EP4041529A1 - Thermoplastic polymer composition for constructing 3d articles - Google Patents

Abstract

The invention relates to a composition for constructing a three-dimensional article layer by layer, by sintering of the composition caused by electromagnetic radiation, the composition comprising a semi-crystalline thermoplastic polymer powder and at least one wax, the wax having a melting point greater than the crystallisation temperature of the semi-crystalline thermoplastic polymer, the composition further optionally comprising a flow agent. The invention also relates to a method for preparing the composition and its use for constructing a three-dimensional article layer by layer.

Description

Thermoplastic polymer composition for construction of 3D articles

FIELD OF THE INVENTION

The present invention relates to a composition for the manufacture of a three-dimensional (3D) article layer by layer, by sintering, caused by electromagnetic radiation. More particularly, the present invention relates to a composition comprising a powder of semi-crystalline thermoplastic polymer and a wax, and its method of preparation. The invention also relates to the use of this composition and to articles made from it.

TECHNICAL BACKGROUND

The construction of 3D articles is often used to produce prototypes, models of parts ("rapid prototyping") or to produce finished parts in small series ("rapid manufacturing"), for example in the fields: automotive, nautical, aeronautics, aerospace, medical (prostheses, hearing systems, cellular tissues ...), textiles, clothing, fashion, decoration, housings for electronics, telephony, home automation, IT, lighting, sport, industrial tools.

Among the manufacturing techniques of 3D articles, the manufacturing process by sintering is particularly interesting. According to this method, a layer of polymer powder is selectively and briefly irradiated in a chamber by electromagnetic radiation (eg laser beam, infrared radiation, UV radiation), the result being that the powder particles impacted by the radiation melt. The molten particles coalesce and solidify to form a solid mass. This process can easily produce 3D articles by repeatedly irradiating a succession of freshly applied powder layers.

The quality of the manufactured parts as well as their mechanical properties depend on the characteristics of the polymer powder. Thermoplastic polymers are appreciated for being used for restrictive temperature and / or mechanical, or even chemical, applications. Thermoplastic elastomeric polymers have proven to be particularly interesting: they combine mechanical properties with very good resistance to thermal or UV aging, as well as low density, which thus allow the production of light and flexible parts.

However, these thermoplastic polymer powders must be adapted to be used in sintering devices.

For example, the powder must be able to be conveyed and form a uniform bed, without clumping or forming clusters or crevices.

The addition of an additive such as a flow agent can improve flow properties to some extent.

To achieve sintering, it is known to maintain the powder bed at a temperature within a working window, between the crystallization temperature (Te) and the melting temperature (Tf) of the powder to ensure good cohesion between the layers of the object during manufacture and avoid deformation phenomena. It is therefore preferable to use a polymer whose difference between Tm and Te is as large as possible, to widen the working window, and thus make its use in a sintering process easier.

By “working window” is meant the temperature range of the powder bed at which sintering is actually possible.

However, it has been observed that for some powder compositions based on semi-crystalline thermoplastic polymer, sintering is not always possible even if the Tm-Tc difference of the polymer is sufficiently large. The working window can be narrow (e.g. less than 5 ° C) or none.

There is therefore a need to provide a composition based on thermoplastic polymer powder, in particular on elastomeric thermoplastic polymer, which makes it possible to manufacture articles of good quality, having good mechanical properties and precise and well-defined dimensions and contours, in particular. by making it possible to work with a larger working window, and to implement the method more easily.

Furthermore, powder bed cohesion problems have been observed during sintering. More specifically, the parts being manufactured can sink inside the powder bed and come up on its edges, which prevents the completion of their manufacture. It is therefore sought to provide a powder composition which makes it possible to reinforce the cohesion of the bed in order to prevent the parts from sinking into the powder bed during sintering.

There is also a need to provide such a thermoplastic polymer powder composition having good recyclability.

The present invention makes it possible to meet the needs expressed above.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention relates to a composition for the construction of a three-dimensional (3D) article layer by layer, by sintering of the composition, caused by electromagnetic radiation, the composition comprising:

a powder of semi-crystalline thermoplastic polymer;

a wax, the wax having a dropping point higher than the crystallization temperature (Te) of the semi-crystalline thermoplastic polymer;

- and optionally a flow agent.

According to a particularly interesting embodiment, the semi-crystalline thermoplastic polymer (TP sc) is an elastomer.

The composition of the present invention makes it possible to construct 3D articles having good definition and homogeneity over the whole of the part concerning its physical, mechanical and even chemical properties.

According to one embodiment of the invention, the TP sc polymer is chosen from:

- a polyamide,

- a homopolymer or copolymer of vinylidene fluoride (PVDF),

- a copolymer with polyamide blocks and polyether blocks (PEBA),

- a thermoplastic polyurethane (TPU),

- a copolymer with polyester blocks and polyether blocks (COPE), and

- their mixtures.

Preferably, the TP sc polymer is an elastomer, chosen from:

- a PEBA,

- a TPU, - a COPE, and

- their mixtures.

The wax can be chosen in particular from polyolefin waxes, waxes of plant or animal origin as well as mixtures thereof, for example, the wax can be chosen from polyethylene and polypropylene waxes, polytetrafluoroethylene waxes, waxes of ketones, acid waxes, partially esterified acid waxes, acid anhydride waxes, ester waxes, aldehyde waxes, amide waxes, their derivatives and mixtures thereof.

The invention also relates to a process for preparing the composition described above comprising:

- the supply of a TP sc polymer, preferably in powder form, and

- bringing the TP sc polymer into contact with a wax and optionally the flow agent.

According to one embodiment, the placing of the TP sc polymer into contact with the wax is carried out by dry mixing.

According to one embodiment, the TP sc polymer is brought into contact with the wax:

- dissolving the wax in an appropriate solvent to form a wax solution;

- by mixing said wax solution with the TP sc polymer to form a dispersion; and

- By removing the solvent from said dispersion, for example by evaporation, to obtain the TP sc polymer coated with wax.

The invention also relates to the use of the composition described above, for the construction of a layer-by-layer 3D article, by sintering of the composition caused by electromagnetic radiation, preferably by laser radiation.

The invention also relates to a 3D article made from the composition described above, preferably by layer-by-layer construction by sintering caused by electromagnetic radiation, preferably by laser radiation. In the context of the present invention, it has been observed that the use of wax in the composition increases the width of the working window with respect to the same composition without wax and thus makes it possible to carry out manufacturing by sintering with a wide choice of TP sc polymer-based compositions, even those with a narrow or no working window.

This is of particular interest in the case where the composition further comprises a flow agent.

Furthermore, it has been observed that the use of wax makes it possible to increase the cohesion of the powder bed during sintering, and thus to prevent the manufactured parts from sinking inside the powder bed and distort. This constitutes another advantage of the present invention.

Thus, according to another aspect, the invention relates to the use of a wax to increase the cohesion of the bed of TP sc polymer powder in a sintering process by electromagnetic radiation, preferably by laser radiation.

The composition according to the invention further exhibits good recyclability.

Without wishing to be bound by any particular theory, it seems that the wax, at the temperature of the powder bed, adheres to the polymer particles, which allows the cohesion of the powder bed to be increased; once the sintering has been carried out, and when the temperature of the powder bed decreases, the wax stiffens and peels off from the unsintered polymer particles, which makes it possible to recycle and reuse them.

In one aspect, the invention relates to the use of a particular wax in a powder composition based on the TP sc polymer to improve the recyclability of powders in a construction of 3D articles by sintering.

According to another aspect, the invention relates to a method of constructing articles by sintering using a composition as described above where the method comprises a step of recycling the unsintered powders.

According to one embodiment, the composition is reused in several successive constructions.

According to yet another aspect, the invention relates to the 3D article obtained from a composition comprising recycled TP sc polymer powders. Semi-crystalline thermoplastic polymer

The thermoplastic polymer according to the invention is semi-crystalline. The term “semi-crystalline thermoplastic polymer” means a thermoplastic polymer which has:

- a crystallization temperature (Te) determined according to ISO 11357-3: 2013, during the cooling step at a speed of 20K / min in DSC (differential scanning calorimetry or "differential scanning calorimetry");

- a melting temperature (Tf) determined according to the ISO 11357-3: 2013 standard during the heating step at a speed of 20 K / min in DSC; and

- and an enthalpy of fusion (AHf) determined according to standard ISO 11357-3: 2013 during the heating step at a speed of 20 K / min in DSC, which is greater than 5 J / g, preferably greater than 10 J / g, for example greater than 20 J / g and is generally less than 200 J / g, preferably less than 150 J / g, for example less than 100 J / g, or less than 50 J / g.

The semi-crystalline thermoplastic polymer of the invention can have a Tm of 100 to 300 ° C, and preferably 120 to 200 ° C. This Tf corresponds to the first heating. The TP sc polymer can have a Te of 40 to 250 ° C, and preferably from 45 to 200 ⁰ C, for example from 45 to 150 ⁰ C.

Typically, the Tf and Te are determined directly from the TP sc powder.

When it is a polymer blend, we consider Tf, the lowest Tf in the polymer blend, and Te, the highest Te in the polymer blend.

The difference between the Te and the Tf of the TP sc polymer is preferably greater than or equal to 20 ° C, preferably greater than or equal to 30 ° C, preferably greater than or equal to 40 ° C, or to 50 ° C. , or at 60 ° C, or at 70 ° C, or at 0 ° C.

The TP sc polymer of the invention can in particular be chosen from polyamides, PVDF, PEBA, TPU, COPE and mixtures thereof.

Polyamide

According to one embodiment, the semi-crystalline thermoplastic polymer is a semi-crystalline polyamide (PA sc). It may be a homopolyamide or a copolyamide, or else a mixture of these. Thus, the polyamide according to the invention can be obtained by the polymerization of a monomer (homopolyamide) or of at least two different monomers (copolyamide) chosen from:

- monomers of amino acid or aminocarboxylic acid type, and preferably α, w-aminocarboxylic acids;

- lactam-type monomers having from 3 to 18 carbon atoms on the main cycle and which may be substituted;

- monomers of the “diamine.diacid” type resulting from the reaction between an aliphatic diamine having from 4 to 36 carbon atoms, preferably from 4 to 18 carbon atoms and a dicarboxylic acid having from 4 to 36 carbon atoms, of preferably from 4 to 18 carbon atoms; and

their mixtures, with monomers with a different carbon number in the case of mixtures between a monomer of amino acid type and a monomer of lactam type.

The term "monomer" in this description should be taken in the sense of "repeating unit". Indeed, the case where a repeating unit of the polyamide (PA) consists of the association of a diacid with a diamine is particular. It is considered that it is the combination of a diamine and a diacid, that is to say the diamine.diacid couple (in equimolar quantity), which corresponds to the monomer. This is because, individually, the diacid or diamine is only a structural unit, which is not sufficient on its own to polymerize.

Regarding amino acid type monomers, as examples of a, o> amino acids, mention may be made of those having from 4 to 18 carbon atoms, such as aminocaproic, 7-aminoheptanoic, 11-aminoundecanoic, N-heptyl acids. -11- aminoundecanoic and 12-aminododecanoic.

As regards lactam-type monomers, by way of examples, mention may be made of those having from 3 to 18 carbon atoms on the main cycle and which may be substituted. Mention may be made, for example, of b, b-dimethylpropriolactam, a, a-dimethylpropriolactam, amylolactam, caprolactam also called lactam 6, capryllactam also called lactam 8, oenantholactam and lauryllactam also called lactam 12.

Regarding monomers of the “diamine.diacid” type:

As examples of dicarboxylic acid, mention may be made of acids having from 4 to 36 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 sulphoisophthalic acid, dimerized fatty acids (these dimerized fatty acids have a dimer content of at least 98% and are preferably hydrogenated) and dodecanedioic acid HOOO- (OH) io-OOOH, and tetradecanedioic acid.

The term “dimers of fatty acids or dimerized fatty acids” is understood to mean more particularly the product of the reaction of dimerization of fatty acids (generally containing 18 carbon atoms, often a mixture of oleic and / or linoleic acid). It is preferably a mixture comprising 0 to 15% C18 monoacids, 60 to 99% C36 diacids, and 0.2 to 35% triacids or polyacids C54 or more.

By way of example of a diamine, mention may be made of aliphatic diamines having from 4 to 36 atoms, preferably from 4 to 18 atoms, which may be saturated aryl and / or cyclic. By way of examples, mention may be made of hexamethylenediamine, piperazine (abbreviated as "Pip"), aminoethylenepiperazine, tetramethylene diamine, octamethylene diamine, decamethylene diamine, dodecamethylene diamine, 1, 5 diaminohexane, 2 , 2,4-trimethyl-1,6-diamino-hexane, polyols diamine, isophorone diamine (IPD), methyl pentamethylenediamine (MPMD), bis (aminocyclohexyl) methane (BACM), bis (3-methyl -4 aminocyclohexyl) methane (BMACM), p-bis (aminocyclohexyl) -methane commonly referred to as “PACM”, methaxylyenediamine, and bis-p aminocyclohexylmethane.

As examples of diamines.diacids, mention may be made more particularly of those resulting from the condensation of 1, 6-hexamethylenediamine with a dicarboxylic acid having from 6 to 36 carbon atoms and those resulting from the condensation of 1, 10 -decamethylenediamine with a diacid having from 6 to 36 carbon atoms.

As examples of monomers of the “diamine.diacid” type, mention may be made in particular of the monomers: 66, 610, 611, 612, 614, 618. Mention may be made of the monomers resulting from the condensation of decanediamine with a diacid in C6 to C36, in particular the monomers: 1010, 1012, 1014, 1018. In the numerical notation XY, X represents the number of carbon atoms resulting from the diamine residues, and Y represents the number of carbon atoms resulting from the residues of diacid, in a conventional manner.

The homopolyamide is typically an aliphatic homopolyamide, preferably a linear aliphatic homopolyamide. The copolyamide can be aliphatic, aromatic or semi-aromatic.

According to one embodiment, the PA sc is a semi-aromatic copolyamide, for example of formula X / YAr, as described in EP1505099, in particular of formula A / XT in which A is chosen from a unit obtained from a amino acid, a unit obtained from a lactam and a unit corresponding to the formula (diamine.diacid).

As examples of (co) polyamides, mention may be made of: PA 410, PA 4T, PA 66, PA 46, PA 610, PA 612, PA 11, PA 12, PA 910, PA 912, PA 913, PA 914 , PA 915, PA 916, PA 918, PA 936, PA 1010, PA 1012, PA 1013, PA 1014, PA 1210, PA 1212, PA 1213, PA 1214, PA 614, PA 613, PA 615, PA 616, PA 618, PA MXD6, PA MXD10, PA 12T, PA 10T, PA 9T, PA 18T, PA 6T / 66, PA 66 / 6T / 6I, PA 6 / 6T. XT denotes a unit obtained from the polycondensation of a Cx diamine and terephthalic acid, with x representing the number of carbon atoms of the Cx diamine, x being between 6 and 36, advantageously between 9 and 18, in particular a polyamide of formula A / 6T, A / 9T, A / 10T or A / 11T, A being as defined above, in particular a polyamide chosen from MPMDT / 6T, / 10T, 5T / 10T, 11 / BACT,

11 / 6T / 10T, MXDT / 10T, MPMDT / 10T, BACT / 10T, BACT / 6T, BACT / 10T / 6T,

11 / BACT / 6T, 11 / MPMDT / 6T, 11 / MPMDT / 10T, 11 / BACT / 10T, 11 / MXDT / 10T, and 11 / 5T / 10T, T corresponding to terephthalic acid, MXD corresponding to m - xylylenediamine, MPMD corresponding to methylpentamethylene diamine, and BAC corresponding to bis (aminomethyl) cyclohexane.

According to a preferred embodiment, the polyamide is chosen from polyamide (PA) 11, PA 12 or PA 6.

The homopolyamide or the copolyamide in the context of the invention is a TP sc polymer having a Te, a Tf and an AHf as defined above.

Vinylidene Fluoride Polymer (PVDF)

According to one embodiment, the semi-crystalline thermoplastic polymer is a PVDF. PVDF can be a homopolymer or a copolymer. The term “copolymer” denotes here generically the polymers obtained by polymerization of VDF with at least one other comonomer, ie polymers having repeating units derived from VDF and from at least one other comonomer. Preferably, it is a copolymer in the strict sense, that is to say having repeating units derived from VDF and from a single other comonomer.

Preferably the comonomer (or the comonomers) is 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, Ft _f being an alkyl group, preferably C1 to C4. Preferred examples are PPVE (perfluoropropylvinylether) and PMVE (perfluoromethylvinylether).

PVDF can be obtained by known polymerization methods such as solution, emulsion or suspension polymerization. According to one embodiment, it is prepared by an emulsion polymerization process in the absence of fluorinated surfactant.

PVDF, when it is a copolymer, can be homogeneous or heterogeneous, and preferably homogeneous. A homogeneous copolymer has a uniform chain structure, the statistical distribution of the comonomers not varying between the polymer chains. In a heterogeneous copolymer, the polymer chains have an average comonomer content distribution of multimodal or spread type: it therefore comprises polymer chains rich in a comonomer and polymer chains poor in said comonomer. An example of heterogeneous PVDF appears in document WO 2007/080338. A homogeneous copolymer can be prepared by a one-step process, in which the comonomers are injected gradually while keeping a constant mass ratio between them.

According to a preferred embodiment, the polymer is an elastomeric TP sc polymer chosen from a PEBA copolymer, a TPU or a COPE.

Preferably, the elastomeric thermoplastic has an instantaneous hardness less than or equal to 40 Shore D, more preferably less than or equal to 35 Shore D. The hardness measurements can be carried out according to standard ISO 868: 2003.

Polyamide block and polyether block copolymer (PEBA)

According to one embodiment, the semi-crystalline thermoplastic polymer is a "PEBA" copolymer, it may preferably be a linear (non-crosslinked) copolymer.

PEBAs result from the polycondensation of polyamide blocks with reactive ends with polyether blocks with reactive ends, such as, among others, polycondensation:

1) polyamide blocks having diamine chain ends with polyoxyalkylene blocks containing dicarboxylic chain ends;

2) polyamide blocks containing dicarboxylic chain ends with polyoxyalkylene blocks containing diamine chain ends, obtained for example by cyanoethylation and hydrogenation of aliphatic α, w-dihydroxylated polyoxyalkylene blocks called polyetherdiols;

3) polyamide blocks containing dicarboxylic chain ends with polyetherdiols, the products obtained being, in this particular case, polyetheresteramides.

The polyamide blocks containing dicarboxylic chain ends originate, for example, from the condensation of polyamide precursors in the presence of a dicarboxylic acid chain limiter. The polyamide blocks having diamine chain ends originate, for example, from the condensation of polyamide precursors in the presence of a chain-limiting diamine.

Three types of polyamide blocks can advantageously be used.

According to a first type, the polyamide blocks come from the condensation of a dicarboxylic acid, in particular those having 4 to 20 carbon atoms, preferably those having 6 to 18 carbon atoms, and an aliphatic diamine. or aromatic, in particular those having 2 to 20 carbon atoms, preferably those having 6 to 14 carbon atoms.

As examples of dicarboxylic acids, mention may be made of butanedioic, adipic, azelaic, suberic, sebacic, dodecanedicarboxylic, octadecanedicarboxylic and terephthalic and isophthalic acids, but also dimerized fatty acids.

As examples of diamines, mention may be made of tetramethylene diamine, hexamethylenediamine, 1, 10-decamethylenediamine, dodecamethylenediamine, trimethylhexamethylene diamine.

Advantageously, polyamide blocks PA 412, PA 414, PA 418, PA 610, PA 612, PA 614, PA 618, PA 912, PA 1010, PA 1012, PA 1014 and PA 1018 are used.

In the PA notation XY, X represents the number of carbon atoms resulting from the diamine residues, and Y represents the number of carbon atoms resulting from the diacid residues, in a conventional manner.

According to a second type, the polyamide blocks result from the condensation of one or more α, w-aminocarboxylic acids and / or of one or more lactams having from 6 to 12 carbon atoms. Examples of lactams include caprolactam, enantholactam and lauryllactam. As examples of α, w-amino carboxylic acid, mention may be made of aminocaproic, 7-amino-heptanoic, 11-amino-undecanoic and 12-amino-dodecanoic acids.

Advantageously, the polyamide blocks of the second type are blocks of PA 11 (polyundecanamide), of PA 12 (polydodecanamide) or of PA 6 (polycaprolactam). In PA X notation, X represents the number of carbon atoms resulting from amino acid residues.

The condensation according to this type can be carried out in the presence of a chain limiter, for example, a dicarboxylic acid having 4 to 12 carbon atoms or a diamine.

According to a third type, the polyamide blocks result from the condensation of at least one α, w-aminocarboxylic acid (or one lactam), at least one diamine and at least one dicarboxylic acid.

In this case, the polyamide PA blocks are prepared by polycondensation:

- linear or aromatic aliphatic diamine (s) having X carbon atoms;

- dicarboxylic acid (s) having Y carbon atoms; and

- of the comonomer (s) {Z}, chosen from lactams and α, w-aminocarboxylic acids having Z carbon atoms and equimolar mixtures of at least one diamine having X1 carbon atoms and at least one dicarboxylic acid having Y1 carbon atoms, (X1, Y1) being different from (X, Y),

- said {Z} comonomer (s) being introduced in a proportion by weight advantageously ranging up to 50%, preferably up to 20%, even more advantageously up to 10% relative to all the polyamide precursor monomers;

- in the presence of a chain limiter chosen from dicarboxylic acids. Advantageously, the dicarboxylic acid having Y carbon atoms, which is introduced in excess relative to the stoichiometry of the diamine (s), is used as chain limiter.

According to a variant of this third type, the polyamide blocks result from the condensation of at least two a, w-aminocarboxylic acids or of at least two lactams having from 6 to 12 carbon atoms or of a lactam and a aminocarboxylic acid not having the same number of carbon atoms in the possible presence of a chain limiter.

As examples of aliphatic α, w-aminocarboxylic acid, mention may be made of aminocaproic, 7-amino-heptanoic, 11-amino-undecanoic and 12-aminododecanoic acids.

By way of examples of a lactam, mention may be made of caprolactam, oenantholactam and lauryllactam.

As examples of aliphatic diamines, mention may be made of hexamethylenediamine, dodecamethylenediamine and trimethylhexamethylene diamine.

As examples of aliphatic diacids, mention may be made of butane-dioic, adipic, azelaic, suberic, sebacic, dodecanedicarboxylic and dimerized fatty acids. These dimerized fatty acids preferably have a dimer content of at least 98%; preferably they are hydrogenated; it is for example the products marketed under the brand "PRIPOL®" by the company "CRODA", or under the brand EMPOL® by the company BASF, or under the brand Radiacid® by the company OLEON, and polyoxyalkylenes a, w-diacids.

As examples of aromatic diacids, mention may be made of terephthalic (T) and isophthalic (I) acids.

As examples of polyamide blocks of the third type, the following may be mentioned:

- PA 66/6, where 66 denotes hexamethylenediamine units condensed with adipic acid and 6 denotes units resulting from the condensation of caprolactam;

- PA 66/610/11 / 12, where 66 denotes hexamethylenediamine condensed with adipic acid, 610 denotes hexamethylenediamine condensed with sebacic acid, 11 denotes units resulting from the condensation of aminoundecanoic acid and 12 denotes units resulting from the condensation of lauryllactam.

The notations PA X / Y, PA X / Y / Z, etc. relate to copolyamides in which X, Y, Z, etc. represent homopolyamide units as described above.

Advantageously, the polyamide blocks of the copolymer used in the invention comprise blocks of polyamide PA 6, PA 11, PA 12, PA 54, PA 59, PA 510, PA 512, PA 513, PA 514, PA 516, PA 518, PA 536, PA 64, PA 69, PA 610, PA 612, PA 613, PA 614, PA 616, PA 618, PA 636, PA 104, PA 109, PA 1010, PA 1012, PA 1013, PA 1014, PA 1016 , PA 1018, PA 1036, PA 10T, PA 124, PA 129, PA 1210,

PA 1212, PA 1213, PA 1214, PA 1216, PA 1218, PA 1236, PA 12T, or mixtures or copolymers thereof; and preferably comprise blocks of polyamide PA 6, PA 11, PA 12, PA 610, PA 1010, PA 1012, or mixtures or copolymers thereof.

Polyether blocks are made from alkylene oxide units.

The polyether blocks can in particular be blocks resulting from PEG (polyethylene glycol), ie consisting of ethylene oxide units, and / or blocks resulting from PPG (propylene glycol), ie consisting of oxide units of propylene, and / or blocks derived from P03G (polytrimethylene glycol), i.e. made up of polytrimethylene glycol ether units, and / or blocks derived from PTMG, i.e. made up of tetramethylene glycol units also called polytetrahydrofuran. The PEBA copolymers can comprise several types of polyethers in their chain, the copolyethers possibly being block or random.

It is also possible to use blocks obtained by oxyethylation of bisphenols, such as, for example, bisphenol A. These latter products are described in particular in document EP 613919.

The polyether blocks can also consist of ethoxylated primary amines. By way of example of ethoxylated primary amines, mention may be made of the products of formula:

H - (OCH ₂ CH ₂ ) _m - N - (CH ₂ CH ₂ 0) _n - H

(CH ₂ ) _X

CH ₃ in which 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.

The polyether blocks can comprise polyoxyalkylene blocks containing NH ₂ chain ends, such blocks being obtainable by cyanoacetylation of aliphatic α, w-dihydroxylated polyoxyalkylene blocks called polyetherdiols. More particularly, the commercial Jeffamine or Elastamine products can be used (for example Jeffamine® D400, D2000, ED 2003, XTJ 542, commercial products from the Huntsman company, also described in the documents JP 2004346274, JP 2004352794 and EP 1482011).

The polyetherdiol blocks are either used as such and copolycondensed with polyamide blocks having carboxylic ends, or aminated to be transformed into polyether diamines and condensed with polyamide blocks having carboxylic ends.

A general two-step preparation method of PEBA copolymers having ester bonds between the PA blocks and the PE blocks is known and is described, for example, in document FR 2846332. A general method of preparing PEBA copolymers having amide bonds between PA blocks and PE blocks is known and described, for example, in document EP 1482011. The polyether blocks can also be mixed with polyamide precursors and a diacid chain limiter to prepare polymers containing polyamide blocks and polyether blocks having units distributed in a statistical manner (one-step process).

Of course, the designation PEBA in the present description of the invention relates both to PEBAX® marketed by Arkema, to Vestamid® marketed by Evonik®, to Grilamid® marketed by EMS, and to Pelestat® type PEBA marketed by Sanyo or any other PEBA from other suppliers.

If the block copolymers described above generally comprise at least one polyamide block and at least one polyether block, the present invention also covers all the copolymers comprising two, three, four (or even more) different blocks chosen from those described in the present invention. description, provided that these blocks include at least polyamide and polyether blocks.

For example, the copolymer according to the invention can comprise a segmented block copolymer comprising three different types of blocks (or “triblock”), which results from the condensation of several of the blocks described above. Said triblock is preferably chosen from copolyetheresteramides and copolyetheramideurethanes.

Particularly preferred PEBA copolymers in the context of the invention are copolymers comprising blocks: PA 11 and derived from PEG; PA 11 and from PTMG; PA 12 and derived from PEG; PA 12 and derived from PTMG; PA 1010 and derived from PEG; PA 1010 and derived from PTMG; PA 610 and from PTMG; PA 610 and derived from PEG; PA 6 and derived from PEG; PA 6 and from PTMG.

The number-average molar mass of the polyamide blocks in the PEBA copolymer is preferably from 100 to 20,000 g / mol, more preferably from 200 to 10,000 g / mol, even more preferably from 200 to 2,000 g / mol. In embodiments, the number-average molar mass of the polyamide blocks in the PEBA copolymer is from 100 to 200 g / mol, or from 200 to 500 g / mol, or from 500 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 from 7000 to 8000 g / mol, or from 8000 to 9000 g / mol, or from 9000 to 10,000 g / mol, or 10,000 to 11,000 g / mol, or 11,000 to 12,000 g / mol, or 12,000 to 13,000 g / mol, or 13,000 to 14,000 g / mol, or 14,000 to 15,000 g / mol, or from 15000 to 16000 g / mol, or from 16000 to 17000 g / mol, or from 17000 to 18000 g / mol, or from 18000 to 19000 g / mol, or from 19000 to 20,000 g / mol.

The number-average molar mass of the polyether blocks is preferably from 100 to 6000 g / mol, more preferably from 200 to 3000 g / mol, even more preferably from 800 to 2500 g / mol. In embodiments, the number-average molar mass of the polyether blocks is 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 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 4000 to 4500 g / mol, or 4500 to 5000 g / mol, or 5000 to 5500 g / mol, or 5500 to 6000 g / mol.

The number-average molar mass is fixed by the chain limiter content. It can be calculated according to the relation:

Mn = nmonomer X MW repeat pattern / chain niimiter + MW chain limiter

In this formula, n _monomer represents the number of moles of monomer, ni _{chain imitor} represents the number of moles of excess limiter (for example diacid), MW repeat pattern represents the molar mass of the repeat pattern, and MWi _{chain imitor} represents the molar mass of the excess limiter (eg diacid).

The number-average molar mass of the polyamide blocks and of the polyether blocks can be measured before the copolymerization of the blocks by gel permeable chromatography (GPC).

The mass ratio of the polyamide blocks relative to the polyether blocks of the PEBA copolymer can in particular be from 0.1 to 20. This mass ratio can be calculated by dividing the number-average molar mass of the polyamide blocks by the number-average molar mass of the blocks. polyethers.

Thus, the mass ratio of the polyamide blocks relative to the polyether blocks of the PEBA copolymer can 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 from 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. Ranges from 2 to 19, and more specifically from 4 to 10, are particularly preferred.

Polyester block / polyether block copolymer (COPE)

According to one embodiment, the TP sc polymer is a COPE, also called a copolyetherester.

The COPEs according to the invention therefore include any thermoplastic elastomeric polymer comprising at least one polyether (PE) block, and at least one PES polyester block (homopolymer or copolyester).

COPEs comprise flexible PE blocks derived from polyetherdiols and rigid polyester blocks which result from the reaction of at least one dicarboxylic acid with at least one chain-extending short diol unit. The PES blocks and the PE blocks are linked by ester bonds resulting from the reaction of the acid functions of dicarboxylic acid with the OH functions of the polyetherdiol. The short chain-extending diol can be chosen from the group consisting of neopentylglycol, and aliphatic glycols of formula HO (CH) _n OH in which n is an integer of 2 to 10. The sequence of polyethers and diacids forms the flexible blocks whereas the linking of the glycol or of the butanediol 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 can be replaced by at least one other aromatic dicarboxylic acid having 8 to 14 carbon atoms, and / or up to 20 mole% can be replaced by an aliphatic acid dicarboxylic having 2 to 14 carbon atoms. By way of example of aromatic dicarboxylic acids, mention may be made of terephthalic, isophthalic, bibenzoic acid, naphthalene dicarboxylic, 4,4'-diphenylenedicarboxylic acid, bis (p-carboxyphenyl) methane acid, ethylene bis p-benzoic acid, 1 -4 tetramethylene bis (p-oxybenzoic) acid, ethylene bis (p-oxybenzoic) acid, 1, 3-trimethylene bis (p-oxybenzoic) acid. By way of example of glycols, mention may be made of ethylene glycol, 1, 3-trimethylene glycol, 1, 4-tetramethylene glycol, 1, 6-hexamethylene glycol, 1, 3 propylene glycol, 1, 8 octamethylene glycol, 1, 10-decamethylene glycol.

COPEs are copolymers having PE units derived from polyetherdiols as defined above, for example polyethylene glycol (PEG), polypropylene glycol (PPG), polytrimethylene glycol (P03G) or polytetramethylene glycol (PTMG), and units PES resulting from the reaction of a dicarboxylic acid such as terephthalic acid with a glycol, ethane diol or 1, 4-butanediol. Such copolyetheresters are described in patents EP402883 and EP405227.

Thermoplastic polyurethane (TPU)

According to one embodiment, the semi-crystalline thermoplastic polymer is a TPU, i.e. a copolymer with polyurethane (PU) blocks and polyether (PE) blocks, also called polyetherurethane.

TPUs result from the condensation of flexible PE blocks which are polyetherdiols and rigid PU blocks. The PU blocks and the PE blocks are linked by bonds resulting from the reaction of the isocyanate functions of the polyurethane with the —OH functions of the polyetherdiol.

By PU within the meaning of the invention is meant the products resulting 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 chain-extending diol can be chosen from the glycols mentioned above in the description of the copolyetheresters. The PUs entering into the composition of the copolymers according to the invention can comprise all types of polyols, and in particular those of renewable origin, such as polyols derived from starch (erythritol, sorbitol, maltitol, mannitol), the polyols derived from sugars such as sucrose (isomalt, xylitol), polyols from corn, soybeans, cotton, rapeseed, sunflower or peanuts (glycerol, propylene glycol, ethylene glycol, reaction co-product of biodiesel production ). As others examples of polyols which can enter into the composition of these polyurethanes, one can also quote the polyethylene glycol (PEG), the poly (1, 2-propylene glycol) (PPG), the poly (1, 3-propylene glycol) (P03G) , polytetramethylene glycol (PTMG).

According to one embodiment, the semi-crystalline elastomeric thermoplastic polymer can also be chosen from styrene block copolymers (TPS), thermoplastic polyolefin elastomers (TPO), thermoplastic vulcanizates (TPV). Examples of commercial materials originating from commercial thermoplastic elastomeric polymers are for example the products 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 one embodiment, the semi-crystalline thermoplastic polymer is a polymer chosen from homopolymers and copolymers of polyoxymethylene (POM), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyterephthalate of butylene (PBT), polyphthalamides (PPA), and poly (p-phenyleneterephthalamide).

Wax

The wax of the invention is generally a solid compound at room temperature. The wax can be malleable at 20 ° C.

The wax may have a coarse to fine crystal structure, translucent to opaque in appearance but not glassy. Wax can begin to melt above 40 ° C without breaking down. The wax may exhibit a melt viscosity (less than 10,000 mPa.s) at 10 ° C above its dropping point.

The wax can be a hydrophobic compound.

The wax used in the invention may in particular be chosen from synthetic waxes, such as polyolefin waxes, waxes of mineral (eg Montan's wax), petroleum or vegetable origin (eg carnauba wax or wax of candelilla) or animals as well as their mixtures.

The wax as mentioned above generally consists of hydrocarbon compounds comprising from 10 to 100 carbon atoms, preferably from 15 to 60 carbon atoms. According to a particularly interesting embodiment, the wax is a wax of the aforementioned functionalized type which can comprise at least one polar group chosen from an ester, an ether, an acid, an acid anhydride, a carboxylate, an amide, an amine or an alcohol, preferably an ester, an acid, an acid anhydride, or an amide.

The acidic group is typically a carboxylic acid.

A functionalized wax can be obtained by functionalizing an existing wax, in particular by oxidation reaction or grafting reaction. Alternatively, the functionalized wax can be obtained by introducing monomers bearing functional groups during the polymerization reaction.

Without wishing to be bound by a particular theory, it seems that these polar groups are capable of interacting with the TP sc polymer by creating a weak bond on the surfaces of the TP sc polymer powder, for example, of the hydrogen type, Van der Waals which makes it possible to improve the cohesion of the powder and to increase the hardness of the powder bed, in particular at the construction temperature.

Preferably, the wax used in the context of the invention has an acid number ranging from 2 to 100, preferably 3 to 90 mg KOH / g, for example ranging from 2 to 10, or from 10 to 20, or from 20 to 50, or from 50 to 90 mg KOH / g. When a TP sc polymer of the polyamide or PEBA type is used in the context of the present invention, it has been observed that the higher the acid number of the wax, the stronger the cohesion of the powder bed for them. waxes having similar dropping points.

In the context of the invention, the acid number was measured according to DIN EN ISO 2114 - November 2000, using a 50:50 v / v xylene / ethanol mixture as the titration solvent.

The 1g wax sample was weighed in a 250ml Erlenmeyer flask and dissolved in 100ml of the hot xylene / ethanol mixture (about 90 ° C) on a magnetic stirrer.

The sample was then placed on the magnetic stirrer of the titrimeter, the electrode was well immersed and the mixture was titrated with an ethanolic solution of KOH at a concentration of 0.1 M.

According to one embodiment, the wax can be chosen from polyethylene and polypropylene waxes, polytetrafluoroethylene waxes, ketone waxes, acid waxes, partially esterified acid waxes, waxes. acid anhydride, ester waxes, aldehyde waxes, amide waxes, their derivatives and mixtures thereof, preferably polyethylene and polypropylene waxes, acid waxes, waxes of partially esterified acids, acid anhydride waxes, ester waxes, amide waxes, their derivatives and / or mixtures thereof.

Waxes can typically be dry or melt mixed.

The polyolefin waxes can be homopolymers of ethylene and / or propylene and / or 1 -butene. Polyolefin waxes can be copolymers of two or more olefins (eg, polymers of mixtures of ethylene, propylene and / or 1 -butene). They can also be copolymers of ethylene and of propylene. According to one embodiment, the polyolefins can be linear or branched polyolefins having from 20 to 200 carbon atoms, and preferably from 40 to 100 carbon atoms. They can also be substituted by aliphatic and / or aromatic groups. Examples of such polyolefins include 1-hexene, 1-octene or 1-octadecene, styrene. For example, a polyolefin wax used in the context of this invention is wax "Crayvallac ILΆ / 7495 ^®" marketed by Arkema.

A polytetrafluoroethylene wax which can be used in the context of the invention is the "Ceridust 9202F®" wax sold by Clariant or the "Crayvallac WF-1000®" wax by Arkema.

An acid wax which can be used in the context of the invention is the "Licowax S®" wax sold by Clariant.

An ester wax which can be used in the context of the invention is polyhydroxyalkanoate wax, for example, the “Ceraflour 1000®” wax sold from Byk, and the “Licowax OP®” wax sold from Clariant.

According to one embodiment, the wax can be a wax derived from crude oil, such as paraffins. Paraffin waxes primarily contain straight chain hydrocarbons and may also contain branched hydrocarbons, such as isoparaffins and other branched materials, and cycloalkanes, such as cycloparaffins and other cyclic materials. According to one embodiment, the polyolefin waxes can be functionalized with acid anhydrides such as maleic anhydride. For example, such a wax is the wax “Ceridust 802 (” marketed by the company CLARIANT.

Amide waxes can be prepared by reacting a long chain carboxylic acid (typically a fatty acid) with an amine, diamine, or ammonia.

According to a particular embodiment, the amide wax comprises a diamide obtained from a diamine chosen from a C2 to C24 aliphatic diamine, a C6 to C18 cycloaliphatic diamine, a C6 to C24 aromatic diamine, or their mixtures.

An aliphatic diamine can be linear or branched, preferably linear. Examples of suitable linear aliphatic amines are 1, 2-ethylenediamine, 1, 3-propylenediamine, 1, 4-tetramethylenediamine, 1, 5-pentamethylenediamine, 1, 6-hexamethylenediamine, 1, 8-octamethylenediamine, 1, 12-dodecamethylenediamine and their mixtures; preferably 1, 2-ethylenediamine, 1, 5-pentamethylenediamine and 1, 6-hexamethylenediamine. Examples of suitable branched aliphatic amines are 1, 2-propylenediamine, 2,2-dimethyl-1, 3-propanediamine, 2-butyl-2-ethyl-1, 5-pentanediamine and mixtures thereof.

A cycloaliphatic diamine is a non-aromatic diamine comprising a ring, in particular a ring having 6 carbon atoms. A C6 to C18 cycloaliphatic diamine is a cycloaliphatic diamine comprising 6 to 18 carbon atoms. Examples of suitable cycloaliphatic diamines are 1, 2-, 1, 3- or 1, 4-diaminocyclohexane, 2-methylcyclohexane-1, 3-diamine, 4-methylcyclohexane-1, 3-diamine, isophoronediamine, 1, 2-, 1, 3- or 1, 4- bis (aminomethyl) cyclohexane, diaminodecahydronaphthalene, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, bis (aminomethyl) norbornane and mixtures thereof; preferably 1, 3- or 1, 4- bis (aminomethyl) cyclohexane, 1, 2-, 1, 3- or 1, 4-bis (aminomethyl) cyclohexane, isophorone diamine and 4,4'-diaminodicyclohexylmethane.

An aromatic diamine is a diamine comprising an aromatic ring. A C6 to C24 aromatic diamine is an aromatic diamine comprising 6 to 24 carbon atoms. Examples of suitable aromatic diamines are meta- and para-phenylenediamine, meta- and para-xylylenediamine, meta- and para-toluylenediamine, 3,4'-diaminodiphenylether, 4,4'-diaminodiphenylether, 4,4'- diaminodiphenylmethane and mixtures thereof; preferably meta- and para- xylylenediamine.

Preferably, the amide wax comprises a diamide obtained with at least one diamine chosen from a C2 to C24 aliphatic diamine, in particular a linear C2 to C18 aliphatic diamine, more particularly a linear C2 to C12 aliphatic diamine, more particularly still 1, 2-ethylenediamine, 1, 5-pentamethylenediamine or 1, 6-hexamethylenediamine. According to a particular embodiment, the amide wax comprises a diamide obtained with at least one C2 to C36 carboxylic acid. The diamide can be obtained with a mixture of C2 to C36 carboxylic acids.

The carboxylic acid can be linear or branched, preferably linear. The carboxylic acid can be saturated or unsaturated, preferably saturated. The carboxylic acid can be unsubstituted or substituted, especially hydroxylated. A hydroxylated carboxylic acid is a carboxylic acid substituted with one or two hydroxyl groups, preferably with one hydroxyl group.

According to a particular embodiment, the carboxylic acid can be a hydroxylated carboxylic acid optionally mixed with an unsubstituted carboxylic acid.

Suitable examples of hydroxy carboxylic acids are 12-hydroxy stearic acid (12-HSA), 9-hydroxy stearic acid (9-HSA), 10-hydroxystearic acid (10-HSA), 14-hydroxy eicosanoic acid (14 -HEA), 2,2- bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butyric acid, hydroxy-acetic acid (or glycolic acid), 2-hydroxy propionic acid (lactic acid), 2-hydroxy acid -3- (3-pyridyl) propionic, 3-hydroxy butyric acid, 2-hydroxy butyric acid, 2-methyl-2-hydroxy butyric acid, 2-ethyl-2-hydroxy butyric acid, hydroxy pentanoic acid, hydroxy hexanoic acid, hydroxy heptanoic acid, hydroxy octanoic acid, hydroxy nonanoic acid, hydroxy decanoic acid and mixtures thereof; preferably 12-hydroxy stearic acid or a binary or ternary mixture of 12-hydroxy stearic acid with the other aforementioned hydroxyl acids.

Suitable examples of unsubstituted carboxylic acids are acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, eicosanoic acid, palmitoleic acid, oleic acid, 11-eicosenoic acid, erucic acid, nervonic acid, linoleic acid, α-linolenic acid, g-linolenic acid, dihomo- g-linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and mixtures thereof; preferably decanoic acid.

Preferably, the amide wax comprises a diamide obtained with at least one carboxylic acid chosen from a C2 to C22 carboxylic acid, in particular a C2 to C22 hydroxylated carboxylic acid and optionally an unsubstituted C2 to C22 carboxylic acid. , more particularly a C12 to C20 hydroxylated carboxylic acid and optionally an unsubstituted C2 to C14 carboxylic acid. According to a preferred embodiment, the amide wax comprises a diamide obtained by reaction between 1, 2-ethylenediamine or 1, 6-hexamethylene diamine and 12-hydroxystearic acid or optionally decanoic acid.

Amide waxes can be compounds prepared by reacting ammonia or ethylenediamine with saturated and / or unsaturated fatty acids such as stearic acid, tallow fatty acid, palmitic acid, erucic acid. Amide waxes also can include amide compounds such as N, N'-ethylenedistearamide. For example, such a wax is wax "Crayvallac WN1265 ^®" marketed by Arkema.

According to one embodiment, the polyolefin waxes can be mixed with amide waxes. For example, such waxes are: wax "Crayvallac WN1 135" sold by the company Arkema, wax "Ceridust ^® 9615A" - a mixture of polyethylene wax and amide wax, available from Clariant.

According to one embodiment, the wax can be chosen from fatty acid derivatives, such as partially or fully esterified fatty acids. Preferably, they are fatty acids comprising at least 10 carbon atoms, preferably 16 to 60 carbon atoms, and more preferably 24 to 36 carbon atoms. Preferably, they are saturated alkanemonocarboxylic acids, preferably linear, such as montanic acid. As an example of this type of wax, mention may be made of the “Ceridust 5551®” wax sold by the company CLARIANT.

For the purposes of the present invention, the wax does not include fatty acid salts comprising at least 10 carbon atoms, preferably from 16 to 60 carbon atoms, and more preferably from 24 to 36 carbon atoms (also called of "Metallic soaps"). Typically, they are the salts of saturated alkanemonocarboxylic acids, preferably linear, such as montanic acid and stearic acid. Typically, these are the calcium and / or sodium and / or magnesium salts. For example, such waxes are wax "Licomont NAV101 ^®" marketed by Clariant, calcium stearate or magnesium.

It has been observed that the use of such a salt as a wax, in combination with a powder of semi-crystalline thermoplastic polymer, in particular an elastomer, for example with a powder of PEBA copolymer, does not make it possible to increase the powder. working window nor to ensure good cohesion of the bed.

However, it is possible to use such a salt as additives in TP sc polymer powders used in sintering, for example to improve flow as described in US 2006/0189784 or to reduce thermal stress during sintering. as described in US 2008/0300353.

According to one embodiment, the wax in the composition of the invention is nonionic.

The wax can be a mixture of the ester wax functionalized with an alcohol. Mention may be made of the “Licolub WE 40®” wax sold by the company CLARIANT.

The vegetable waxes can comprise, for example, derivatives of castor oil, functionalized or not. As wax derived from castor oil include wax "Crayvallac PC ^®" marketed by Arkema, and wax "Jagrowax 100 *" sold by Jayant Agro-Organics.

According to the invention, the wax has a dropping point higher than the crystallization temperature (Te) of the TP sc polymer.

By “dropping point” is meant the temperature at which the wax changes from a semi-solid state to a liquid state under specific test conditions. The dropping point is measured according to standard ASTM D 3954 - 1994 (2004). Preferably, the wax according to the invention can have a dropping point greater than the Tm of the TP sc polymer of at most 30 ° C, and preferably at most 20 ° C. For example this difference can be from 1 to 5 ° C; or from 5 to 10 ° C; or from 10 to 15 ° C; or from 15 to 20 ° C; or from 20 to 25 ° C; or 25 to 30 ° C.

In particular, the wax can have a dropping point of 60 to 180 ° C, and preferably 80 to 175 ° C. For example this dropping point can be 60 to 65 ° C; or from 65 to 70 ° C; or from 70 to 75 ° C; or from 75 to 80 ° C; or 8 (& 85 ° C; or 85 to 90 ° C; or 90 to 95 ° C; or 95 to 100 ° C; or 100 to 105 ° Q or 105 to 110 ° C; or 110 to 115 ° C; or from 115 to 120 ° C; or from 120 to 125 ° Q or from 125 to 130 ° C; or from

130-135 ° C; or from 135 to 140 ° C; or from 140 to 145 ° Q or from 145 to 150 ° C; or from

150 to 155 ° C; or from 155 to 160 ° C; or from 160 to 165 ° Q or from 165 to 170 ° C; or from

170-175 ° C; or 175 to 180 ° C.

The present invention proposes to use a particular wax, the dropping point of which is greater than the Te of the polymer TP sc. Thus, the wax is in the molten state or at least partially molten at the temperature of the powder bed, and can increase the cohesion of the TP sc polymer powders by a kind of sticking, which results in increasing the rigidity of the powder bed and prevents the part from sinking into the bed.

Typically, the wax's dropping point is greater than the Te of the TP sc polymer by at least 5 ° C, preferably by at least 10 ° C, by [Deference by at least 15 ° C, and further by preferably at least 20 ° C. For example, this temperature difference can be 5 to 10 ° C; or from 10 to 15 ° C; or from 15 to 20 ° C; or from 20 to 25 ° C; or from 25 to 30 ° C; or from 30 to 35 ° C; or 35-40 ° C; or from 40 to 45 ° C; or 45 to 50 ° C.

Powder composition

According to the present invention, the composition of the powder is semi-crystalline, that is, the transformation into powder of the TP sc polymer and the preparation of the powder composition does not affect the semi-crystalline character of the TP sc polymer as defined. above.

The composition according to the invention may comprise the TP sc polymer (s) in a proportion by weight preferably greater than or equal to 80%, or to 81%, or to 82%, or to 83%, or to 84%. , or 85%, or 86%, or 87%, or 88%, or 89%, or 90%, or 91%, or 92%, or 93%, or 94% , or 95%, or 96%, or 97%, or 98%, or 99%, or 99.1%, or 99.2%, or 99.3%, or 99.4%, or 99.5%, or 99.6%, or 99.7%, or 99.8%, or 99.9%, or 99.91%, or 99.92%, or 99.93%, or 99 , 94%, or 99.95%, or 99.96%, or 99.97%, or 99.98%, or 99.99%.

Typically, the TP sc polymer particles can have a Dv50 size of 40 to 150 µm, and preferably 50 to 100 µm. For example, the size Dv50 of the TP sc polymer particles can be 40-45 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 from 145 to 150 pm.

Typically, the composition comprises a wax at a content of 0.1 to 20% by weight of the total composition, preferably 0.5 to 10%, and more preferably 0.5 to 5% by weight. Thus, this content can 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 from 0.5 to 1%; or from 1 to 2%; or from 2 to 4%; or from 4 to 6%; or from 6 to 8%; or from 8 to 10%; or from 10 to 12%; or from 12 to 14%; or from 14 to 16%; or from 16 to 18%; or from 18 to 20%.

The wax can be present in the composition in the form of wax particles. Typically, the wax particles have an average size (Dv50) of 1 to 30 µm, preferably 1 to 20 µm, and more preferably 5 to 15 µm.

Preferably, a wax is chosen whose average size (Dv 50) is smaller than that of the TP sc polymer in the composition.

The wax can also have a Dv90 size of less than 50 µm, and preferably less than 20 µm. For example, the size Dv90 of the wax particles can be 5 to 20 µm; or from 5 to 15 pm.

In the context of this request:

- the Dv50 corresponds to the particle size threshold for which 50% of the particles (by volume) have a size below the threshold, and 50% of the particles (by volume) have a size above the threshold;

- the Dv90 corresponds to the particle size threshold for which 90% of the particles (by volume) have a size below the threshold, and 10% of the particles (by volume) have a size above the threshold. The Dv50 and the Dv90 are measured according to the ISO 9276 standard - parts 1 to 6: “Representation of data obtained by particle size analysis”. It is possible to use, for example, a laser particle size analyzer (Sympatec Helos) and software (Fraunhofer) to obtain the volumetric distribution of a powder and to deduce the Dv50 and the Dv90 therefrom.

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

Flow agent

According to one embodiment, the composition according to the invention comprises one or more flow agents.

By "flow agent" is meant an agent which improves the flowability as well as the leveling of the powder of semi-crystalline thermoplastic polymers during the sintering process.

It has been observed that the presence of a flow agent in a TP sc polymer composition can reduce the working window, making construction more difficult. In addition, the problem of bed cohesion is more often encountered when a flow agent is used.

The use of wax in the composition of the invention proves to be particularly advantageous in these cases: it makes it possible to widen the working window and also to avoid the problem of the cohesion of the bed, thus making it possible to carry out a construction. more easily.

The flow agent can be chosen from those commonly used in the field of sintering powders of TP sc polymers. It is for example chosen from: silicas, in particular precipitated silicas, hydrated silicas, vitreous silicas, fumed silicas, pyrogenic silicas, vitreous oxides, in particular vitreous phosphates, vitreous borates, alumina, such as amorphous alumina, Ti02, calcium silicates, magnesium silicates, such as talc, mica, kaolin, attapulgite, and mixtures thereof.

The flow agent is generally present in the composition at a content of less than or equal to 5% by mass of the total composition, preferably less than or equal to 3%. Typically this content can be 0.1 to 2.5%, for example 0.1 to 2%, preferably 0.5 to 2%, or 0.5 to 1.5%.

The flow agent is generally in powder form, preferably substantially spherical in shape.

The flow agent in the composition of the powder may be in the form of particles having an average size (Dv50) less than or equal to 20 μm, preferably less than or equal to 15 μm, preferably less than or equal to 10 μm, and more preferably less than or equal to 1 μm. For example, the Dv50 size of the flow agent particles can be 10nm to 100nm, 100nm to 1µm, 1µm to 20µm.

Other additives

The composition according to the invention can comprise any type of additive suitable for the powders of TP sc polymers used in sintering: in particular additives (in powder form or not) which contribute to improving the properties of the powder for its use in technology. agglomeration and / or additives making it possible to improve the properties, for example, the mechanical properties (for example modulus, elongation at break, impact resistance) or else the aesthetic properties (color) of the three-dimensional parts manufactured.

According to an interesting embodiment, the composition according to the invention can comprise mineral additives, for example, carbonate minerals, in particular calcium carbonate, magnesium carbonate, dolomite, calcite, barium sulphate, sulphate. calcium, dolomite, alumina hydrate, wollastonite, montmorillonite, zeolite, perlite, nanofillers (fillers of the order of nanometers) such as nanoclays or carbon nanotubes, black of carbon, glass fibers, carbon fibers, organic additives such as polymer powders having a melting point higher than the maximum temperature undergone by the composition during the layer-by-layer construction process, in particular those of modulus greater than 1000 MPa.

According to one embodiment, the composition is devoid of mineral additives and organic additives.

The additives of the aforementioned type can be present in the composition of the powder (including those present where appropriate in the TP sc polymer powders) at a mass content of less than or equal to 60%, preferably less than or equal to 30%, more preferably less than or equal to 1%. For example at a mass content of 0.05 to 60%; or from 1 to 30%; or from 1 to 20%; or from 1 to 10%. The composition of the invention can also comprise dyes, pigments for coloring, pigments for infrared absorption, anti-fire additives, anti-oxygen stabilizers, light stabilizers, anti-shock agents, anti-static agents, flame retardants, and mixtures thereof. These additives are preferably in the form of a powder with a Dv50 of less than 20 μm. These additives can be present in the composition at a content of 0.05 to 5%.

The additives can be mixed with the TP sc polymer before and / or after the grinding step described above.

Process for preparing the composition

The composition according to the invention comprises powders of semi-crystalline thermoplastic polymer and at least one wax.

The process for preparing the composition of the present invention comprises a step where the TP sc polymer is contacted with the wax, and optionally a flow agent.

The TP sc polymers which can be used in the context of the invention are for the most part commercially available, in particular in the form of granules, scales or coarse powder, which can be easily converted into powder by means of known methods.

Generally, TP sc polymer powder can be obtained by a grinding process.

Preferably, the TP sc polymer brought into contact with the wax is in powder form; alternatively, in the form of granules, scales or coarse powder, for example having a Dv50 size greater than 250 μm (In this case, a grinding and / or sieving step can be carried out.)

According to one embodiment, the contacting of the TP sc polymer with the wax is carried out by mixing dry, that is to say in the absence of solvent. According to one embodiment, the placing of the TP sc polymer into contact with the wax is carried out according to the following steps:

- dissolving the wax in an appropriate solvent to form a wax solution to form a wax solution;

- by mixing said wax solution with the TP sc polymer to form a dispersion; and

- By removing the solvent from said dispersion, for example by evaporation, to obtain the TP sc polymer coated with wax.

The suitable solvent may be a solvent known to those skilled in the art to be able to dissolve a wax, for example, acetone, ethanol and / or a solvent comprising water and a surfactant.

The preparation process may include a grinding step in order to obtain a TP sc polymer powder of the desired particle size.

The grinding step can be carried out before and / or after contacting the TP sc polymer with the wax.

Preferably, the grinding is cryogenic grinding known to those skilled in the art Thus, firstly, the TP sc polymer (or the mixture of TP sc polymer and wax) is cooled to a temperature below the transition temperature. glassy of the polymer TP sc. This temperature can be 10 to 50 ° C lower than the glass transition temperature of the TP sc polymer. Thus, the mixture can be cooled to a temperature less than or equal to -10 ° C, preferably less than or equal to -50 ° C, and more preferably less than or equal to -80 ° C.

The cooling of the TP sc polymer (or of the mixture of TP sc polymer and wax) can be carried out for example with liquid nitrogen, or with liquid carbon dioxide or with dry ice, or with liquid helium .

The grinding step can be carried out in a counter-rotating pin mill (pin mill), a hammer mill (hammer mill) or in a whirl mill.

The method for preparing the composition according to the invention can then comprise a sieving step. The sieving can be carried out on a sieve. Alternatively, after grinding, the preparation process can include a selection step to obtain the desired particle size profile. Typically, the powders can be dispersed by a selection wheel and carried by classifying air. Dust entrained in the air is fed through a support wheel and discharged through a first outlet. The coarse product is rejected by a classification wheel and transported to a second outlet. The selector can include several successive wheels working in parallel.

When the additives mentioned above (including the flow agent) are present in the composition, the TP sc polymer (or the mixture of TP sc polymer and wax) is contacted with the additives in powder form. , (ie in the form of a simple mixture) before or after the grinding and / or sieving step.

According to a particular embodiment, certain specific additives, such as mineral additives, can be incorporated into the TP sc polymer powders by compounding, in particular at the stage of the manufacture of the TP sc polymer granules intended to be ground.

Moreover, for certain specific TP sc polymers, for example, polyamides, a dissolution-precipitation process can be envisaged for the preparation of powder. In this particular case, the wax can be introduced during the dissolution-precipitation process.

Method of sintering the composition

The composition, as described above, is used for a method of constructing layer-by-layer 3D articles by sintering caused by electromagnetic radiation, for example infrared, ultraviolet, or preferably laser radiation.

According to the process, a thin layer of powder is deposited on a horizontal plate maintained in an enclosure heated to a temperature called the construction temperature. The term "build temperature" (also called "bed temperature") refers to the temperature to which the powder bed, of a constituent layer of a three-dimensional object under construction, is heated during the layer-by-layer sintering process. powder layer. This temperature may be lower than the melting temperature of the TP sc polymer of less than 50 ° C, from preferably less than 40 ° C, and more preferably about 20 ° C. The electromagnetic radiation then provides the energy necessary 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 an amount corresponding to the thickness of a powder layer, and a new layer is deposited. The electromagnetic radiation provides the energy necessary to sinter the powder particles according to a geometry corresponding to this new slice of the object and so on. The procedure is repeated until the object has been manufactured.

Preferably, the layer of powder deposited on a horizontal plate (before sintering) may have a thickness of 20 to 200 μm, and preferably of 50 to 150 μm. The layer of agglomerated material after sintering may have a thickness of 10 to 150 µm, and preferably 30 to 100 µm.

Preferably, the composition of the invention is used in a selective laser sintering process (SLS). The composition can also be used in a sintering process of the MJF (Multi Jet Fusion) and HSS (High Speed Sintering) type.

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

The powder composition, as described above, can be recycled and reused in several successive constructions. It can, for example, be used as it is or as a mixture with other powders, whether or not they are recycled.

The following examples illustrate the invention without limiting it.

EXAMPLES

Example 1

Different powders of PEBA copolymers are optionally mixed with a flow agent (silica) at a rate of 1% (for polymer A), 0% (for polymer B) by weight and optionally with a wax at a rate of 1. % in weight. The table below includes the different PEBAs used in the context of this example.

Table 1: Composition of the polymers used

Thus, polymers A and B were mixed with flow agent and with a wax so as to form compositions 1 to 11. These compositions were used for the manufacture of three-dimensional articles.

Table 2: Composition of polymer powder and wax studied

It was found that the presence of wax having a dropping point greater than the Te of the polymer allows the composition to pass through a sintering machine so as to obtain 3D articles (compositions 2 to 6 and 8). The absence of wax does not allow the composition to pass through the sintering machine (compositions 1 and 7). In the cases of composition 9, it was found that when the dropping point of the wax is lower than the Te of the polymer, the manufacture of 3D articles was not possible. In the case of the wax-free compositions 10 and 11, it was found that the use of salts does not make it possible to increase the working window or to ensure the cohesion of the bed, the manufacture of 3D articles was not possible. Not possible. Example 2

A PA12 powder is mixed with silica at a rate of 0.15%. This powder has a Tm equal to 180 ° C and a Te equal to 147 ° C measured according to the ISO 11357 standard.

This powder is dry mixed with a wax so as to form compositions 1 and 2. These compositions were used for the manufacture of three-dimensional articles.

The wax used is a polyhydroxyalkanoate (PHA), a product marketed under the trademark Ceraflourl 000® from BYK. The working window is determined for compositions 1 and 4.

For composition 1, sinking of the parts is observed below 160 ° C.

Composition 2 allows construction of three-dimensional objects over a wider temperature range, so this formulation has a larger working window.

On the other hand, it has been observed that the addition of wax accelerates the crystallization of the polymer, i.e. the crystallization temperature becomes higher. This effect is visible by melting the polymer at 220 ° C. then by observing the isothermal crystallization in DSC at 160 ° C. It is seen that the rate of crystallization of composition 2 is greater than that of composition 1 without wax. Surprisingly, even if the crystallization temperature is higher, the presence of wax nevertheless allows the printing to be carried out below 160 ° C.

Claims

Claims

1. Composition for the construction of a three-dimensional (3D) article layer by layer, by sintering of the composition, caused by electromagnetic radiation, the composition comprising:

a powder of semi-crystalline thermoplastic polymer;

a wax, the wax having a dropping point higher than the crystallization temperature (Te) of the semi-crystalline thermoplastic polymer;

- and optionally a flow agent.

2. Composition according to claim 1, in which the wax is chosen from polyolefin waxes, waxes of plant or animal origin, and mixtures thereof.

3. Composition according to claim 2, in which the wax is chosen from polyethylene and polypropylene waxes, polytetrafluoroethylene waxes, ketone waxes, acid waxes, partially esterified acid waxes, waxes of acid anhydride, ester waxes, aldehyde waxes, amide waxes, their derivatives and mixtures thereof.

4. Composition according to one of claims 1 to 3, in which the semi-crystalline thermoplastic polymer is chosen from a polyamide, a homopolymer or copolymer of vinylidene fluoride (PVDF), a copolymer with polyamide blocks and polyether blocks (PEBA ), a thermoplastic polyurethane (TPU), a polyester block and polyether block copolymer (COPE) and mixtures thereof.

5. Composition according to claim 4, in which the semi-crystalline thermoplastic polymer is an elastomer selected from a PEBA, a TPU, a COPE and their mixtures.

6. Composition according to one of claims 4 to 5, in which the polyamide is chosen from polyamide (PA) 11, PA 12, or PA 6.

7. Composition according to one of claims 4 to 5, in which the polyamide blocks of PEBA are blocks of PA 6, PA 11, PA 12, PA 610, PA 1010 or PA 1012; and / or in which the polyether blocks of PEBA are blocks obtained from PEG (polyethylene glycol), PPG (propylene glycol), P03G (polytrimethylene glycol) or PTMG (polytetrahydrofuran).

8. Composition according to one of the preceding claims, in which the wax is present in a content of 0.1 to 20%, preferably from 0.5 to 10%, and more preferably from 0.5 to 5% in mass of the total composition.

9. Composition according to one of the preceding claims, in which the dropping point of the wax is greater than the crystallization temperature of the semi-crystalline thermoplastic polymer by at least 5 ° C, preferably at least 10 ° C, preferably at least 15 ° C, and more preferably at least 20 ° C.

10. Composition according to one of the preceding claims, in which the dropping point of the wax is greater than the melting point of the semi-crystalline thermoplastic polymer by at most 30 ° C, and preferably at most 20 ° C. .

11. The composition of claim 1, wherein the flow agent is present at a content of less than or equal to 5% by mass of the total composition.

12. Composition according to claim 11, in which the flow agent is chosen from: silicas, in particular precipitated silicas, hydrated silicas, vitreous silicas, fumed silicas, pyrogenic silicas, vitreous oxides, in particular vitreous oxides. glassy phosphates, glassy borates, alumina, such as amorphous alumina, TiO2, calcium silicates, magnesium silicates, such as talc, mica, kaolin, attapulgite, and mixtures thereof.

13. Use of the composition according to one of claims 1 to 12, for the construction of a layer-by-layer 3D article, by sintering the composition caused by electromagnetic radiation, preferably by laser radiation.

14. Use according to claim 13, in which the composition is reused in several successive constructions.

15. 3D article made from the composition according to one of claims 1 to 12, preferably by layer-by-layer construction by sintering caused by electromagnetic radiation, preferably by laser radiation.

16. Use of a wax to increase the cohesion of the bed of semicrystalline thermoplastic polymer powder, in a sintering process by electromagnetic radiation, preferably by laser radiation.

17. Use of a wax in a powder composition based on a semi-crystalline thermoplastic polymer to improve the recyclability of powders in a construction of 3D articles by sintering.

18. Use according to claim 16 or 17, wherein the wax and / or the semi-crystalline thermoplastic polymer are as defined in one of claims 1 to 12.