FR3125051A1 - Thermoplastic polymer powder for construction of 3D articles - Google Patents

Abstract

The present invention relates to a polymer powder suitable for 3D printing by sintering. More particularly, the present invention relates to a powder comprising a particular thermoplastic polymer composition (component (a)), making it possible to obtain articles manufactured by 3D printing from the latter having an improved mechanical property. The invention also relates to its method of manufacture and its use for the manufacture of articles by 3D printing (also called "printed parts").

Description

Thermoplastic polymer powder for construction of 3D articles

FIELD OF THE INVENTION

The present invention relates to a polymer powder suitable for 3D printing by sintering. More particularly, the present invention relates to a powder comprising a thermoplastic polymer composition (component (a)) making it possible to obtain articles manufactured by 3D printing having improved mechanical properties. The invention also relates to its manufacturing process and its use for the manufacture of articles by 3D printing (also called “printed parts”).

TECHNICAL BACKGROUND

There are different 3D printing techniques using polymer powder. The principle is generally based on the agglomeration of powder, layer by layer by fusion of the latter (hereinafter "sintering") caused by a source of electromagnetic energy, for example a laser beam, infrared radiation, a UV radiation, or any source of electromagnetic radiation to melt the powder layer by layer to make three-dimensional objects.

Mention may be made of the technology of selective sintering by a laser beam (SLS). Mention may also be made of sintering technologies using an absorber, for example the technologies known by the names “ High Speed Sintering ” in English (HSS) and “ Multi-Jet Fusion ” in English (MJF).

To perform the printing, the polymer powder, preheated in a reservoir tank, is introduced into the construction enclosure, spread in a thin layer (called the "bed") on a horizontal plate and then heated to the temperature of the bed.

The bed temperature is generally located in the interval between the crystallization temperature (Tc) and the melting temperature (Tf) of the polymer.

Generally, for polymers with sharp melting temperatures, especially when the enthalpy of fusion is high (e.g. > 60 J/g), the bed temperature can be set between Tf-5°C and Tf-20°C .

However, in the case of elastomers and polymers having spread melting temperatures, in particular when the enthalpy of fusion is low (e.g. < 60 J/g), the temperature of the bed is generally set at a lower temperature, for example at Tf-30°C, to avoid the phenomenon of caking.

During printing, the thin layer of polymer powder is selectively and briefly irradiated by a source of electromagnetic energy, for example, a laser beam in an SLS process, or infrared radiation in an MJF process.

The result is that the impacted powder particles melt to form material points of the article to be printed. When the printing of the layer is finished, we lower the plate, and we cover the bed with a new thin layer of powder. The steps are repeated with a succession of layers of powders until the solid part is obtained.

Undesirable porosity has often been observed in the printed parts. This porosity is due in whole or in part to poor coalescence of the molten powder grains during the printing process.

Too much porosity is detrimental to the mechanical properties. For example, a much lower elongation at break can be observed for a 3D printed part compared to a part of the same composition but obtained by an injection process.

Poor powder coalescence can also create surface defects.

To solve this coalescence problem, different solutions have been proposed in the past.

For example, document US 10,596,728 B2 proposes a powder suitable for PBF to coat the powder with a hydrophobic substance to lower the surface energy of the latter to less than 35 mN/m.

A prior preparation step for coating the powder with a hydrophobic substance is therefore required.

Or, it is proposed, for 3D printing in MJF, to use a fusion agent including an energy absorber to absorb electromagnetic radiation to coalesce the powders, as described in:

- document WO 19245518 describing a thermoplastic elastomer kit having an avalanche angle of 49 to 59°C, a cut energy of 55 to 78 kJ/kg, and an avalanche energy of 10 to 27 kJ/kg, and a fusion agent,
- document WO 19182614 describing a kit comprising a polyether block polymer and a polyamide block having a relative viscosity in solution of 1.55 to 1.80, and a melting agent,
- Document WO 19245517 describing a kit comprising a thermoplastic elastomer in which at least 70% of individuals have an aspect ratio of 0.75 to 1 and a fusion agent.

There is therefore a need to be able to manufacture parts, from a thermoplastic powder, by 3D printing by sintering, with good mechanical properties and without the aforementioned constraints.

The present invention makes it possible to meet this need.

According to a first aspect, the subject of the invention is a polymer powder suitable for 3D printing by sintering, comprising:
(a) a thermoplastic polymer composition; and optionally,
(b) one or more fillers or reinforcements,
(c) one or more additives,
where the G"2/G"1 ratio of said powder is less than or equal to 3.00, preferably less than or equal to 2.90,
G"1 being the loss modulus at the melting temperature (Tf) of the powder, when the powder is heated to Tm+40°C for 2 minutes and is then cooled down to Tm at a rate of -5° c/min,
G"2 being the loss modulus at - 30°C of the Tf of the powder, when the powder is heated to Tf+ 40°C for 2 minutes and is then cooled down to Tf-30°C at a rate of -5°C/min,,
the values of G"2, G"1 being measured according to standard ISO 6721-10: part 10, at an angular frequency of 6.28 rad/sec.

Preferably, the G"2/G"1 ratio is less than or equal to 2.80.

Generally, the ratio G″2/G″1 is greater than or equal to 2.00, preferably greater than or equal to 2.10.

According to one embodiment, G"1 is less than or equal to 100,000 Pa, preferably less than or equal to 50,000 Pa.

According to one embodiment, G"2 is less than or equal to 200,000 Pa, preferably less than or equal to 100,000 Pa.

It was observed that when the G"2/G"1 ratio was less than 3.00, the coalescence of the powders could take place sufficiently, during its cooling from the molten state. The printed parts then have a better elongation at break, comparable with the printed parts obtained by injection.

When the G"2/ G"1 ratio is greater than 3.00, the molten powders congeal too quickly, preventing sufficient coalescence between them, creating undesirable porosity in the printed part, which leads to poor elongation at break .

This is particularly suitable for elastomers and polymers with spread melting temperatures, especially when the melting enthalpy is low (e.g. < 60 J/g), i.e., in the case where the bed temperature is set from relatively far from Tf, typically at Tf-30°C.

The present invention therefore proposes a thermoplastic powder making it possible to obtain printed parts of good quality, having improved coalescence, and thus improved mechanical properties.

Advantageously, the powder has a diameter Dv50 as measured according to standard ISO 9276 - parts 1 to 6, from 40 to 150 μm.

Advantageously, the powder has an inherent viscosity greater than or equal to 1.0, preferably greater than or equal to 1.1, or 1.2, and less than or equal to 1.8, preferably less than or equal to 1.7 , or 1.6, or at 1.5.

The powder having an inherent viscosity in the range described above advantageously improves the mechanical properties of the printed parts. Indeed, it has been observed that when the inherent viscosity is too low, namely, less than 1.0, the mechanical properties of the printed parts become insufficient for certain end uses. When the inherent viscosity is greater than 1.8, the coalescence of the powders can be impacted, thus creating porosities in the final parts and poor mechanical properties.

Preferably, the polymer composition (a) has an enthalpy of fusion less than or equal to 60 J/g, preferably less than or equal to 55 J/g.

Preferably, composition (a) has an enthalpy of fusion of 10 to 15 J/g; or from 15 to 20 J/g; or from 20 to 25 J/g; or from 25 to 30 J/g; or from 30 to 35 J/g; or from 35 to 40 J/g; or from or from 40 to 45 J/g; or from 45 to 50 J/g; or from 50 to 55 J/g; or 55 to 60 J/g.

According to one embodiment, the polymer composition (a) comprises at least one thermoplastic polymer chosen from polypropylene (PP), polyolefin, polyamide (PA), polyester, polyarylether ketone (PAEK), polyphenylene sulphide, polyacetal, polyimide, polymer vinylidene fluoride and/or their mixture, preferably chosen from PP, PA and/or PAEK.

According to a particularly advantageous embodiment, the polymer composition (a) comprises at least one thermoplastic elastomer.

Preferably, the polymer composition (a) comprises a thermoplastic elastomer chosen from the group consisting of block copolymers SBS, SIS, SEBS, TPU, COPE and PEBA as well as their mixtures and alloys, and in particular, it comprises a PEBA. Alternatively, the polymer composition (a) may comprise a thermoplastic elastomer chosen from TPO, PP/NBR, PO/CPE-VD, EVA/VC and PVC/NBR blends.

The present invention thus proposes a particular thermoplastic powder for printing which makes it possible to improve the coalescence of the powders, by reducing the porosity of the printed part, thus improving the mechanical property of the latter, in particular in terms of the elongation at breaking.

According to a second aspect, the invention relates to a method for preparing such a powder, comprising the steps of:
(i) grinding a polymer composition (a) into a powder with a volume average diameter Dv50 of 40 to 150 µm, before or after,
(ii) introduction of at least one or more fillers and/one or more additives, where appropriate.

According to another aspect, the invention relates to the use of such a powder for 3D printing by sintering, in particular chosen from the selective laser sintering process (SLS), the MJF type sintering process (Multi Jet Fusion ) and the HSS (High Speed Sintering) type sintering process.

According to another aspect, the invention finally relates to an article obtained by 3D printing by sintering such a powder.

Description of the invention

Definition

In the present description of the invention, including in the examples below:
- The term " thermoplastic polymer " is understood to denote a polymer having the property of softening when it is sufficiently heated, and which, on cooling, becomes hard again;

- The term " thermoplastic elastomer " is understood to denote a polymer comprising flexible segments and rigid segments, for example in the form of a block copolymer, in which the rigid segments which disappear when the temperature increases. Alternatively, they may be mixtures combining the presence of a flexible elastomeric phase, crosslinked or not, dispersed in a rigid thermoplastic continuous phase. The blends may in particular be blends of a thermoplastic polymer with an elastomer;

- The term " copolymer " is understood to denote a polymer resulting from the copolymerization of at least two types of chemically different monomers, called comonomers. A copolymer is therefore formed from at least two repeating units. It can also be formed from three or more repeating patterns. More specifically, the term “ block copolymer ” or “ block copolymer ” is understood to denote copolymers in the aforementioned sense, in which at least two distinct monomer blocks are linked by a covalent bond. The length of the blocks can be variable. Preferably the blocks are composed of 1 to 1000, preferably 1 to 100, and especially 1 to 50 repeat units, respectively. The bond between the two monomer blocks can sometimes require an intermediate non-repeating unit called a junction block.

- The term " melting temperature " means the temperature at which a partially crystalline polymer changes to the viscous liquid state, as measured during the first heating (Tf1) by differential calorimetric analysis (DSC) according to the NF standard EN ISO 11 357-3 using a heating rate of 20°C/min.

- The term " crystallization temperature " means the temperature at which a partially crystalline polymer changes from the viscous liquid state to the solid state, as measured by differential scanning calorimetry (DSC) according to standard NF EN ISO 11 357-3 using a cooling rate of 20°C/min.

- the term " glass transition temperature " means the temperature at which a polymer changes from a rubbery state to a glassy state, or vice versa, as measured by differential scanning calorimetry (DSC) according to standard NF EN ISO 11357-2 using a heating rate of 20° C./min;

- The term “ enthalpy of fusion ” is understood to denote the heat consumed during the solid/liquid transition of the thermoplastic elastomer, as measured by differential scanning calorimetry, according to standard ISO 11257-3: 1999;

- the term " average diameter by volume " or " Dv " is also understood to mean the average diameter by volume of a pulverulent material, as measured according to standard ISO 9276 - parts 1 to 6: "Representation of data obtained by analysis particle size". There are different diameters. More specifically, the Dv50 designates the median diameter by volume, and the Dv10 and Dv90 respectively designate the average diameters by volume below which 10 or 90% by volume of the particles are located. The volume mean diameter can be measured in particular by means of a laser particle sizer, for example a laser particle sizer (Sympatec Helos) and software (Fraunhofer) making it possible to obtain the volumetric distribution of a powder and to deduce the Dv10 therefrom. , Dv50 and Dv90;

- The term " inherent viscosity " means the viscosity as measured according to the following steps:
- Sampling of polymer samples between 0.07 and 0.10 g and preferably 0.15 g maximum,
- Addition of a sufficient quantity of m-cresol solvent by weighing in order 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 complete dissolution of the polymer;
- Cooling the solution to room temperature, preferably for at least 30 minutes;
- Measurement of the flow time t0 of the pure solvent and of the flow time t of the solution using a viscometer in a micro-Ubbelohde tube in a thermostated bath regulated at 20°C ± 0.05°C,
- Calculation of the viscosity according to the formula 1 / C x Ln (t/t0), where C represents the concentration and Ln the natural logarithm,
For each sample, three measurements are carried out on different solutions and then the average is calculated.

- the term “ loss modulus” is understood to refer to the modulus measured in an oscillatory rheometer according to standard ISO 6721-10: 2015 – Part 10 under the following conditions:
Device used: ARES G2 (TA Instruments)
Geometry: 25mm diameter parallel planes
Angular frequency: 1Hz (6.28 rad/sec)
Distortion: 2%
Atmosphere: Nitrogen sweep

- The nomenclature used to designate the polyamides according to the present invention follows the ISO 1874-1 standard.

- The molar mass in number Mn of the polymers described, and of the constituent blocks of the thermoplastic elastomers, can be measured before the copolymerization by steric exclusion chromatography (SEC) according to ISO 16014-1:2012 using hexafluoroisopropanol (HFIP) as eluant.

Thermoplastic polymer composition (a)

The thermoplastic polymer composition can in principle be of any nature, subject to having the properties, in particular thermal properties, suitable for 3D printing by sintering.

The polymer composition (a) can comprise at least one polymer chosen from polyolefin, polyamide, polyester, polyarylether ketone (PAEK), polyphenylene sulphide, polyacetal, polyimide, vinylidene fluoride polymer and/or their mixture.

According to one embodiment, the polymer composition (a) comprises a polyarylether ketone (PAEK), chosen from poly-ether-ketone-ketone (PEKK), poly-ether-ether-ketone (PEEK), poly-ether-ketone (PEK), poly-ether-ether-ketone-ketone (PEEKK), a poly-ether-ether-ether-ketone (PEEK), poly-ether-diphenyl-ether-ketone (PEDEK), mixtures thereof and/or their copolymers.

More specificly :
the PEKK comprises unit(s) of formula: -Ph-O-Ph-C(O)-Ph-C(O)-;
the PEEK comprises unit(s) of formula: -Ph-O-Ph-O-Ph-C(O)-;
the PEK comprises unit(s) of formula: -Ph-O-Ph-C(O)-;
the PEEKK comprises unit(s) of formula: -Ph-O-Ph-O-Ph-C(O)-Ph-C(O)-;
PEEEK comprises unit(s) of formula: -Ph-O-Ph-O-Ph-O-Ph-C(O)-;
the PEDEK comprises unit(s) of formula -Ph-O-Ph-Ph-O-Ph-C(O)-;
in which: Ph represents a phenylene group and –C(O)- a carbonyl group, each of the phenylenes being able independently to be of the ortho (1-2), meta (1-3) or para (1-4) type, preferentially being meta or para type.

According to one embodiment, the polymer composition (a) comprises a vinylidene fluoride polymer which may be a homopolymer or a copolymer obtained by polymerization of the VDF monomer with at least one other comonomer, the at least one other comonomer may be a halogenated alkene, and more preferably a fluorinated alkene. Mention may in particular be made of halogenated propenes or ethylenes, and more particularly fluoroethylene (or vinyl fluoride), chlorofluoroethylenes (1-chloro-1-fluoroethylene and 1-chloro-2-fluoroethylene), trifluoroethylene, chlorodifluoroethylenes (in particular 1 -chloro-2,2-difluoroethylene), 1-bromo-2,2-difluoroethylene, bromotrifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, trifluoropropenes (in particular 3,3,3-trifluoropropene), tetrafluoropropenes (in particular 2 ,3,3,3-tetrafluoropropene), chlorotrifluoropropenes (in particular 2-chloro-3,3,3-trifluoropropene), pentafluoropropenes (in particular 1,1,3,3,3-pentafluoropropene or 1,2, 3,3,3-pentafluoropropene) and hexafluoropropene also called hexafluoropropylene. It may also be a perfluoroalkylvinylether, of general formula R _f -O-CF-CF ₂ , R _f being an alkyl group, preferably C1 to C4. Preferred examples are PPVE (perfluoropropylvinylether) and PMVE (perfluoromethylvinylether).

Such polymers are commercially available, for example the products marketed by Arkema under the name Dyflor®, Kynar®, Solef®.

According to one embodiment, the polymer composition (a) comprises a polyamide.

The polyamide can be a homopolyamide, a copolyamide, or mixtures thereof.

According to one embodiment, the polyamide comes from the condensation of one or more monomers of the α,ω-aminocarboxylic acid type or of one or more monomers of the lactam type (“Z” type).

By way of example of α,ω-amino carboxylic acid, mention may be made of alpha-omega amino acids, such as aminocaproic, amino-7-heptanoic, amino-11-undecanoic, n-heptyl-11-aminoundecanoic and amino-12-dodecanoic.

By way of example of lactams, mention may be made of those having from 3 to 12 carbon atoms on the main ring and which may be substituted. Mention may be made, for example, of β,β-dimethylpropriolactam, α,α-dimethylpropriolactam, amylolactam, caprolactam, capryllactam, oenantholactam, 2-pyrrolidone and lauryllactam.

By way of example of this type of preferred polyamides, mention may be made of PA 6, PA 11 and PA 12, as well as mixtures thereof.

According to one embodiment, the polyamide comes from the condensation of a dicarboxylic acid with an aliphatic, cycloaliphatic or aromatic diamine (“XY” type, X representing the number of carbon atoms of the diamine and Y representing the number of carbon atoms of the dicarboxylic acid).

By way of example of a diamine, mention may be made of aliphatic diamines having from 6 to 12 atoms, the diamine X possibly also being aryl and/or saturated cyclic. Examples include hexamethylenediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, 1,5 diaminohexane, 2,2,4-trimethyl-1,6 -diamino-hexane, diamine polyols, isophorone diamine (IPD), methyl pentamethylenediamine (MPDM), bis(aminocyclohexyl) methane (BACM), bis(3-methyl-4 aminocyclohexyl) methane (BMACM), methoxylyenediamine, trimethylhexamethylene diamine.

By way of example of a dicarboxylic acid, mention may be made of the acids Y having between 4 and 18 carbon atoms, preferably from 9 to 12 carbon atoms. Mention may be made, for example, of adipic acid, sebacic acid, azelaic acid, suberic acid, isophthalic acid, butanedioic acid, 1,4-cyclohexyldicarboxylic acid, terephthalic acid, sodium or lithium salt of sulfoisophthalic acid, dimerized fatty acids (especially those having a dimer content of at least 98% and/or hydrogenated) and 1,2-dodecanedioic acid HOOC-( CH ₂ ) ₁₀ -COOH.

As an example of this type of preferred polyamides, PA 612 resulting from the condensation of hexamethylenediamine and 1,12-dodecanedioic acid; PA 613 resulting from the condensation of hexamethylene diamine 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.

According to one embodiment, the polyamide is a copolyamide resulting from the polycondensation:
- at least two different monomers chosen from different α,ω-amino carboxylic acids or two different lactams or a lactam and an α,ω-amino carboxylic acid with different carbon numbers; Or
-at least one α,ω-amino carboxylic acid (or a lactam), at least one diamine and at least one dicarboxylic acid, or
- an aliphatic diamine with an aliphatic dicarboxylic acid and at least one other monomer chosen from aliphatic diamines different from the previous one and aliphatic diacids different from the previous one.

The notation PA Z/XY, PA Z/Z’, PA Z/XY/X’Y’, PA Z/Z’/XY, PA Z/Z’/XY/X’Y’, etc. refers to copolyamides in which XY, Z, X'Y', Z' etc. represent homopolyamide monomers XY, Z as described above, X'Y' being identical to or different from XY, Z' being identical to or different from Z.

According to one embodiment, one of the monomers constituting a copolyamide can represent more than 50%, preferably more than 60% by mass of the total mixture of monomers.

According to one embodiment, one of the monomers constituting a copolyamide can represent less than 90%, preferably less than 80% by mass of the total mixture of monomers.

Examples of particularly preferred copolyamides are the blocks PA 6/11, PA 6/12, PA 11/12, PA 6/11/12, PA 6/66/12, PA 6/1010, PA 6/1012 , PA 6/1010/1012, PA 6/1012/12, PA 6/66/11/12, PA 6/1010/1012/1014, as well as mixtures thereof.

It is also possible to use mixtures of polyamides, which may be mixtures of aliphatic polyamides and of semi-aromatic polyamides and mixtures of aliphatic polyamides and of cycloaliphatic polyamides.

Thermoplastic elastomer

According to one embodiment, the polymer composition (a) according to the invention comprises at least one thermoplastic elastomer.

The thermoplastic elastomer can in principle be of any kind, provided it has the properties, in particular thermal properties, suitable for 3D printing by sintering.

The thermoplastic elastomer may in particular be a copolymer with styrenic blocks (TPS), in particular with polystyrene and polybutadiene (SBS) blocks, a copolymer with polystyrene and polyisoprene (SIS) blocks, a copolymer with polystyrene and poly(ethylene/butylene) blocks ( SEBS), a copolymer with isocyanate and ether or ester blocks (TPU), a copolymer with polyester and polyester or polyether blocks (COPE), or even a copolymer with polyamide and polyether blocks (PEBA).

Such thermoplastic elastomers are commercially available, for example products under the names CAWITON®, THERMOLAST K®, THERMOLAST M®, Sofprene®, Dryflex® and Laprene ® (TPS), Desmopan® or Elastollan® (TPU), Santoprene®, Termoton®, Solprene®, THERMOLAST V®, Vegaprene®, or Forprene® (TPV), and For-Tec E® or Engage. Ninjaflex® (TPO).

According to a particularly advantageous embodiment, the thermoplastic elastomer is a “PEBA” copolymer. These copolymers are in particular marketed by Arkema France under the name Pebax®, by Evonik® under the name Vestamid®, by EMS under the name Grilamid®, and by Sanyo under the name Pelestat®.

Alternatively, it may be a mixture of a flexible polymer phase dispersed in a continuous phase of rigid polymer. Mention may be made, by way of example of such mixtures, of an EPDM dispersed in a polyolefin (TPO) or a thermoplastic vulcanizate (TPV), a copolymer of butadiene and acrylonitrile (NBR), vulcanized or not, dispersed in a polypropylene (PP/NBR ), a chlorinated polyethylene dispersed in a polyolefin (PO/CPE-VD), an EVA dispersed in vinylidene chloride (EVA/VC), or a copolymer of butadiene and acrylonitrile (NBR), vulcanized or not, dispersed in a polyvinyl chloride (PVC/NBR).

The elastomer present in component (a) of the powder of the invention preferably has a melting point (Tm) ranging from 100 to 300°C, and preferably from 120 to 200°C.

Furthermore, the thermoplastic elastomer preferably has a crystallization temperature (Tc) ranging from 40 to 250°C, and preferably from 45 to 200°C, for example from 45 to 150°C.

Typically, Tf and Tc are determined directly from the polymer powder. When dealing with a polymer blend, the retained Tf is the lowest Tf in the polymer blend, and the retained Tc will be the highest Tc in the polymer blend.

Finally, the difference between the Tc and the Tf of the thermoplastic elastomer is preferably greater than or equal to 20°C, preferably greater than or equal to 30°C, more preferably greater than or equal to 40°C, or to 50°C, or at 60°C, or at 70°C, or at 80°C.

Component (a) may comprise one or more thermoplastic polymers as described above.

According to one embodiment, component (a) may further comprise up to 50% by weight of one or more additional thermoplastic polymers. Preferably, however, component (a) consists only of thermoplastic elastomer.

The thermoplastic elastomer may in particular have an enthalpy of fusion of between 10 and 45 J/g. In particular, it can be from 10 to 15 J/g; or from 15 to 20 J/g; or from 20 to 25 J/g; or from 25 to 30 J/g; or from 30 to 35 J/g; or 35 to 40 J/g, or 40 to 45 J/g.

Copolymer with polyamide blocks and polyether blocks (PEBA)

The copolymer with polyamide blocks and with polyether blocks of the present invention can preferably be a linear (non-crosslinked) copolymer.

PEBA copolymers can result from the polycondensation of polyamide (PA) blocks with reactive ends with polyether (PE) blocks with reactive ends, such as:
1) polyamide blocks with diamine chain ends with polyoxyalkylene blocks with dicarboxylic chain ends;
2) dicarboxylic chain-ended polyamide blocks with diamine chain-ended polyoxyalkylene blocks;
3) polyamide blocks with dicarboxylic chain ends with polyetherdiols, the products obtained being, in this particular case, polyetheresteramides.

Polyamide blocks with dicarboxylic chain ends come, for example, from the condensation of polyamide precursors in the presence of a chain-limiting dicarboxylic acid. Polyamide blocks with diamine chain ends come, for example, from the condensation of polyamide precursors in the presence of a diamine chain limiter.

Two types of polyamide blocks can advantageously be used.

AccordingA first kind (variant I) , the polyamide blocks are copolyamide blocks.

The block copolymers (COPA) can be a copolyamide as described in the “polyamide” part above.

According to this variant I, the number-average molar mass (Mn) of the polyamide blocks in the PEBA copolymer is from 400 to 20,000 g/mol, more preferably from 500 to 10,000 g/mol, preferably from 500 to 4,000 g/mol, and even more preferably from 600 to 2000 g/mol. For example, the number-average molar mass of the polyamide blocks in the PEBA copolymer can be from 400 to 1000 g/mol, or from 1000 to 1500 g/mol, or from 1500 to 2000 g/mol, or from 2000 to 2500 g /mol, or from 2500 to 3000 g/mol, or from 3000 to 3500 g/mol, or from 3500 to 4000 g/mol, or from 4000 to 5000 g/mol, or from 5000 to 6000 g/mol, or from 6000 to 7000 g/mol, or 7000 to 8000 g/mol, or 8000 to 9000 g/mol, or 9000 to 10000 g/mol, or 10000 to 11000 g/mol, or 11000 to 12000 g/ mol, or from 12000 to 13000 g/mol, or from 13000 to 14000 g/mol, or from 14000 to 15000 g/mol, or from 15000 to 16000 g/mol, or from 16000 to 17000 g/mol, or from 17000 at 18000 g/mol, or from 18000 to 19000 g/mol, or from 19000 to 20000 g/mol.

According to this variant I, the number-average molar mass (Mn) of the polyether blocks is from 100 to 6000 g/mol, more preferentially from 200 to 3000 g/mol, and even more preferentially from 200 to 2000 g/mol. The number average molar mass of the polyether blocks can be from 100 to 200 g/mol, or from 200 to 500 g/mol, or from 500 to 800 g/mol, or from 800 to 1000 g/mol, or from 1000 to 1500 g/mol, or 1500 to 2000 g/mol, or 2000 to 2500 g/mol, or 2500 to 3000 g/mol, or 3000 to 3500 g/mol, or 3500 to 4000 g/mol, or from 4000 to 4500 g/mol, or from 4500 to 5000 g/mol, or from 5000 to 5500 g/mol, or from 5500 to 6000 g/mol.

According to one embodiment, the preferred PEBA copolymers are copolymers comprising blocks of copolyamides as defined above (variant I) and blocks derived from PTMG, for example: PA 6/11 and derived from PTMG, PA 6/ 12 and derived from PTMG, PA 11/12 and derived from PTMG, PA 6/11/12 and derived from PTMG, PA 6/66/12 and derived from PTMG, PA 6/1010 and derived from PTMG, PA 6/1012 and derived from PTMG, PA 6/1010/1012 and derived from PTMG, PA 6/1012/12 and derived from PTMG.

According to a second type (variant II ) , the polyamide blocks result from the condensation of an α,ω-aminocarboxylic acid or of a lactam and the number-average molar mass (Mn) of the polyamide blocks in the PEBA is preferably 400 to 1500 g/mol, more preferentially from 500 to 1200 g/mol, preferentially from 500 to 1000 g/mol.

The polyamide blocks according to this variant are polyamides of the “Z” type as described in the “polyamide” part below.

For example, the number-average molar mass (Mn) of the polyamide blocks in the PEBA copolymer can be from 400 to 600 g/mol, or from 600 to 900 g/mol, or from 900 to 1000 g/mol, or from 1000 to 1200 g/mol, or from 1200 to 1300 g/mol, or from 1300 to 1400 g/mol, or from 1400 to 1500 g/mol.

According to this embodiment, the number-average molar mass (Mn) of the polyether blocks is preferably from 400 to 1500 g/mol, more preferably from 500 to 1200 g/mol, and even more preferably from 500 to 1000 g/mol .

For example, the number average molar mass of the polyether blocks can be from 400 to 600 g/mol, or from 600 to 900 g/mol, or from 900 to 1000 g/mol, or from 1000 to 1200 g/mol, or from 1200 to 1300 g/mol, or from 1300 to 1400 g/mol, or from 1400 to 1500 g/mol.

According to this embodiment, the preferred PEBA copolymers are PA 11, PA 12, PA 6, and mixtures thereof.

The polyether blocks of PEBA essentially comprise or consist of alkylene oxide units. The polyether blocks can be derived from alkylene glycols such as PEG (polyethylene glycol), PPG (propylene glycol), PO3G (polytrimethylene glycol) or PTMG (polytetramethylene glycol), preferably PTMG.

They can also be derived from copolyethers comprising different alkylene oxides distributed in the chain in a regular manner, in particular in blocks, or in a random manner.

The polyether blocks can also be obtained by oxyethylation of bisphenols, such as bisphenol A. These products are described in particular in document EP 613919 A1.

The polyether blocks can also be ethoxylated primary amines, such as the products of formula:

where m and n are integers between 1 and 20 and x an integer between 8 and 18.

These products are, for example, commercially available under the brand NORAMOX® from the company CECA and under the brand GENAMIN® from the company CLARIANT.

Finally, the polyether blocks can comprise or consist of polyoxyalkylene blocks with ends of NH ₂ chains. Such blocks can be obtained by cyanoacetylation of polyetherdiols. Such polyethers are sold by the company Huntsman under the name Jeffamine® or Elastamine® (for example Jeffamine® D400, D2000, ED 2003, XTJ 542).

A two-step method for the preparation of PEBA having ester bonds between the PA blocks and the PE blocks is described in the document FR 2846332 A1. A method for preparing PEBA having amide bonds between the PA blocks and the PE blocks is described in document EP 1482011 A1. The polyether blocks can also be mixed with polyamide precursors and a diacid chain limiter to prepare PEBAs by a one-step process.

If the PEBAs generally comprise a polyamide block and a polyether block, they can also comprise two, three, four or even more different blocks chosen from those described.

The number-average molar masses (Mn) in the present invention are fixed by the content of chain limiter. They can be calculated according to the relationship:

M_not= n_monomerxM_{w repeat pattern}/ not_{chain limiter}+M_{w chain limiter}

In this formula, n_monomerrepresents the number of moles of monomer, n_{chain limiter}represents the number of excess moles of limiter (e.g. diacid), M_{w repeat pattern}represents the molar mass of the repeating unit, and M_{w chain limiter}represents the molar mass of the limiter (eg diacid) in excess.

According to one embodiment, the mass proportion of polyether blocks in the copolymer is at least 50% relative to the total weight of the copolymer.

Preferably, the mass proportion of polyether blocks is from 55 to 85% relative to the total weight of the copolymer, and more preferably from 60 to 80% relative to the total weight of the copolymer.

The mass proportions of blocks in the copolymer can be determined from the number-average molar masses of the blocks.

Copolymer with polyester blocks and polyether blocks (COPE)

According to another embodiment, the thermoplastic elastomer is a copolyetherester (COPE).

The COPEs comprise at least one polyether (PE) block, and at least one PES (homopolyester or copolyester) polyester block.

COPEs include soft PE blocks derived from polyetherdiols and rigid polyester blocks that result from the reaction of at least one dicarboxylic acid with at least one short diol. The PES blocks and the PE blocks are linked by ester bonds resulting from the reaction of the acid functions of the dicarboxylic acid with the OH functions of the polyetherdiol.

The sequence of polyethers and diacids forms the flexible blocks while the sequence of the short diol with the diacids forms the rigid blocks of the copolyetherester.

Advantageously, the diacids are aromatic dicarboxylic acids having from 8 to 14 carbon atoms. Up to 50 mole % of the aromatic dicarboxylic acid may be replaced by at least one other aromatic dicarboxylic acid having 8 to 14 carbon atoms, and/or up to 20 mole % may be replaced by a dicarboxylic acid aliphatic having 2 to 14 carbon atoms. As examples of aromatic dicarboxylic acids, mention may be made of terephthalic acid, isophthalic acid, bibenzoic acid, naphthalene dicarboxylic acid, 4,4'-diphenylenedicarboxylic acid, bis( p-carboxyphenyl) methane, ethylene bis p-benzoic acid, 1-4 tetramethylene bis(p-oxybenzoic acid), ethylene bis(p-oxybenzoic acid), 1,3-trimethylene bis( p-oxybenzoic).

The short diol may in particular be an aliphatic glycol of formula HO(CH ₂ ) _n OH in which n is an integer ranging from 2 to 10, in particular ethylene glycol, 1,3-trimethylene glycol, 1,4- tetramethylene glycol, 1,6-hexamethylene glycol, 1,3 propylene glycol, 1,8 octamethylene glycol and 1,10-decamethylene glycol, or even neopentyl glycol.

The preferred PES units are derived from the reaction of an aromatic dicarboxylic acid, in particular terephthalic acid, with a glycol, in particular ethanediol or 1,4-butanediol. Such copolyetheresters are described in patents EP 402883 A1 and EP 405227 A1.

The PE units can be derived from polyetherdiols as defined above, for example polyethylene glycol (PEG), polypropylene glycol (PPG), polytrimethylene glycol (PO3G) or polytetramethylene glycol (PTMG). The PES units can result from the reaction of a dicarboxylic acid such as terephthalic acid with a glycol such as in particular ethane diol or 1,4-butanediol. Such copolyetheresters are described in patents EP 402883 A1 and EP 405227 A1.

The number-average molar mass (Mn) of the polyester blocks is preferably from 400 to 1500 g/mol, more preferably from 500 to 1200 g/mol, preferably from 500 to 1000 g/mol. For example, the number average molar mass (Mn) of the polyester blocks can be from 400 to 600 g/mol, or from 600 to 900 g/mol, or from 900 to 1000 g/mol, or from 1000 to 1200 g/ mol, or from 1200 to 1300 g/mol, or from 1300 to 1400 g/mol, or from 1400 to 1500 g/mol.

The number-average molar mass (Mn) of the polyether blocks is as described above for the PEBAs.

The mass ratio of the polyester blocks relative to the polyether blocks of the COPE may in particular be from 0.1 to 20. The mass ratio may in particular be from 0.1 to 0.2; or from 0.2 to 0.3; or from 0.3 to 0.4; or from 0.4 to 0.5; or 0.5 to 1; or from 1 to 2; or from 2 to 3; or from 3 to 4; or from 4 to 5; or from 5 to 7; or from 7 to 10; or from 10 to 13; or from 13 to 16; or from 16 to 19; or from 19 to 20. A weight ratio of 2 to 19, and more specifically from 4 to 10 is particularly preferred.

Thermoplastic Polyurethane (TPU)

According to another embodiment, the thermoplastic elastomer is a TPU, i.e. a copolymer with polyurethane (PU) blocks and polyether (PE) blocks, also called polyetherurethane, or a copolymer with polyurethane (PU) blocks and polyester (PES) blocks. , also called polyesterurethane.

The TPUs of the first type mentioned above result from the condensation of polyetherdiols with polyurethanes. The rigid PU blocks and the flexible PE blocks are linked by bonds resulting from the reaction of the isocyanate functions of the polyurethane with the -OH functions of the polyetherdiol.

The PU blocks can result from the reaction of at least one diisocyanate which can be chosen from aromatic diisocyanates (eg: MDI, TDI) and/or aliphatic diisocyanates (eg: HDI or hexamethylenediisocyanate) with at least one short diol. This short diol can be chosen from the glycols mentioned above in the description of the copolyetheresters, in particular polyethylene glycol (PEG), poly(1,2-propylene glycol) (PPG), poly(1,3-propylene glycol) ( PO3G), or polytetramethylene glycol (PTMG).

The TPUs of the second type mentioned above result from the condensation of flexible polyesters with polyisocyanates. The rigid PU blocks and the flexible PES blocks are connected by bonds resulting from the reaction of the isocyanate functions of the polyurethane with the terminal functions of the polyester.

The blocks PU can be as described previously for the TPUs of the first type. Soft PES blocks can be derived from the reaction of an aliphatic dicarboxylic acid having 4 to 12 carbon atoms, in particular adipic acid, with a glycol, such as ethanediol or 1,4-butanediol. Such copolyetheresters are described in patents EP 402883 A1 and EP 405227 A1.

The number-average molar mass (Mn) of the PU blocks in the TPUs is preferably from 400 to 1500 g/mol, more preferably from 500 to 1200 g/mol, preferably from 500 to 1000 g/mol. For example, the number average molar mass (Mn) of the PU blocks can be 400 to 600 g/mol, or 600 to 900 g/mol, or 900 to 1000 g/mol, or 1000 to 1200 g/ mol, or from 1200 to 1300 g/mol, or from 1300 to 1400 g/mol, or from 1400 to 1500 g/mol. That of the polyether blocks is as described above for the PEBAs.

The mass ratio of the polyurethane blocks relative to the polyether blocks of the TPU may in particular be from 0.1 to 20. In particular, it may be from 0.1 to 0.2; or from 0.2 to 0.3; or from 0.3 to 0.4; or from 0.4 to 0.5; or 0.5 to 1; or from 1 to 2; or from 2 to 3; or from 3 to 4; or from 4 to 5; or from 5 to 7; or from 7 to 10; or from 10 to 13; or from 13 to 16; or from 16 to 19; or from 19 to 20. A weight ratio of 2 to 19, and more specifically from 4 to 10 is particularly preferred.

The thermoplastic elastomers according to the invention can be obtained at least partially from bio-resourced raw materials.

By raw materials of renewable origin or bio-resourced raw materials, we mean materials which comprise bio-resourced carbon or carbon of renewable origin. In fact, unlike materials derived from fossil materials, materials composed of renewable raw materials contain ¹⁴ C. The "carbon content of renewable origin" or "bio-resourced carbon content" is determined in application of the standards ASTM D 6866 (ASTM D 6866-06) and ASTM D 7026 (ASTM D 7026-04). By way of example, PEBAs comprising PA 11 blocks come at least in part from bio-resourced raw materials and have a bio-resourced carbon content of at least 1%, which corresponds to an isotopic ratio of ¹² C / ¹⁴ C of at least 1.2 x 10 ^{- 14} . Preferably, the PEBAs comprise at least 50% by mass of bio-resourced carbon over the total mass of carbon, which corresponds to a ¹² C/ ¹⁴ C isotopic ratio of at least 0.6×10 ⁻¹² . This content is advantageously higher, in particular up to 100%, which corresponds to a ¹² C/ ¹⁴ C isotopic ratio of 1.2 x 10 ^-12 , in the case for example of PEBA with PA 11 blocks and PE blocks comprising PTMG from raw materials of renewable origin.

Fillers and reinforcements (b)

The polymer powder according to the invention may also optionally comprise fillers or reinforcements, in particular in order to ensure that the printed article has sufficient mechanical properties, in particular in terms of modulus. These fillers may in particular be carbonated minerals, in particular calcium carbonate, magnesium carbonate, dolomite, calcite, barium sulphate, calcium sulphate, dolomite, alumina hydrate, wollastonite, montmorillonite, zeolite, perlite, nanofillers (fillers having a dimension of the order of a nanometer) such as nano-clays, calcium silicates, magnesium silicates, such as talc, mica, kaolin, I attapulgite and mixtures thereof. As reinforcements, mention may in particular be made of carbon nanotubes, glass fibers and carbon fibers as well as glass beads optionally coated with silane. Component (c) may include one or more fillers and/or reinforcements. Advantageously, the fillers and reinforcements do not include pigments as defined below for the pigment composition.

More specifically, the powder of the invention can comprise 0 to 60%; or from 5 to 50%; or 10 to 40%; or from 10 to 30% by weight of component (c). According to one embodiment, the polymer powder is devoid of fillers and reinforcements.

Additives (c)

The polymer powder may include, where appropriate, additives customary in polymer powders used in 3D printing by sintering.

These may in particular be additives, in powder form or not, which contribute to improving the behavior of the powder in 3D printing by sintering and those which make it possible to improve the properties of the printed articles, in particular the mechanical properties, and including elongation at break and impact resistance.

These usual additives can in particular be chosen from flow agents, fire retardants, flame retardants, anti-UV agents, antioxidants, anti-abrasion agents, light stabilizers, impact modifiers, antistatic agents, pigments and waxes. .

By way of example, the flow agent may for example be chosen from silicas, in particular hydrophobic fumed silica, such as the product marketed under the name Cab-o-Sil® TS610 by Cabot Corporation, precipitated silica, hydrated silica, vitreous silica, fumed silica, vitreous oxides, in particular vitreous phosphates, vitreous borates, alumina, such as amorphous alumina.

The antioxidant agent may comprise a phenolic compound, such as 3,3'-Bis(3,5-di-tert-butyl-4-hydroxyphenyl)-N,N'-hexamethylenedipropionamide marketed in particular under the name Palmarole® AO.OH.98 by Palmarole, (4,4'-Butylidenebis(2-t-butyl-5-methylphenol) marketed in particular under the name Lowinox® 44B25 by Addivant, Pentaerythritol tetrakis(3-(3,5-di -tertbutyl-4-hydroxyphenyl)propionate) marketed in particular under the name Irganox® 1010 by BASF, N,N'-hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide )) marketed in particular 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 marketed in particular under the name Irganox® 1330 by BASF, Ethylenebis(oxyethylene)bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate) marketed in particular 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 marketed in particular under the name Irganox® 3114 by BASF, N'N'-(2-ethyl-2'ethoxyphenyl)oxanilide marketed in particular under the name Tinuvin® 312 by BASF, Phenol 4,4',4"-trimethyl-1,3, 5-benzenetriyl) tris-(methylene)] tris 2,6-bis(1,1-dimethylethyl) marketed in particular under the name Alvinox® 1330 by 3V, Hostanox® 245 FF, Hostanox® 245 Pwd, marketed by Clariant, Pentaerythritol Tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) marketed in particular under the names Evernox® 10, Evernox® 10GF, by Everspring Chemical Company Limited, Octadecyl-3-(3,5 -di-tert-4-hydroxyphenyl)-propionate marketed in particular under the names Evernox® 76, Evernox® 76GF by Everspring Chemical Company Limited, Tetrakis [Methylene-3 (3′,5′-di-tert-butyl-4- hydroxyphenyl) propionate] methane marketed in particular under the name BNX® 1010 by Mayzo, Thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] marketed in particular under the name BNX® 1035 by Mayzo, the Tetrakis [Methylene-3 (3',5'-di -tert-butyl-4-hydroxyphenyl)propionate] methane, Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate marketed in particular under the name BNX® 2086 by Mayzo, on 1.3, 5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)trione marketed in particular under the name BNX® 3114 by Mayzo .

The antioxidant can also comprise a phosphate compound, such as the Hostanox® P-EPQ® product marketed by Clariant.

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

The wax can comprise a wax of polyethylene and polypropylene, polytetrafluoroethylene, ketones, acid, partially esterified acid, acid anhydride, ester, aldehydes, amides, their derivatives as well than their mixtures. The wax may in particular comprise a product marketed under the name Crayvallac® WN1135, WN 1495 or WN1265 by ARKEMA or a product marketed under the name Ceridust® ^9615A or 8020 marketed by CLARIANT.

According to a particular embodiment, the wax is present in the powder in the form of a coating covering at least partially the polymer composition.

Polymer powder

The powder according to the invention comprises a polymer composition (a) comprising at least one thermoplastic polymer, preferably a thermoplastic elastomer, and optionally fillers or reinforcements (component (b)) and/or one or more additives (component (c )).

According to one embodiment, the powder according to the invention comprises:
(a) 30 to 99%, preferably 40 to 95%, especially 50 to 90% and most preferably 70 to 85% by weight of a thermoplastic polymer composition;
(b) 0 to 70%, preferably 10 to 50%, and in particular 20 to 30% by weight of one or more fillers or reinforcements; And
(c) 0 to 10%, preferably 0.1 to 7.5%, in particular 1 to 5% by weight of one or more additives,
the respective proportions of components (a), (b) and (c) adding up to 100%.

According to one embodiment, the polymer composition (a) comprises at least one thermoplastic elastomer as described above.

The powder according to the invention, to be suitable for 3D printing by sintering, will have a suitable particle size distribution.

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

The polymer powder according to the invention can have a Tm of 100 to 300°C, and preferably of 120 to 200°C.

The powder may have a Tc of 40 to 250°C, and preferably 45 to 200°C, for example 45 to 150°C.

When composition (a) comprises several polymers, we consider as Tf, the lowest Tf in the mixture, and as Tc, the highest Tc in the mixture.

The difference between the Tc and the Tf of the powder is preferably greater than or equal to 20°C, or more preferably greater than or equal to 30°C.

Powder preparation process

The polymer powder can be manufactured according to the usual methods.

The polymer compositions useful in the present invention are commercially available, in particular in the form of granules, flakes or powder. If necessary, component (a) can be transformed into powder, by means of known methods, in particular by grinding.

Preferably, the grinding is cryogenic grinding. In this process, the material to be ground is cooled below the thermoplastic polymer glass transition temperature, for example by means of liquid nitrogen, liquid carbon dioxide or liquid helium. The grinding can be carried out, for example, in a counter-rotating pin mill (pin mill), a hammer mill (hammer mill) or in a whirl mill (whirl mill).

The grinding can be carried out before and/or after bringing the polymer into contact with the various additives, namely the components (b), and (c).

Components (b) and (c) are mostly available in powder form.

One or more additives (component (c)) can be added to the polymer composition (component (a)) before grinding, in particular by adding one or more additives to the polymer in fusion, for example in an extruder ( compounding).

As an alternative or in addition, one or more additives and the fillers and reinforcements can be added after grinding, for example by dry addition (dry blend). Furthermore, it is possible to mix the components by means of a co-precipitation of the polymer composition from a solution in the presence of the component(s) (dissolution/precipitation).

The powder thus obtained can then be sieved or subjected to a selection step to obtain the desired particle size profile.

Before use, the polymer powder can then, if necessary, be subjected to different treatments, in particular thermal or hydraulic treatments, so that it is better suited to 3D printing by sintering.

Powder sintering process

The polymer powder as described above is useful in particular for being implemented in a 3D printing process by sintering. The powder of the invention can be used in a selective laser sintering process (SLS, Selective Laser Sintering, in English), a sintering process of the MJF (Multi Jet Fusion) type or a sintering process of the HSS (High speed sintering).

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

In this type of process, a thin layer of powder is deposited on a horizontal plate held in an enclosure heated to a temperature called the construction temperature. The build temperature refers to the temperature to which the powder bed, of a constituent layer of a three-dimensional article under construction, is heated during the layer-by-layer sintering process of the powder. Electromagnetic radiation, for example in the form of a laser, then provides the energy needed to sinter the powder particles at different points of the powder layer according to a geometry corresponding to an object, for example using a computer having in memory the shape of an object and restoring the latter in the form of slices. Then, the horizontal plate is lowered by a height corresponding to the thickness of a layer of powder, and a new layer of powder is spread, heated and then sintered in the same way. The process is repeated until the object is made.

The layer of powder deposited on a horizontal plate can have, before sintering, for example a thickness of 50 to 300 μm, and preferably of 80 to 220 μm. After sintering, the thickness of the layer of agglomerated material is a little lower, and may for example have a thickness of 20 to 200 μm, and preferably of 30 to 150 μm.

For the MJF and HSS process, the entire layer of building material is exposed to radiation, but only a part covered with a melting agent is melted to become a layer of a 3D part. The fusion agent is applied selectively to the selected region of the building material. The melting agent is able to penetrate the layer of the building material and transmits the absorbed energy to the neighboring building material, thereby causing it to melt or be sintered. By melting, bonding and subsequent hardening of each layer of the building material, the object is formed.

Advantageously, the use of the polymer powder of the invention in these processes does not require any particular modification of the equipment.

The powder composition according to the invention makes it possible to manufacture printed parts of good quality, having good mechanical properties and precise and well-defined dimensions and contours.

The polymer powder according to the invention can be recycled and reused in several successive constructions. It can for example be used as it is or mixed with other powders, whether recycled or not.

The following examples illustrate the invention without limiting it.

EXAMPLE

Each polymer used (with the exception of example C) was obtained by grinding the corresponding granules in a cryogenic mill with contra-rotating spindles.

A polymer powder is obtained having a particle size distribution measured according to the ISO 13320 standard, characterized by a Dv10 of 30 μm, a Dv50 of 90 μm and a Dv90 of 175 μm.

In a Henschel IAM 6L mixer, the polymer powder prepared with various additives is introduced by dry mixing.

The different powders have been presented below.

Example
Polymer composition

Hydrophobic fumed silica

Amide wax Tm (°C) AT
(comparative) 97.7%
PA12-PTMG
1000g/mol-1000g/mol 0.3% 2.0% 147 B
(comparative) 97.7%
PA11-PTMG
1000g/mol-1000g/mol 0.3% 2.0% 157 B'
(comparative) 97%
PA11-PTMG
1000g/mol-1000g/mol 1.0% 2.0% 157 VS
(comparative) A thermoplastic polyurethane powder, marketed under the name Ultrasint® TPU 88A (BASF) at 100% 168 D 97.7%
PA11/12 (mass concentration 90%/10%) -PTMG 1000 g/mol – 1000 g/mol 0.3% 2.0% 149 E 97.7%
PA11/12 (mass concentration 70%/30%) -PTMG 1000 g/mol – 1000 g/mol 0.3% 2.0% 134 E' 97%
PA11/12 (mass concentration 70%/30%) -PTMG 1000 g/mol – 1000 g/mol 1.0% 2.0% 134 F 97.7%
PA11-PTMG
650g/mol - 650g/mol 0.3% 2.0% 144

The polymer powder thus obtained is then used to print by laser sintering a 1B XY specimen according to the ISO 527-1B standard on a Prodways P1000 machine at a powder bed temperature equal to Tf - 30°C by 3D printing by laser sintering .

The laser conditions used are the same for all prints.

During construction, the temperature of the powder on the surface of the construction tank is imposed, and measured on the surface by means of an infrared thermal sensor.

The specimens thus obtained are then characterized in terms of their mechanical properties. More specifically, the elongation at break of the specimens is measured on an INSTRON 5966 machine according to the ISO 527-2 standard. The elongation at break indicated corresponds to the average of the elongation at break through measured for 5 printed 1B XY specimens.

Examples G"1 (Pa) G"2 (Pa) G"2/ G"1 Elongation at break in XY (%)
3D Elongation at break in XY (%)
Injection A (comparative) 19159 57604 3.01 300
>400 B
(comparative) 11362 34254 3.01 240
>400 B' (comparative) 11362 34254 3.01 240
>400 VS
(comparative) 1820 5933 3.26 270
>400 D 27826 72469 2.60 >400 >400 E 54210 126659 2.34 >400 >400 E' 54210 126659 2.34 >400 >400 F 13411 37520 2.80 >400 >400

It can be seen in the table that powders with a G"2/G"1 value of less than 3.00 have a better result in the elongation at break test in XY, comparable with the results obtained on the prepared parts, at From the same powder, by injection under standard injection molding conditions of ISO 527 - 1B specimens, all these parts have elongations at break greater than 400%.

Claims (18)

Polymer powder suitable for 3D printing by sintering, comprising:
(a) a thermoplastic polymer composition; and optionally,
(b) one or more fillers or reinforcements,
(c) one or more additives,
where the G"2/G"1 ratio of said powder is less than or equal to 3.00, preferably less than or equal to 2.90,
G"1 being the loss modulus at the melting temperature (Tf) of the powder, when the powder is heated to Tm+40°C for 2 minutes and is then cooled down to Tm at a rate of -5° c/min,
G"2 being the loss modulus at - 30°C of the Tf of the powder, when the powder is heated to Tf+ 40°C for 2 minutes and is then cooled down to Tf-30°C at a rate of -5°C/min,,
the values of G"2, G"1 being measured according to standard ISO 6721-10: part 10, at an angular frequency of 6.28 rad/sec. Powder according to Claim 1, in which the ratio G"2/G"1 is less than or equal to 2.80. Powder according to Claim 1 or 2, having a G"1 less than or equal to 100,000 Pa, preferably less than or equal to 50,000 Pa. Powder according to one of Claims 1 to 3, in which the polymer composition (a) has an enthalpy of fusion less than or equal to 60 J/g, preferably less than or equal to 55 J/g. Powder according to one of Claims 1 to 4, in which the polymer composition (a) comprises at least one thermoplastic polymer chosen from polypropylene (PP), polyolefin, polyamide (PA), polyester, polyarylether ketone (PAEK), polyphenylene, polyacetal, polyimide, vinylidene fluoride polymer and/or their mixture, preferably chosen from PP, PA, and/or PAEK. Powder according to Claim 5, in which the polymer composition (a) comprises a polyaryl ether ketone (PAEK), chosen from poly-ether-ketone-ketone (PEKK), poly-ether-ether-ketone (PEEK), poly-ether -ketone (PEK), poly-ether-ether-ketone-ketone (PEEKK), poly-ether-ether-ether-ketone (PEEK), poly-ether-diphenyl-ether-ketone (PEDEK), mixtures thereof and/ or their copolymers. Powder according to one of Claims 1 to 4, in which the polymer composition (a) comprises a thermoplastic elastomer chosen from the group consisting of block copolymers SBS, SIS, SEBS, TPU, COPE and PEBA as well as their mixtures and alloys . A powder according to claim 7, wherein the polymer composition (a) comprises a PEBA. Powder according to claim 7 or 8, in which the polyamide blocks of the PEBA are copolyamide blocks, preferably chosen from the blocks PA 6/11, PA 6/12, PA 11/12, PA 6/11/12, PA 6 /66/12, PA 6/1010, PA 6/1012, PA 6/1010/1012, PA 6/1012/12, PA 6/66/11/12, PA 6/1010/1012/1014, as well as their mixtures. Powder according to Claim 9, in which one of the monomers constituting the copolyamide represents more than 50%, preferably more than 60% by mass of the total mixture of monomers and/or less than 90%, preferably less than 80% by mass of the total monomer mixture. Powder according to Claim 7 or 8, in which the polyamide blocks in the PEBA result from the condensation of an α,ω-aminocarboxylic acid or of a lactam and the number-average molar mass (Mn) of the polyamide blocks in the PEBA is preferably from 400 to 1500 g/mol, more preferentially from 500 to 1200 g/mol, preferentially from 500 to 1000 g/mol. Powder according to Claim 7, in which the number-average molar mass (Mn) of the polyester blocks in the COPE is from 400 to 1500 g/mol, more preferably from 500 to 1200 g/mol. Powder according to Claim 7, in which the number-average molar mass (Mn) of the PU blocks in the TPU is from 400 to 1500 g/mol, more preferably from 500 to 1200 g/mol. Powder according to Claim 1, having a diameter Dv50 as measured according to standard ISO 9276 - parts 1 to 6, of 40 to 150 µm. Powder according to claim 1, comprising:
(a) 30 to 99% by weight of a thermoplastic polymer composition;
(b) 0 to 70% by weight of one or more fillers or reinforcements; And
(c) 0 to 10% by weight of one or more additives,
the respective proportions of components (a), (b) and (c) adding up to 100%. Process for preparing a powder according to one of Claims 1 to 15, comprising the steps of:
(i) grinding a polymer composition (a) into a powder with a volume average diameter Dv50 of 40 to 150 µm, before or after,
(ii) introduction of at least one or more fillers or reinforcements and/one or more additives, where appropriate. Use of a powder according to one of claims 1 to 15 for 3D printing by sintering, preferably chosen from the selective laser sintering process (SLS), the MJF (Multi Jet Fusion) type sintering process and the HSS (High Speed Sintering) type sintering process. Article obtained by 3D printing by sintering a powder as defined in claims 1 to 15.