K / min according to standard ISO 11357-3:2013.

[0054] The semi-crystalline thermoplastic polymers used according to the invention may be selected from polyolefins, polyamides, polyesters, polyaryletherketones, polyphenylene sulfides, polyacetals, polyimides, polyvinylidene fluorides, and / or mixtures thereof, preferably polyamides.

[0055] Preferably, the semi-crystalline thermoplastic polymer is a polyamide.

[0056] The polyamides may be homopolyamides (i.e., PA "XY" and PA "Z"), copolyamides (i.e., PA "X / Y"), or mixtures thereof.

[0057] "Z"-type polyamides result from the condensation of one or more α,ω-aminocarboxylic acids and / or one or more lactams.

[0058] 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.

[0059] 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.

[0060] Examples of preferred polyamides of this type include PA 6, PA 11 and PA 12.

[0061] "XY"-type polyamides result from the condensation of dicarboxylic acids with aliphatic, cycloaliphatic, or aromatic diamines.

[0062] 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.

[0063] 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 hydrogenated), and 1,2-dodecanedioic acid HOOC-(CH2). 10 An example of such an alkyl group is --COOH.

[0064] 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.

[0065] 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

[0066] Mixtures of polyamides may also be utilized, such as mixtures of aliphatic and semi-aromatic polyamides, or mixtures of aliphatic and cycloaliphatic polyamides.

[0067] 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.

[0068] 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.

[0069] The polyamide blocks may be homopolyamides or copolyamides as described above for homopolyamides and copolyamides.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] Preferably, the powder 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.

[0077] The powders of the invention typically contain from 36% to 99.9% by weight, preferably from 40% to 95% thermoplastic polymer, based on the total weight of the powder.

[0078] Antioxidants Composition (b) according to the present invention is selected from one or more phenolic antioxidants, one or more phosphite / phosphonite antioxidants, one or more thioethers, and / or mixtures thereof.

[0079] Powders of the invention typically contain from 0.1% to 2%, preferably from 0.5% to 1%, by weight of one or more antioxidants based on the total weight of the powder.

[0080] Phenolic Antioxidants According to one embodiment, the powder of the present invention contains a phenolic antioxidant, 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 the company Palmarole; (4,4'-butylidenebis(2-tert-butyl-5-methylphenol), in particular that sold under the name Lowinox® 44B25 by the company Addivant, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), in particular that sold under the name Irganox® 1010 by the company 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 the company 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 the company BASF; - ethylene bis(oxyethylene) bis(3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate), in particular that sold under the name Irganox® 245 by the company 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 the company BASF; N',N'-(2-ethyl-2'-ethoxyphenyl)oxanilide, in particular that sold under the name Tinuvin® 312 by the company BASF; 4,4',4''-[trimethyl-1,3,5-benzenetriyl)tris(methylene)]tris-2,6-bis(1,1-dimethylethyl)phenol, in particular sold under the name Alvinox® 1330 by the company 3V and under the names Hostanox® 245 FF, Hostanox® 245 Pwd by the company Clariant; pentaerythrityl tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), in particular as sold under the names 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 names 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 the company Mayzo; thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], in particular that sold under the name BNX® 1035 by the company Mayzo; octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, in particular that sold under the name BNX® 2086 by the company Mayzo, 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 BNX® 3114 by the company Mayzo. etc.

[0081] Phosphite / Phosphonite Antioxidants According to one embodiment, the powder comprises phosphite / phosphonite antioxidants 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, and cyclic diphosphites derived from pentaerythritol, such as Irgafos® 168 sold by BASF.

[0082] 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 is distearyl pentaerythritol diphosphite.

[0083] Thioether According to one embodiment, the thioether is dilauryl thiodipropionate (DLTDP), ditridecyl thiodipropionate (DTDTDP), distearyl thiodipropionate (DSTDP), dimyristyl thiodipropionate (DMTDP), pentaerythritol tetrakis(3-dodecyl thiopropionate) or pentaerythritol tetrakis(3-lauryl thiopropionate), alkyl (C 12 ~C 14)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'-thiodiethylenebis[3-(3,5-tert-butyl-4-hydroxyphenyl)propionate] phenyl)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), bis(4,6-tert-butyl-1-yl-2-)((4,6-tert-butyl-l-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-alkyl(C 12 / C 14 )thiopropionyloxy]-5-tert-butylphenyl)sulfide, and / or mixtures thereof.

[0084] Preferably, the thioether is selected from the group consisting of dilauryl thiodipropionate (DLTDP), ditridecyl thiodipropionate (DTDTDP), distearyl thiodipropionate (DSTDP), dimyristyl thiodipropionate (DMTDP), pentaerythrityl tetrakis(3-dodecylthiopropionate) or pentaerythrityl tetrakis(3-laurylthiopropionate), and / or mixtures thereof.

[0085] According to one embodiment, the thioether is DLTDP.

[0086] According to one embodiment, the thioether is DSTDP.

[0087] 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.

[0088] 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.

[0089] Metal oxides / metal hydroxides / hydrotalcites Component (c) of the present invention is selected from metal oxides, metal hydroxides, and / or hydrotalcites derived from one or more alkaline earth metals or one or more post-transition metals, preferably one or more post-transition metals.

[0090] According to one embodiment, component (c) is a hydrotalcite derived from one or more alkaline earth metals or one or more post-transition metals, preferably one or more post-transition metals.

[0091] The hydrotalcite according to the invention typically has the formula M a 2+ M b 3+ (OH) 2a+2b - (X i- ) b / i ,yH2O[where M a 2+ represents a divalent metal ion, M b 3+ represents a trivalent metal ion, and X i-represents an anion, typically a carbonate or nitrate ion.

[0092] For example, hydrotalcite that can be used in the powder of the present invention is Mg6Al2CO3(OH) 16 ·4(H2O) may also be used.

[0093] According to one embodiment, component (c) is derived from one or more alkaline earth metals, ie metals of group 2 of the periodic table.

[0094] Preferably, the alkaline earth metals are selected from magnesium, calcium, strontium, and / or barium.

[0095] According to one embodiment, component (c) is derived from one or more post-transition metals.

[0096] The term "post-transition metal" is understood to mean a metallic chemical element located in the periodic table between the transition metals on the left and the metalloids on the right.

[0097] Preferably, the post-transition metal is selected from aluminium, gallium, indium, zinc and / or tin, preferably zinc and / or aluminium.

[0098] Preferably, component (c) is selected from ZnO and / or Al2O3.

[0099] The powder of the present invention generally contains 0.05% to 2%, preferably 0.1% to 1% by weight of component (c) relative to the total weight of the powder.

[0100] Polymer Powder According to one embodiment, the polymer powder according to the invention comprises a thermoplastic polymer (a), a thioether (b), a metal oxide, metal hydroxide and / or hydrotalcite derived from one or more alkaline earth metals or one or more post-transition metals, preferably one or more post-transition metals (c), a filler or reinforcing material (d), and / or one or more further additives (e).

[0101] According to one embodiment, the powder according to the invention comprises: (a) 36% to 99.9%, preferably 40% to 95%, by weight of a thermoplastic polymer; (b) 0.1% to 2%, preferably 0.5% to 1%, by weight of one or more antioxidants; (c) 0.0% to 2%, preferably 0.1% to 1%, by weight of a metal oxide, metal hydroxide, and / or hydrotalcite; (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 30%, preferably 0% to 10%, preferentially 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%.

[0102] Component (e) may contain one or more of these additives.

[0103] Preferably, the polymer powder has a first heat melting point (Mp1) of 80°C to 220°C, preferably 100°C to 200°C.

[0104] The powder may have a crystallization temperature (Tc) of 40°C to 250°C, preferably 45°C to 200°C, for example 60 to 170°C.

[0105] 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.

[0106] The difference between the Tc and Mp of the powder is preferably 20° C. or more, or more preferably 30° C. or more.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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 talc, 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 above for the pigment composition.

[0111] More specifically, the powder of the invention may comprise 0% to 50%, or 5% to 50%, or 10% to 40%, or 10% to 30% by weight of component (d). According to one embodiment, the polymer powder is free of fillers and reinforcing agents.

[0112] Further Additives The polymer powder may, if desired, comprise further additives (e) which are customary in polymer powders used in 3D printing by sintering.

[0113] The powder of the invention may contain 0% to 30% of further additives.

[0114] 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.

[0115] These customary additives may in particular be chosen from flow agents, chain limiters, flame retardants (fire retardants), UV stabilizers, anti-wear agents, light stabilizers, impact modifiers, antistatic agents, pigments, and waxes.

[0116] 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.

[0117] Flame retardants (fire retardants) By way of example, the flame retardant may be selected from halogen-based flame retardants, phosphorus-based flame retardants, inorganic hydrated metal compound flame retardants, nitrogen-containing flame retardants, and silicone-based flame retardants.

[0118] According to one embodiment, the powder of the invention comprises 10% to 30% by weight of flame retardant, preferably 10% to 25% by weight of flame retardant relative to the total mass of the powder.

[0119] According to one embodiment, the flame retardant is of the cyclic phosphonate type and has the general formula (I): TIFF2025501084000001.tif27170[In the formula, j, k, l, and m may be the same or different and represent an integer of 1 to 3; A 1 and A 2 may be the same or different and represent an alkyl group having 1 to 4 carbon atoms or an aryl group having 5 to 7 carbon atoms. It is of the following.

[0120] More preferably, the cyclic phosphonate ester type flame retardant has the general formula (II): TIFF2025501084000002.tif21170[where A 1 and A2 may be the same or different and represent an alkyl group having 1 to 4 carbon atoms or an aryl group having 5 to 7 carbon atoms. It is of the following.

[0121] Even more preferably, the cyclic phosphonate ester type flame retardant has the following formula (III): The file is TIFF2025501084000003.tif23170.

[0122] In general, the flame retardants are powders, typically having a volume median diameter D50 in the range of 1 to 40 μm, preferably 5 to 30 μm.

[0123] Pigments The pigment may be, for example, in the HSS or MJF technique, a pigment having an absorbance of less than 40% for light at a wavelength of 1000 nm, measured according to ASTM standard E1790.

[0124] 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.

[0125] According to one embodiment, the wax is present in the powder in the form of a coating that at least partially covers the polymer powder.

[0126] 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.

[0127] Preferably the chain limiter has a melting point below 180°C.

[0128] The monocarboxylic acid preferably has 2 to 20 carbon atoms. Examples of monocarboxylic acids include acetic acid, propionic acid, benzoic acid, 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, octadecanoic acid, and tetradecanoic acid, preferably stearic acid.

[0129] 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, preferably sebacic acid.

[0130] 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.

[0131] 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.

[0132] The chain limiting agent may be in powder or liquid form at ambient temperature.

[0133] The chain limiting agents according to the invention are preferably added to a medium containing an already formed polyamide and are not incorporated into the composition of the polyamide.

[0134] Preferably, the chain limiter is incorporated into the polyamide powder by any suitable method known to those skilled in the art, such as by dry mixing, liquid mixing, aqueous dispersion, mixing by compounding, diffusion mixing, and the like.

[0135] According to one embodiment, the chain limiter, preferably in powder form, is dry mixed with the polyamide powder.

[0136] 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.

[0137] 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.

[0138] Preferably, the chain limiting agent represents 0.01% to 0.5%, 0.01% to 0.4%, 0.1% to 0.4%, 0.1% to 0.3% by weight relative to the total weight of the thermoplastic polymer, or relative to the total weight of the polyamide if the thermoplastic polymer is a polyamide.

[0139] According to one embodiment, the powder of the invention comprises at least one or more further additives (e) chosen from flame retardants and / or chain limiters.

[0140] Method for preparing polymer powder The polymer powder can be prepared according to conventional methods.

[0141] Commercially available or synthetic thermoplastic polymers, particularly in the form of granules, flakes, or powders, may be utilized for component (a).

[0142] If desired, component (a) can be converted into a powder by known methods, in particular by grinding.

[0143] The grinding may be an ambient temperature grinding.

[0144] Grinding may be cryogenic grinding, in which the material to be ground is cooled, for example by liquid nitrogen, liquid carbon dioxide, or liquid helium, to make the material easier to grind.

[0145] Grinding may be carried out, for example, in a pin mill, a hammer mill, or a whirl mill.

[0146] According to one embodiment, the method for preparing the powder according to the invention comprises the following steps: (i) synthesizing a thermoplastic polymer (a); (ii) grinding the thermoplastic polymer (a) to a powder having a diameter Dv50 of 40 to 150 μm; (iii) introducing, before or after step (ii), one or more antioxidants (b), and metal oxides, metal hydroxides and / or hydrotalcites (c), and optionally one or more components (d)-(e); Includes one or more of:

[0147] The incorporation of some or all of components (b)-(e) into the thermoplastic polymer (component (a)) can be carried out according to methods known to those skilled in the art.

[0148] By way of example, the incorporation may be carried out by melt mixing, for example by extrusion (compounding) and optionally granulation followed by grinding of the granules. The incorporation may be carried out by wet impregnation (for example, see the method described in EP 3325535 B1). Alternatively, the incorporation may be carried out by dry mixing.

[0149] According to one embodiment, the step of incorporation can be carried out during the synthesis of the thermoplastic polymer.

[0150] For example, it is possible to mix the components by co-precipitating polymer (a) from a solution in the presence of some or all of components (b) to (e) (dissolution / precipitation). The conditions can be easily adapted by a person skilled in the art. See, for example, document EP 0863174 B1.

[0151] It is also possible to mix some or all of components (b) through (e) with the prepolymer of component (a) during or after the synthesis of the prepolymer.

[0152] Thus, according to one embodiment, the method for preparing the powder of the present invention comprises: (i) prepolymerizing a monomer(s) of a thermoplastic polymer (a); (ii) grinding to a powder; (iii) subjecting the resulting prepolymer powder to solid-state polycondensation to obtain a polymer powder; (iv) introducing one or more antioxidants (b), metal oxides, metal hydroxides and / or hydrotalcites (c), and optionally one or more components (d)-(e) into the prepolymer powder by melt mixing or dry mixing between steps (i) and (ii) and / or (ii) and (iii) and / or thereafter by dry mixing; Includes.

[0153] Depending on the additive, it is also possible to use several of these methods in the introduction of the additive into the polymer powder.

[0154] The powder thus obtained may then be sieved or subjected to a screening step in order to obtain the desired particle size profile.

[0155] Depending on the particular preparation method, the polymer powder may optionally be subjected to various treatments, in particular thermal or hydraulic treatments.

[0156] Depending on the preparation method, the components can be used in any suitable form.

[0157] 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.

[0158] When the components are added to the polymer by dry blending, 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.

[0159] The invention will now be further illustrated, without being limited thereto, by the following examples. EXAMPLES

[0160] The following examples illustrate the invention without limiting its scope, in which all percentages and parts are expressed by weight, unless otherwise specified.

[0161] Although the tests feature a powder based on polyamide 11, it is understood that the powder according to the invention is not limited to this embodiment and may comprise any type of polymer, in particular polyamide, either alone or as a mixture.

[0162] The basic powder used is one which contains the various components as described above per 100 parts by weight of polyamide 11.

[0163] Low viscosity polyamide 11, hereafter referred to as "prepolymer", was synthesized from 11-aminoundecanoic acid in the presence of water, hypophosphorous acid, and phosphoric acid.

[0164] Polyamide 11 powder was then prepared by grinding the prepolymer, which was then subjected to a hydraulic treatment and subsequent solid-state polycondensation according to the method described in EP 1413595 A. An antioxidant was added during the solid-state polycondensation.

[0165] The polyamide 11 powder has an inherent viscosity equal to 1.20 (in a 0.5% by weight solution in meta-cresol at 20° C.).

[0166] The metal oxides and flow agents are added to the powders by dry mixing in a Henschel IAM 6L mixer, the compounds to be mixed are introduced in the proportions shown in Table 1 below, and the mixture is stirred at 900 rpm for 100 seconds at ambient temperature.

[0167] The measured Dv50 of the powder is 50 μm. [Table 1] TIFF2025501084000004.tif88170PHR = Percentage of Resin (a unit of measure used in formulations that represents the parts of a component per 100 parts by weight of the base powder).

[0168] PTDP is pentaerythrityl tetrakis(3-dodecylthiopropionate). DSTDP is distearyl thiodipropionate. Flow agent: Hydrophobic fumed silica

[0169] Aging test of powder and measurement of yellowness index (YI) a) Solid State The test consists of exposing the example powders in glass bottles placed in a ventilated oven for 72 hours at 177°C. The results are shown in Table 3. This test simulates the exposure conditions that the powders may be subjected to in a 3D device. The measurement of the Yellowness Index (YI) is carried out with a Konica Minolta spectrophotometer with illuminant D65 at 10° in reflection mode with specular reflection included (SCI), according to standard ASTM YI (E313-96) (D65).

[0170] b) Molten state The test consists of exposing the example powders to 220° C. for 2 hours in an aluminium dish placed in a ventilated oven.

[0171] The molten film is then removed and measured by placing it in front of a Leneta form 2A opacity chart. The results are shown in Table 3.

[0172] This test simulates the exposure conditions that a part may be exposed to in a 3D printer as it is built.

[0173] The measurement of the Yellowness Index (YI) is carried out according to standard ASTM YI (E313-96) (D65) with a Konica Minolta spectrocolorimeter with illuminant D65 at 10° in SCI mode. [Table 2] TIFF2025501084000005.tif88170

[0174] During aging tests in the solid and molten state, lower yellowness index values ​​were observed for the powders containing thioethers and metal oxides (Examples 3 to 6) compared to powders without thioethers and metal oxides (Examples 1 and 2) and compared to powders in which the metal oxide is TiO2. Thus, the use of thioethers and metal oxides ZnO and / or Al2O3 in polyamide powders makes it possible to improve the color stability of the powder and of the printing member.

[0175] Breaking Elongation Test The polymer powder thus obtained is then used to print test specimens in the shape of ISO 527-1A. These test specimens are made along the Z axis (vertical axis, FIG. 1) on an MJF5200 machine sold and constructed by HP. The conditions used are the same for all prints.

[0176] The following models were prepared using Materialize Magics 22.0 software:

[0177] Test specimens were then prepared according to this model, as shown in FIG.

[0178] During the build, the temperature of the powder at the surface of the build tank is set and measured at the surface by an infrared heat sensor.

[0179] The build time for the two blocks of specimens is approximately 12 hours, and they are left to cool to ambient temperature for 48 hours.

[0180] The specimens of the lower block were prepared first, therefore they were subjected to thermal oxidation for a longer time.

[0181] The test specimens of the lower block thus obtained are subsequently characterized with regard to their mechanical properties: more specifically, the breaking elongation of the test specimens is measured in an Instrom 5966 apparatus according to standard ISO 527-2.

[0182] [Figure 2] shows the percentage of specimens having an elongation greater than x%, where x is the abscissa of the graph.

[0183] When compared to the exact same powder without added metal oxide (powder of Comparative Example 1), a higher percentage of specimens with elongation <10% is observed.

[0184] It is also observed that the addition of Al2O3 (example 4) or ZnO (example 3) reduces the percentage of "brittle" specimens (0% of specimens with an elongation <12%), thereby reducing the variability of the mechanical properties of the sintered parts. It is therefore possible to provide powders that make it possible to obtain printed parts with improved mechanical properties, while avoiding the production of parts with low elongation, i.e. <10%.

[0185] Tests were carried out on powders containing flame retardants.

[0186] Example 8 (for comparison) contains 83% by weight of the powder according to Example 1 and 17% by weight of a compound sold under the name Aflammit® PCO 910 with the following formula: TIFF2025501084000006.tif21170 and a cyclic phosphonate ester type flame retardant dry blend (using a Henschel mixer). Weight percentages are based on the total weight of the blend.

[0187] Example 9 is a dry mix of the powder of Example 8 with ZnO added at 0.25 wt % based on the total weight of the powder of Example 8.

[0188] The melt aging test was carried out under the above conditions, the only difference being that the test was carried out for 1 hour. [Table 3] TIFF2025501084000007.tif35170

[0189] Lower yellowness index values ​​were observed for the powder containing metal oxide (Example 9) compared to the powder without metal oxide (Example 8). Thus, the use of the metal oxide ZnO in the flame retardant-containing polyamide powder made it possible to improve the color stability of the printing member.

Claims

1. 1. A polymer powder suitable for 3D printing by sintering, comprising: (a) a semi-crystalline thermoplastic polymer; (b) one or more antioxidants, and (c) metal oxides, metal hydroxides, and / or hydrotalcites derived from one or more alkaline earth metals or one or more post-transition metals, preferably one or more post-transition metals; Powder, including

2. 2. The powder according to claim 1, wherein component (c) is derived from one or more metals selected from aluminum, gallium, indium, magnesium, calcium, zinc, and / or tin, preferably selected from zinc and / or aluminum.

3. Component (c) is ZnO and Al ２ O ３ 2. The powder of claim 1, wherein the powder is selected from:

4. 2. The powder of claim 1, wherein component (b) is selected from one or more phenolic antioxidants, one or more phosphite / phosphonite antioxidants, one or more thioethers, and / or mixtures thereof.

5. 5. The powder of claim 4, wherein component (b) is selected from one or more phenolic antioxidants, one or more thioethers, and / or mixtures thereof.

6. 2. The powder according to claim 1, wherein the semi-crystalline thermoplastic polymer is selected from polyolefins, polyamides, polyesters, polyaryletherketones, polyphenylene sulfides, polyacetals, polyimides, polyvinylidene fluorides, and / or mixtures thereof, preferably polyamides.

7. 7. The powder according to claim 6, wherein the polyamide is selected from homopolyamides, copolyamides, copolymers having polyamide blocks and polyether blocks (PEBA), and / or mixtures thereof.

8. 2. The powder of claim 1, comprising a filler or reinforcing material (d) and / or one or more further additives (e).

9. (a) 36% to 99.9%, preferably 40% to 95%, by weight of a thermoplastic polymer; (b) 0.1% to 2%, preferably 0.2% to 1%, by weight of one or more antioxidants; (c) 0.05% to 5%, preferably 0.1% to 1%, by weight of a metal oxide, metal hydroxide, and / or hydrotalcite; (d) 0% to 50%, preferably 10% to 50%, especially 20% to 40% by weight of a filler or reinforcing material; and (e) 0% to 30%, preferably 0% to 10%, preferentially 0.1% to 7.5%, in particular 1% to 5% by weight of further additives 2. The powder of claim 1, wherein the percentages of components (a), (b), (c), (d), and (e) total 100%.

10. 2. The powder of claim 1 having a diameter Dv50 of 40 to 150 μm.

11. (i) synthesizing a thermoplastic polymer (a); (ii) grinding the thermoplastic polymer (a) to a powder having a diameter Dv50 of 40 to 150 μm; (iii) before or after step (ii), introducing one or more antioxidants (b), and metal oxides, metal hydroxides, and / or hydrotalcites (c), and optionally one or more components (d)-(e).

10. A method for preparing the powder of claim 1, comprising one or more of:

12. 10. A method for preparing the powder of claim 1, comprising: (i) prepolymerizing the monomer(s) of thermoplastic polymer (a); (ii) grinding to a powder; (iii) subjecting the resulting prepolymer powder to solid-state polycondensation to obtain a polymer powder; (iv) introducing one or more antioxidants (b), metal oxides, metal hydroxides, and / or hydrotalcites (c), and optionally one or more components (d)-(e) into the prepolymer powder by melt-mixing or dry-mixing between steps (i) and (ii) and / or (ii) and (iii) and / or thereafter by dry-mixing; A method comprising:

13. 1. Use of metal oxides, metal hydroxides and / or hydrotalcites derived from one or more alkaline earth metals or one or more post-transition metals, preferably one or more post-transition metals, in a polymer powder suitable for 3D printing by sintering, to improve the thermal stability of said powder, in particular to reduce yellowing.

14. Use of metal oxides, metal hydroxides and / or hydrotalcites derived from one or more alkaline earth metals or one or more post-transition metals, preferably one or more post-transition metals, in a polymer powder suitable for 3D printing by sintering, to improve the mechanical properties, in particular the elongation at break, of a printed member produced from said powder.

15. 14. Use according to claim 13, wherein the powder comprises one or more antioxidants, preferably selected from one or more phenolic antioxidants, one or more phosphite / phosphonite antioxidants, one or more thioethers, and / or mixtures thereof.

16. The metal oxide is ZnO and Al ２ O ３ The use according to claim 13, wherein the compound is selected from the group consisting of:

17. 10. A 3D printing method, preferably by electromagnetic wave induced sintering, 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 or a different printing method.

18. 18. An article of manufacture obtainable by the 3D printing method of claim 17.

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