EP3969501A1

EP3969501A1 - Copolymer powder with polyamide blocks and polyether blocks

Info

Publication number: EP3969501A1
Application number: EP20737239.2A
Authority: EP
Inventors: Alexis MORFIN; Benoît BRULE; Apolline PALAIS; Nadine Decraemer
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2019-05-16
Filing date: 2020-05-15
Publication date: 2022-03-23
Also published as: FR3096053B1; US20220213274A1; CN113950510A; JP2022532376A; JP7564827B2; KR20220010607A; CN113950510B; FR3096053A1; WO2020229782A1

Abstract

A powder of a copolymer with polyamide blocks and polyether blocks. The invention concerns a composition comprising a powder of a copolymer with polyamide blocks and polyether blocks, the copolymer being in particle form with a pulverulent filler content of 0 to 10 % by mass and the copolymer having a ratio by mass of the polyamide blocks to the polyether blocks of less than or equal to 0.7, the polyamide blocks having a number-average molar mass of less than or equal to 1000 g/mol; and the composition comprising a flow aid at a content of greater than or equal to 0.3 % by mass. The invention also concerns the process for producing this composition, the use of the composition for constructing three-dimensional articles, and the three-dimensional articles manufactured from said composition.

Description

Copolymer powder containing polyamide blocks and polyether blocks Field of the invention

The present invention relates to a powder composition for a copolymer containing polyamide blocks and polyether blocks, as well as its method of preparation. The invention also relates to the use of this powder and to articles made from it.

Technical background

Copolymers with polyamide blocks and polyether blocks or “Polyether-Block-Amide” (PEBA) are thermoplastic elastomers without plasticizers which belong to the family of technical polymers. They can be easily processed by injection molding and extrusion of profiles or films. They can also be used in the form of filaments, threads and fibers for fabrics and nonwovens. They are used in the sports field in particular as parts of the soles of sports shoes or golf balls, in the medical field, in particular in catheters, angioplasty balloons, peristaltic belts, or in the automobile sector, in particular as synthetic leather, skins, dashboard, airbag element.

PEBAs, marketed under the name Pebax® by Arkema, make it possible to combine, in the same polymer, unequaled mechanical properties with very good resistance to thermal or UV aging, as well as low density. They thus allow the development of light and flexible parts. In particular, at equivalent hardness, they dissipate less energy than other materials, which gives them very good resistance to dynamic stresses in bending or traction, and they exhibit exceptional springback properties.

These polymers can also be used in the field of construction of three-dimensional articles by sintering. 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 rapidly to lead to the formation of a solid mass. This process can easily and quickly produce three-dimensional articles by repeated irradiation of a succession of freshly applied powder layers. This technology is generally used to produce prototypes, models of parts ("rapid prototyping ") or to produce finished parts in small series (" rapid manufacturing "), for example in the automotive, nautical, aeronautics, aerospace, medical fields (prostheses, hearing systems , cellular fabrics), textiles, clothing and fashion, decoration, boxes for electronics, telephony, home automation, IT, lighting.

Layer by layer sintering processes require a prior transformation of the PEBAs in the form of powders. These powders must be suitable for use in sintering devices and allow the manufacture of flexible parts with satisfactory mechanical properties.

The quality of the manufactured parts as well as their mechanical properties depend on the properties of the PEBA powder. For example, the agglomeration of powder should be avoided, as it leads to the manufacture of three-dimensional articles having poor definition. In addition, the powder must be able to be conveyed and form a uniform bed, without clumping or forming clusters or crevices. Otherwise, it cannot be transformed correctly. The addition of an additive such as a flow agent can improve flow properties to some extent. However, when a high amount of flow agent is used, the powder coalescing requires a lot of energy, which does not allow to have parts having both good definition and good mechanical properties. In particular, they can reduce the elongation at break of the material

Document FR 2955330 A1 relates to a thermoplastic powder composition with a D50 of less than 100 μm, comprising: at least one block copolymer with a melting point of less than 180 ° C, from 15 to 50% by weight of at least one pulverulent filler Mohs hardness less than 6 and D50 less than 20 µm and 0.1 to 5% of a powder flow agent with D50 less than 20 µm. The document relates in particular to the use of said composition for manufacturing flexible three-dimensional objects. The use of powdered fillers makes it easier to grind and thus obtain the desired particle size. However, the presence of fillers at a high content in the manufactured parts adversely affects their mechanical properties.

EP 0 968 080 A1 relates to a thermoplastic powder comprising a mixture of powdered flow agent and of a powdered block copolymer thermoplastic resin having a glass transition temperature not exceeding 50 ° C. This powder can be used for the manufacture of flexible three-dimensional objects. Document EP 1 845 129 A1 relates to a process for manufacturing shaped articles from polymer powders by layer-by-layer sintering of the powder. The powder comprises at least one block polyetheramide prepared from oligoamide-dicarboxylic acids and polyetherdiamines.

However, there is still a real need to provide a PEBA powder composition allowing the construction of three-dimensional articles by sintering in an efficient manner, in particular allowing to work with a wider working window and at a relatively low construction temperature, said articles. being characterized by good mechanical properties such as good flexibility. There is also a need to provide a PEBA powder composition having good recyclability.

Summary of the invention

The invention relates firstly to a composition comprising a powder of copolymer with polyamide blocks and polyether blocks, the copolymer being in the form of particles having a powdery fillers content of 0 to 10% by mass and the copolymer having a mass ratio of polyamide blocks on polyether blocks less than or equal to 0.7, the polyamide blocks having a number-average molar mass less than or equal to 1000 g / mol; and the composition comprising a flow agent in a content greater than or equal to 0.3% by mass.

According to certain embodiments, the polyamide blocks have a number-average molar mass of less than or equal to 900 g / mol.

According to certain embodiments, the mass ratio of the polyamide blocks to the polyether blocks is less than or equal to 0.65.

According to some embodiments, the flow agent is present at a content of less than or equal to 2% by mass.

According to certain embodiments, the flow agent is chosen from silicas, in particular hydrated silicas, pyrogenic silicas, vitreous silicas and fumed silicas; alumina, especially amorphous alumina; glassy phosphates, glassy borates, glassy oxides, titanium dioxide, calcium silicates, magnesium silicates, talc, mica, kaolin, attapulgite, and mixtures thereof.

According to certain embodiments, the particles of the powder have a size Dv10 greater than or equal to 30 μm and preferably greater than or equal to 35 μm. According to certain embodiments, the particles of the powder have a size Dv90 less than or equal to 250 μm and preferably less than or equal to 200 μm.

According to some embodiments, the particles of the powder have a Dv50 size of 80 to 150 µm, and preferably 90 to 120 µm.

The sizes Dv10, Dv50 and Dv90 are measured according to ISO 13320: 2009, for example by laser diffraction on a Malvern dry diffractometer, and by modeling the distribution of the particles according to ISO 9276.

According to certain embodiments, the copolymer has an instantaneous hardness as measured according to ISO 868: 2003 from 20 to 75 Shore D, and preferably from 25 to 45 Shore D.

According to certain embodiments, the polyamide blocks of the copolymer are blocks of polyamide 11, or of polyamide 12, or of polyamide 6, or of polyamide 10.10, or of polyamide 10.12, or of polyamide 6.10; and / or the polyether blocks of the copolymer are blocks of polyethylene glycol, polypropylene glycol or polytetrahydrofuran.

According to certain embodiments, the polyamide blocks of the copolymer are blocks of polyamide 11, or of polyamide 12, or of polyamide 1010, or of polyamide 1012; and / or in which the polyether blocks of the copolymer are blocks of polyethylene glycol, polypropylene glycol or polytetrahydrofuran.

According to certain embodiments, the polyether blocks have a number-average molar mass of 400 to 3000, preferably 800 to 2200 g / mol.

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

- the supply of a polyamide block and polyether block copolymer and the grinding thereof, and

- bringing the copolymer into contact with a flow agent.

According to some embodiments, the contacting of the copolymer with the flow agent is carried out before grinding.

According to some embodiments, the grinding is cryogenic grinding. In some embodiments, the copolymer is provided in the form of granules.

According to certain embodiments, the particles resulting from the grinding are sieved, the sieve residue being recycled to the grinding. The invention also relates to the use of the composition described above, for the construction of a three-dimensional article layer-by-layer, by sintering caused by electromagnetic radiation.

The invention also relates to a three-dimensional article made from the composition described above, preferably by layer-by-layer construction by sintering caused by electromagnetic radiation.

The present invention makes it possible to meet the need expressed above. It more particularly provides a PEBA powder composition allowing the construction of three-dimensional articles by sintering in an efficient manner, in particular allowing to work with a wider working window and at a relatively low construction temperature, said articles being characterized by good mechanical properties such as good flexibility. The composition according to the invention also exhibits good recyclability.

Thanks to a content of pulverulent fillers in a content of 0 to 10% by mass in the PEBA particles, the three-dimensional articles can be obtained with good mechanical properties, in particular a high elongation at break. In addition, the content of pulverulent fillers less than or equal to 10% by mass makes it possible to obtain three-dimensional articles with good impact resistance. Indeed, the presence of pulverulent fillers in PEBA particles at a content greater than 10% by mass can lead to fragile three-dimensional articles therefore having reduced impact resistance.

In addition, a mass ratio of polyamide blocks to polyether blocks of less than or equal to 0.7 also makes it possible to obtain three-dimensional articles having the desired flexibility properties. Thus, three-dimensional articles made from the composition according to the invention exhibit a relatively low modulus of elasticity.

The presence of an amount greater than or equal to 0.3% by mass of flow agent further improves the flowability of the powder as well as its recyclability while maintaining the good mechanical properties of the three-dimensional articles.

Finally, the fact that the polyamide blocks have a number-average molar mass of less than or equal to 1000 g / mol makes it possible to implement the construction process at a relatively low working temperature, and to have a wide working window. In other words, the fact that the polyamide blocks have a number-average molar mass of less than or equal to 1000 g / mol makes it possible to have a powder composition in which the PEBA copolymer has a relatively low melting temperature, and which is sufficiently distant from the crystallization temperature, which subsequently allows to work in a wide range of construction temperature values.

Moreover, the fact of preferably bringing the PEBA copolymer into contact with the flow agent before the grinding step makes it possible to improve not only the efficiency (or yield) of the grinding but also the recycling of the polymer mixture. flow agent to increase the efficiency of the powder preparation process. More particularly, thanks to the better flowability of this mixture, sieving can be carried out so as to recycle the largest particles to the mill.

detailed description

The invention is now described in more detail and in a non-limiting manner in the description which follows.

Copolvmother

The invention uses a polyamide block (PA) and polyether (PE) block copolymer, or "PEBA" 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.

Preferably, the PEBAs according to the invention are obtained by polycondensation 2) or 3), and preferably by polycondensation 3).

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 from 4 to 20 carbon atoms, preferably those having from 6 to 18 carbon atoms, and from an aliphatic or aromatic diamine. , 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 1, 4-cyclohexyldicarboxylic acid, butanedioic, adipic, azelaic, suberic, sebacic, dodecanedicarboxylic, octadecanedicarboxylic and terephthalic and isophthalic acids, but also dimeric and isophthalic fatty acids. . As examples of diamines, mention may be made of tetramethylene diamine, hexamethylenediamine, 1, 10-decamethylenediamine, dodecamethylenediamine, trimethylhexamethylene diamine, isomers of bis- (4-aminocyclohexyl) -methane (BACM), bis - (3-methyl-4- aminocyclohexyl) methane (BMACM), and 2-2-bis- (3-methyl-4- aminocyclohexyl) -propane (BMACP), para-amino-di-cyclo-hexyl-methane ( PACM), isophoronediamine (IPDA), 2,6-bis- (aminomethyl) -norbornane (BAMN) and piperazine (Pip).

Advantageously, 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 polyamide blocks are used. In the notation of PA-type polyamides 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 a, w-aminocarboxylic acids and / or one or more lactams having from 6 to 12 carbon atoms in the presence of a dicarboxylic acid having from 4 12 carbon atoms or a diamine. Examples of lactams that may be mentioned include caprolactam, enantholactam and lauryllactam. As examples of α, w-amino carboxylic acid, mention may be made of aminocaproic, 7-amino-heptanoic, 1-amino-1-undecanoic and 12-amino-dodecanoic acids.

Advantageously, the polyamide blocks of the second type are blocks of PA 1 1 (polyundecanamide), of PA 12 (polydodecanamide) or of PA 6 (polycaprolactam). In the notation of polyamides of PA X type, X represents the number of carbon atoms resulting from the amino acid (or lactam) residues. 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 of 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, 1-amino-1-undecanoic and 12-amino-dodecanoic acids. As 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 cycloaliphatic diacids, mention may be made of 1, 4-cyclohexyldicarboxylic acid. As examples of aliphatic diacids, mention may be made of butane-dioic, adipic, azelaic, suberic, sebacic, dodecanedicarboxylic acids and dimerized fatty acids. These dimerized fatty acids preferably have a dimer content of at least 98%; preferably they are hydrogenated; it's about for example 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 cycloaliphatic diamines, mention may be made of the isomers of bis- (4-aminocyclohexyl) - methane (BACM), bis- (3-methyl-4-aminocyclohexyl) methane (BMACM) and 2-2-bis- (3-methyl-4-aminocyclohexyl) -propane (BMACP), and para-amino-di-cyclo-hexyl-methane (PACM). Other commonly used diamines can be isophoronediamine (IPDA), 2,6-bis- (aminomethyl) - norbornane (BAMN) and piperazine.

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 66/610/1 1/12, where 66 denotes hexamethylenediamine condensed with adipic acid, 610 denotes hexamethylenediamine condensed with sebacic acid, 1 1 denotes units resulting from the condensation of the acid aminoundecanoic 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 up of alkylene oxide units.

The polyether blocks can in particular be PEG (polyethylene glycol) blocks, that is to say made up of ethylene oxide units, and / or PPG (propylene glycol) blocks, in other words made up of propylene oxide units, and / or or P03G (polytrimethylene glycol) blocks, that is to say made up of polytrimethylene glycol ether units, and / or PTMG blocks, that is to say 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

H

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 trademark NORAMOX® from the company CECA and under the brand GENAMIN® from the company CLARIANT.

The polyether blocks can comprise polyoxyalkylene blocks having 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 148201 1).

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 148201 1. The polyether blocks can also be mixed with polyamide precursors and a diacid chain limiter to prepare the polymers comprising 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 "triblocks"), 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 1 1 and PEG;

- PA 1 1 and PTMG;

- PA 12 and PEG;

- PA 12 and PTMG;

- PA 610 and PEG;

- PA 610 and PTMG;

- PA 1010 and PEG;

- PA 1010 and PTMG;

- PA 1012 and PEG;

- PA 1012 and PTMG;

- PA 6 and PEG;

- PA 6 and PTMG.

The number-average molar mass of the polyamide blocks in the PEBA copolymer is less than or equal to 1000 g / mol, and preferably less than or equal to 900 g / mol.

Thus, the polyamide blocks in the PEBA copolymer can have a number-average molar mass of 100 to 200 g / mol; or from 200 to 300 g / mol; or from 300 to 400 g / mol; or from 400 to 500 g / mol; or from 500 to 600 g / mol; 600-700 g / mol; or from 700 to 800 g / mol; or 800 to 900 g / mol; or from 900 to 1000 g / mol.

In certain embodiments, the number-average molar mass of the polyether blocks in the PEBA copolymer is from 250 to 2000 g / mol, preferably from 400 to 2000 g / mol, and for example more preferably from 800 to 1500 g / mol.

Thus, the polyether blocks in the PEBA copolymer can have a number-average molar mass of 250 to 300 g / mol; or from 300 to 400 g / mol; or from 400 to 500 g / mol; or from 500 to 600 g / mol; or from 600 to 700 g / mol; or from 700 to 800 g / mol; or 800 to 900 g / mol; or from 900 to 1000 g / mol; or 1000 to 1500 g / mol; or from 1500 to 2000 g / mol.

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

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

In this formula, nmonomer represents the number of moles of monomer, chain niimiter represents the number of moles of excess chain limiter (e.g. diacid), MW repeat unit represents the molar mass of the repeat unit, and MW chain limiter represents the molar mass of the excess chain 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 permeation chromatography (GPC).

The mass ratio of the polyamide blocks relative to the polyether blocks of the PEBA copolymer is less than or equal to 0.7, and preferably less than or equal to 0.65. 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 polyether blocks.

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 0.6; or from 0.6 to 0.7.

Preferably, the copolymer used in the invention has an instantaneous hardness of 20 to 75 Shore D, and preferably of 25 to 45 Shore D. The hardness measurements can be carried out according to the ISO 868: 2003 standard.

The practice of the invention is particularly advantageous with a relatively flexible PEBA copolymer, since the particles of such a copolymer have an increased tendency to agglomeration.

The PEBA copolymer can have a glass transition temperature less than or equal to 0 ° C, preferably less than or equal to -20 ° C, again preferably less than or equal to -40 ° C, and even more preferably less than or equal to -50 ° C. This temperature is measured by dynamic mechanical analysis (DMA) according to the ISO 6721-1 1: 2012 standard.

Process for manufacturing the co-polymer powder

The method according to the invention firstly comprises providing a PEBA copolymer as described above. According to some embodiments, it is possible to use a mixture of two or more PEBA copolymers as described above. However, it is preferred to use a single PEBA copolymer as described above. The PEBA copolymer (s) can for example be in the form of granules. Alternatively, the PEBA copolymer (s) may be in the form of scales or a coarse powder, for example having a Dv50 size greater than 250 μm.

The PEBA copolymer is then contacted with a flow agent to form a mixture - preferably before the grinding step.

By "flow agent" is meant an agent which improves the flowability as well as the leveling of the copolymer powder during the sintering process. The flow agent can be chosen from those commonly used in the field of sintering polymer powders. Preferably, this flow agent is of substantially spherical shape. It is, for example, chosen from silicas, in particular hydrated silicas, pyrogenic silicas, vitreous silicas and fumed silicas; alumina, especially amorphous alumina; glassy phosphates, glassy borates, glassy oxides, titanium dioxide, calcium silicates, magnesium silicates, talc, mica, kaolin, attapulgite, and mixtures thereof.

The flow agent is in the form of particles having an average size (Dv50) of 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 10µm.

In the context of this request:

- the Dv10 corresponds to the particle size threshold for which 10% of the particles (by volume) have a size below the threshold, and 90% of the particles (by volume) have a size above the threshold;

- the Dv50 corresponds to the threshold of the particle size 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 Dv10, the Dv50 and the Dv90 are measured according to ISO 13320: 2009, for example by laser diffraction on a Malvern dry diffractometer, and the distribution of the particles is modeled according to the ISO 9276 standard - parts 1 to 6: "Representation of data obtained by particle size analysis ”. The flow agent is added to the PEBA copolymer in a proportion greater than or equal to 0.3% by mass relative to the total weight of the final composition.

The flow agent added to the copolymer may have a content of less than or equal to 3% by mass relative to the total weight of the final composition, preferably less than or equal to 2% by mass. Thus, the flow agent can be added in an amount of 0.3 to 0.4%; or from 0.4 to 0.5%; or from 0.5 to 0.6%; or from 0.6 to 0.7%; or from 0.7 to 0.8%; or from 0.8 to 0.9%; or from 0.9 to 1%; or from 1 to 1, 1%; or from 1.1 to 1.2%; or from 1.2 to 1.3%; or from

1.3 to 1.4%; or from 1.4 to 1.5%; or from 1.5 to 1.6%; or from 1.6 to 1.7%; or from

1.7 to 1.8%; or from 1.8 to 1.9%; or from 1.9 to 2%; or from 2 to 2.5%; or 2.5 to 3.0%.

The PEBA copolymer, preferably premixed with the flow agent, then undergoes a grinding step in order to obtain a powder of the desired particle size.

Preferably, the grinding is cryogenic grinding. Thus, first of all, the mixture of copolymer and flow agent is cooled to a temperature below the glass transition temperature of the copolymer. This temperature can be 10 to 50 ° C lower than the glass transition temperature of the copolymer. 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. This temperature can be -10 to -20 ° C; or from -20 to -30 ° C; or at -30 to -40 ° C; or from -40 to -50 ° C; or from -50 to -60 ° C; or from -60 to -70 ° C; wave -70 to -80 ° C; or from -80 to -90 ° C; or from -90 to -100 ° C.

The cooling of the mixture of copolymer and flow agent can be carried out, for example, with liquid nitrogen, or with liquid carbon dioxide or with dry ice, or with liquid helium.

Preferably the grinding step is carried out in a mill with counter-rotating pins (pin mill). Thus, the crusher comprises a first series of brushes rotating in one direction and a second series of rotating brushes. in the opposite direction. This increases the speed and therefore the energy of the impact. Preferably, these pins can be grooved which allows a greater impact on the particles to be ground.

Alternatively, the grinding step can be performed in a hammer mill or in a whirl mill.

The mill used may include a screen onto which the ground particles are directed. The screen has pores (grid openings) allowing the retention of particles larger than the screen pores on one side and the passage of particles smaller than the screen pores on the other side. When the pores do not have a circular opening, the term "diameter" of the pores is understood to mean the maximum distance between two points lying in a plane parallel to the opening. For example, for pores having a rectangular or square opening, the diameter refers to the diagonal of each opening. The sieve may for example have pores with a diameter less than or equal to 300 μm, or to 250 μm, and preferably less than or equal to 200 μm. The diameter of the pores can be, for example, 100 to 120 µm, 120 to 150 µm; or from 150 to 200 µm; or from 200 to 250 µm; or from 250 to 300 µm.

Thus, particles larger in size than that desired for the preparation of the powder can be retained on the sieve while particles of suitable particle size can pass through the sieve.

The particles retained on the screen can then be led to the mill so that they are recycled and undergo further crushing. Preferably, the recycling of the particles is continuous during the grinding step.

Preferably, a single grinding step is performed.

After grinding, a certain particle size fraction of the powder can be selected, to obtain the desired particle size profile in the invention. Thus, the powders are dispersed by a selection wheel and transported by a classification 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 may have several successive wheels working in parallel.

PEBA powder composition

The composition according to the invention comprises particles of PEBA copolymer and particles of the flow agent. The particles of the composition according to the invention may have a size Dv10 greater than or equal to 30 μm, and preferably greater than or equal to 35 μm. For example, the size Dv10 of the particles of the composition can be 30 to 35 µm; or from 35 to 40 µm; or from 40 to 45 µm; or from 45 to 50 pm.

A Dv10 size greater than or equal to 30 µm avoids the problems related to the density as well as the flowability of the powder. Thus, advantageously the use of a powder of the particles having a size Dv10 greater than or equal to 30 μm makes it possible to obtain a bed of powder of good quality and consequently articles having a good definition of the edges and of the contours.

The use of a powder having a size Dv10 greater than 30 µm allows lower agglomeration of the powder in a three-dimensional printing machine and therefore better recycling.

The amount of flow agent in the composition can be adjusted depending on the particle size of the powder. Generally, the lower the Dv10 of the powder, the greater the amount of flow agent in the powder must be in order to preserve the flowability and mechanical properties of the manufactured parts.

The particles of the composition according to the invention can also have a size Dv90 less than or equal to 250 μm, and preferably less than or equal to 200 μm. For example, the Dv90 size of the particles of the composition can be from 150 to 160 µm; or from 160 to 170 µm; or from 170 to 180 µm; or from 180 to 190 µm; or from 190 to 200 µm; or from 200 to 210 µm; or from 210 to 220 µm; or from 220 to 230 µm; or from 230 to 240 µm; or from 240 to 250 µm.

A Dv90 size of less than or equal to 250 µm also enables articles with good definition of edges and contours to be obtained. Indeed, particles with a Dv90 size greater than 250 µm could lead to articles having poor definition given the layer thickness that is used during the sintering process.

In addition, the particles of the composition according to the invention may have a Dv50 size of 80 to 150 µm, and preferably of 100 to 150 µm. For example, the size Dv50 of the particles of the composition can be 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 1 10 to 1 15 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.

The composition according to the invention may comprise the PEBA copolymer (s) in a proportion by weight preferably greater than or equal to 80%, or at 81%, or 82%, or 83%, or 84%, or 85%, or 86%, or 87%, or 88%, or 89%, or 90%, or at 91%, or at 92%, or at 93%, or at 94%, or at 95%, or at 96%, or at 97%, or at 98%, or at 99%, or at 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%.

The flow agent is present in the composition at a content greater than or equal to 0.3% by weight of the composition. Preferably, the flow agent present in the composition may have a content of less than or equal to 2% by weight of the composition. Thus, this content can be from 0.3 to 0.4%; or from 0.4 to 0.5%; or from 0.5 to 0.6%; or from 0.6 to 0.7%; from 0.7 to 0.8%; or from 0.8 to 0.9%; or from 0.9 to 1%; or from 1 to 1, 1%; or from 1.1 to 1.2%; or from 1.2 to 1.3%; or from 1.3 to 1.4%; or from 1.4 to 1.5%; or from 1.5 to 1.6%; or from 1.6 to 1.7%; or from 1.7 to 1.8%; or from 1.8 to 1.9%; or from 1.9 to 2%.

The PEBA powder in the composition can have an apparent specific surface area of less than 2 m ² / g.

The PEBA particles in the composition can comprise pulverulent fillers at a content of 0 to 10% by weight of the composition. When they are present, these pulverulent fillers can be integrated into the PEBA particles by compounding, in particular at the stage of manufacturing the granules intended to be crushed.

The composition can therefore further comprise from 0 to 10% by weight of pulverulent fillers, relative to the total weight of the composition.

The term “pulverulent filler” means a compound in powder form with an average size (Dvso) greater than 10 μm, in particular greater than 20 μm, which makes it possible to modify the mechanical properties (for example modulus, elongation at break, strength. impact) of the manufactured three-dimensional parts.

Examples of powdery fillers are carbonated mineral fillers, especially calcium carbonate, magnesium carbonate, dolomite, calcite, barium sulfate, calcium sulfate, dolomite, aluminum hydrate, wollastonite , montmorillonite, zeolite, perlite, organic fillers 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 such polymer powders of modulus greater than 1000 MPa. According to certain preferred embodiments, the PEBA particles of the composition of the invention are devoid of pulverulent fillers.

According to certain preferred embodiments, the composition according to the invention is devoid of pulverulent fillers.

Alternatively, if pulverulent fillers are present in the PEBA particles, they are present at a mass content of less than or equal to 10%, preferably less than or equal to 5%, more preferably less than or equal to 1%. For example, the pulverulent fillers can be present in the particles of PEBA at a content by weight of 0.05 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 6%; or from 6 to 7%; or from 7 to 8%; or from 8 to 9%; or 9 to 10%.

The total mass content of pulverulent fillers (when they are present) in the composition (including those present where appropriate in the PEBA particles) is preferably less than or equal to 10%, preferably less than or equal to 5%, more preferably less than or equal to 1%.

The composition according to the invention can comprise, in addition to the flow agent and the pulverulent fillers already mentioned, any type of other suitable additive for the polymer powders used in sintering: in particular additives (in powder form or not) which contribute to improving the properties of the powder for its use in agglomeration technology and / or additives making it possible to improve the properties, for example aesthetic (color) of objects obtained by fusion. The composition of the invention can in particular comprise dyes, pigments for coloring, PO2, pigments for infrared absorption, carbon black, anti-fire additives, glass fibers, carbon fibers, etc. The composition of the invention can also contain at least one additive chosen from antioxidant stabilizers, light stabilizers, anti-shock agents, antistatic agents, flame retardants, and mixtures thereof. These additives are preferably in the form of a powder having a Dv50 of less than 20 μm, and in particular less than 10 μm. Advantageously, the additives in powder form have a Dv greater than 100 nm, and very particularly greater than 1 μm.

These additives can be present in the composition at a mass content of 0.05 to 5%.

Preferably the additives comprise one or more pigments.

The additives can be mixed with the PEBA copolymer before and / or after the grinding step described above. In certain embodiments, the powder composition can have a polyamide block crystallization temperature of 40 to 160 ° C, and preferably 50 to 100 ° C. The composition can in particular have a polyamide block crystallization temperature of 40 at 50 ° C; or from 50 to 60 ° C; or from 60 to 70 ° C; or from 70 to 8 C to 90 ° C; or from 90 to 100 ° C; or from 100 to 110 ° C; or 1 10 120-130 ° C; or from 130 to 140 ° C; or from 140 to 150 ° C; or from 150 to 160 ° C The crystallization temperature can be measured by differential scanning calorimetry according to standard ISO 1 1357-3.

The PEBA copolymer can have a melting point of less than or equal to 150 ° C, and preferably of less than or equal to 140 ° C. The PEBA copolymer can in particular have a melting point of 100 to 105 ° C; or from 105 to 110 ° C; or from 110 to 115 ° C; or from 115 to 120 ° C; o from 120 to 125 ° C; or from 125 to 130 ° C; or from 130 to 135 ° C; or 135-140 ° C or 140-145 ° C; or 145 to 150 ° C. The melting temperature can be measured by differential scanning calorimetry according to the ISO 1 1357-3 standard.

A melting temperature of 150 ° C or less can decrease the heating time as well as the energy consumption during the process of constructing three-dimensional articles layer-by-layer by sintering, thus improving the performance. efficiency of the process for preparing such articles. The difference between the crystallization temperature and the melting temperature is preferably greater than or equal to 30 ° C, more preferably greater than or equal to 40 ° C, or to 50 ° C, or to 60 ° C, or to 70 ° C, or âO ° C.

The powder composition according to the invention can have a flowability of 2 to 10 seconds. The flowability can be measured according to ISO 6186: 1998 (E) Method A; 25 mm hole at 23 ° C.

Powder sintering process

PEBA powder, as described above, is used for a method of constructing three-dimensional articles layer-by-layer by sintering caused by electromagnetic radiation.

The electromagnetic radiation can be, for example, infrared radiation, ultraviolet radiation, 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 "construction temperature" denotes the temperature at which the bed of powder, of a constituent layer of a three-dimensional object under construction, is heated during the layer-by-layer sintering process of the powder. This temperature may be lower than the melting point of the PEBA copolymer by less than 100 ° C, preferably less than 40 ° C, and more preferably around 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 layer of powder, and a new layer is deposited. The electromagnetic radiation provides the energy required to sinter the powder particles in 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.

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 recycled or not.

Thus, the powder composition can be recycled (i.e. used in more than one construction) once, or twice, or three times, or four times, or five times, or more than five times.

The three-dimensional articles manufactured may exhibit an elongation at break greater than or equal to 200%, preferably greater than or equal to 400%, and more preferably greater than or equal to 500%. By "elongation at break" is meant the ability of a material to elongate before breaking when stressed in tension. The elongation at break can be measured according to ISO 527 1 A.

The three-dimensional articles manufactured can advantageously have a modulus of elasticity less than or equal to 100 MPa and more preferably less than or equal to 70 MPa, or to 50 MPa; it can be, for example, from 1 to 100 MPa; preferably from 10 to 70 MPa. The modulus of elasticity can be measured according to ISO 527 1: 2019. 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. Examples

The following examples illustrate the invention without limiting it. Unless otherwise indicated, the percentages indicated refer to percentages by weight relative to the entire formulation. Example 1

In this example, a PEBA copolymer powder (blocks of PA1 1 of 600 g / mol, blocks of PTMG of 1000 g / mol, mass ratio PA1 1 / PTMG = 0.6, Tm = 135 ° C, formulated with 0.8% by weight of sfebilizing additives) having a Dv10 size of 21 µm, a Dv50 size of 48 µm, and a Dv90 size of 100 µm (free of fillers) is mixed in a rapid mixer at different mass rates of flow agent next :

Agent 1: fumed silica with an average size of less than 0.1 - 0.3 μm and a specific surface area of 50 m ² / g (dimethyldichlorosilane treatment, TS610 marketed by the Cabot Corporation),

Agent 2: fumed silica with an average size of less than 1 μm and a specific surface area of 220 m ² / g (CT1221 marketed by the company Cabot Corporation), and

Agent 3: pyrogenic alumina with an average size of 7 to 40 nm and a specific surface area greater than 50 m ² / g (BET) (Alumina C marketed by the company Evonik).

The flowability of these mixtures with holes of 25 mm and 15 mm diameters as well as the apparent and packed densities are measured (flowability according to standard ISO 6186: 1998 (E) Method A, 23 ° C, packing volume meter to DIN standards ISO 787 Part 1 1: 1981, 2500 steps on the graduated cylinder for the packed density).

[Table 1]

NCP = Do Not Sink

It is found that mixtures having a flow agent level greater than or equal to 0.3% by mass give better results. More particularly, good flowability can be characterized in particular by flowability through a funnel with a diameter of 15 mm and a funnel with a diameter of 25 mm, which makes it possible to have a good supply of the powder. This also allows for sufficient spread to obtain a good quality powder bed before and during sintering as well as sufficient flow to fill the cavities of the parts after laser passage. Mixtures with a flow agent level greater than or equal to 0.3% by mass also improve the bulk and packed density, compared to PEBA powder alone. Example 2

In this example, a PEBA powder (same characteristics as in Example 1) but having a Dv10 size of 42 µm, a Dv50 size of 106 µm and a Dv90 size of 178 µm (devoid of fillers) is mixed in a rapid mixer. at different levels by mass of a flow agent (TS610 marketed by the company Cabot Corporation).

[Table 2]

It is observed that when the PEBA copolymer powder has, as in this example, a Dv10 size greater than 30 μm, a Dv50 size between 50 and 150 μm and a Dv90 size less than 250 μm, the flow capacity as well as the density apparent and packed is also improved compared to a single PEBA powder.

Example 3

In this example, a PEBA powder (same characteristics as in Example 1) and 0.3% by weight of a flow agent (TS610 marketed by Cabot Corporation) are mixed. The flow agent is added to the PEBA granules before grinding, to obtain the powder. The powder obtained has a Dv10 of 24 µm, a Dv50 of 73 µm and a Dv90 of 217 µm (Composition A). A selection was then carried out on a CFS 5 HD-S selector (Netzsch) with an incoming flow rate of 2 kg / h and by fixing a speed of rotation such that a powder is obtained with a Dv10 of 38 μm, a Dv50 of 88 µm and a Dv90 of 231 µm (Composition B).

The following test was carried out on the two compositions and the results are illustrated in Table 3 below. The two compositions are poured in the same way into two metal cylinders with a diameter of 5 cm and a height of 3 cm. The cylinders containing the compositions are then placed in an oven for 4 h at a temperature below the melting point of the PEBA copolymer of 20 ° C. (115 ° C.). The cylinders are taken out of the oven and left to cool to room temperature (23 ° C) for 4 h.

A 1 mm diameter needle ballasted with a weight of 500 g is then dropped at various places on the surface of the powder. By measuring the depth to which the needle goes, the cohesion of the powders can be assessed after the 4 hours at a temperature below the melting temperature of the PEBA copolymer of 20 ° C and the 4 hours of cooling to room temperature. The less the needle goes in and the more the powder has stuck with itself in the oven, the more difficult it will be to recycle.

[Table 3] It is observed that the needle sinks deeper into composition B having a Dv10 greater than 30 μm, which means that this powder sticks less and that it will therefore be easier to recycle it.

Example 4

PEBA granules devoid of fillers (blocks of PA12 of 850 g / mol, blocks of PTMG of 2000 g / mol, mass ratio PA12 / PTMG = 0.425, formulated with 0.2% by weight of stabilizing additives) are ground with Mikropul 2DH , hammer mill, under cryogenic conditions. This powder composition (C) obtained after grinding has a Dv10 size of 66 µm, a Dv50 size of 157 µm, and a Dv90 size of 292 µm.

Likewise, the same granules of PEBA premixed with 1.0% by mass of flow agent (TS610 marketed by Cabot Corporation) are introduced into the mill under the same conditions. This powder composition (D) obtained after grinding has a Dv10 size of 60 µm, a Dv50 size of 137 µm, and a Dv90 size of 247 µm. It is found that the powder composition D has a reduced Dv90 compared to the powder composition C.

Example 5

The following powders are tested:

- EC1 (comparative): PA12 powder (PEBA 2301 Primepart ST sold by EOS).

- EC2 (comparative): PEBA PA12 / PPG powder with a PA12 block size of 1068 g / mol, a PPG block size of 2000 g / mol, and a PA12 / PPG ratio of approximately 0.53.

- EC3 (comparative): PEBA PA12 / PEG powder with a PA12 block size of 1500 g / mol, a PEG block size of 1500 g / mol, and a PA12 / PEG ratio of 1.

- EC4 (comparative): PEBA PA12 / PTMG powder with a PA12 block size of 1000 g / mol, a PTMG block size of 1000 g / mol, and a PA12 / PTMG ratio of 1.

- EC5 (comparative): PEBA PA1 1 / PTMG powder with a PA1 1 block size of 1000 g / mol, a PTMG block size of 1000 g / mol and a PA1 1 / PTMG ratio of 1. - E1 (invention): PEBA PA12 / PTMG powder with a PA12 block size of 850 g / mol, a PTMG block size of 2000 g / mol and a PA12 / PTMG ratio of 0.43.

- E2 (invention): PEBA PA11 / PTMG powder with a PA11 block size of 600 g / mol, a PTMG block size of 1000 g / mol, and a ratio

PA1 1 / PTMG of 0.6.

- E3 (invention): PEBA PA12 / PTMG powder with a PA12 block size of 600 g / mol, a PTMG block size of 2000 g / mol and a PA12 / PTMG ratio of 0.3.

- E4 (invention): PEBA PA1 1 / PTMG powder with a PA11 block size of 600 g / mol, a PTMG block size of 2000 g / mol and a PA1 1 / PTMG ratio of 0.3.

PEBAs based on PA 12 are formulated with 0.2% by weight of stabilizing additives, those based on PA1 1 with 0.8% by weight of stabilizing additives. All these powders are free of charge.

The analysis of differential scanning calorimetry (DSC) at 20 ° C / min (standard conditions) of these powders, as well as a measurement of the modulus of elasticity of parts manufactured by injection from these powders gave the following results :

[Table 4]

It is observed that when the mass ratio of the polyamide blocks to the polyether blocks in the PEBA is less than or equal to 0.7 and when the polyamide blocks have a number-average molar mass less than or equal to 1000 g / mol (E1 to E4), the melting temperatures of the PEBA copolymer are lower (compared to EC1 to EC5) and sufficiently far from the crystallization temperatures, which subsequently allows to work in a wide range of values construction temperature, in a layer-by-layer construction process.

It is also noted that the tensile moduli measured on an injected part obtained are less than 50 MPa, which means that the powders of the invention confer good mechanical properties and in particular good flexibility.

The modulus is measured according to the ISO 527-1 / 2 standard.

The moduli of the sintered parts can vary from those of the injected parts. This is due to greater crystallization of sintered three-dimensional objects which remain between Tf and Te longer than when injected. However, the relative comparison of the moduli of elasticity obtained by injection is representative of the relative comparison of the moduli of elasticity obtained by sintering. The invention thus makes it possible to obtain three-dimensional articles having moduli of elasticity less than or equal to 70 MPa (preferably 50 MPa). Example 6

A PEBA powder (with PA11 blocks of size 600 g / mol, PTMG blocks of size 1000 g / mol and a PA1 1 / PTMG mass ratio of 0.6) having a Dv10 size of 42 µm, a Dv50 size of 106 µm, and a Dv90 size of 178 µm, free of fillers and additive of flow agent (TS610 marketed by Cabot Corporation) is sieved at 160 µm before undergoing a sintering process by passing through an EOS machine Formiga P100. Test pieces are produced at a construction temperature of 103.5 ° C. and with a laser energy of 350 mJ / mrri ³ , which makes it possible to obtain good definition as well as optimum mechanical properties. The powder from the bed which has not been touched by the electromagnetic radiation is, after cooling, again sieved at 160 pm.

The results are shown below:

[Table 5]

It is noted that the addition of 0.2% by mass of flow agent does not allow good recyclability of the powder. However, when the flow agent is added at a content greater than or equal to 0.3% by mass, the powder will agglomerate less and the recyclability of the powder thus increases significantly. The addition of 1 wt% flow agent achieves the full maximum recyclability of the powder.

Example 7

A laser sintering process is carried out on an EOS Formiga P100 machine (construction temperature of 103.5 ° C, laser energy of 350 mJ / mm ³ ) with the PEBA powder of example 6. One obtains 1 BA test pieces for carry out tensile tests and test specimens to measure the Charpy impact strength at room temperature and at -30 ° C, notched after sintering.

The results are shown below:

[Table 6]

The elongation at break was measured according to ISO 527-2 1 BA.

The Charpy impact resistance measurement was carried out according to the ISO 179/1 eA standard (at 23 ° C and at -30 ° C).

It is found that the presence of the flow agent in an amount of 0.3 to 1.0% by mass does not adversely affect the mechanical properties of the parts obtained by laser sintering. Example 8

PEBA granules (same characteristics as in Example 1) are compounded with 20% by mass of dolomite as a pulverulent filler and then ground with a Mikropul 2DH, hammer mill, and then the powder is sieved at 160 µm. The powder has a Dv10 size of 33 µm, a Dv50 size of 62 µm, and a Dv90 size of 11 1 µm.

A similar powder is produced without compounding with fillers.

0.3% by mass of a flow agent (TS610) is then added to the two powders obtained.

A sintering process was carried out from these powders, on a Formiga P100 machine (sold by the company EOS) under optimized conditions (construction temperature of 105 ° C., laser energy of 350 mJ / mm ³ ).

The results are shown below:

[Table 7]

It is found that when powder fillers are present in the PEBA particles in a significant content, the three-dimensional articles are obtained with deteriorated mechanical properties, in particular with a reduced elongation at break compared to a three-dimensional article obtained from a composition not comprising pulverulent fillers in the PEBA particles.

Claims

1. Composition comprising a powder of copolymer containing polyamide blocks and polyether blocks, the copolymer being in the form of particles having a powdery fillers content of 0 to 10% by mass and the copolymer having a lower mass ratio of polyamide blocks to polyether blocks or equal to 0.7, the polyamide blocks having a number-average molar mass of less than or equal to 1000 g / mol; and the composition comprising a flow agent in a content greater than or equal to 0.3% by mass.

2. Composition according to claim 1, in which the polyamide blocks have a number-average molar mass of less than or equal to 900 g / mol.

3. Composition according to one of claims 1 to 2, wherein the mass ratio of the polyamide blocks to the polyether blocks is less than or equal to 0.65.

4. Composition according to one of claims 1 to 3, wherein the flow agent is present at a content of less than or equal to 2% by mass.

5. Composition according to one of claims 1 to 4, in which the flow agent is chosen from silicas, in particular hydrated silicas, pyrogenic silicas, vitreous silicas and fumed silicas; alumina, especially amorphous alumina; glassy phosphates, glassy borates, glassy oxides, titanium dioxide, calcium silicates, magnesium silicates, talc, mica, kaolin, attapulgite and mixtures thereof.

6. Composition according to one of claims 1 to 5, in which the particles of the powder have a size Dv10 greater than or equal to 30 μm and preferably greater than or equal to 35 μm.

7. Composition according to one of claims 1 to 6, in which the particles of the powder have a size Dv90 of less than or equal to 250 μm and preferably less than or equal to 200 μm.

8. Composition according to one of claims 1 to 7, in which the particles of the powder have a Dv50 size of 80 to 150 μm, and preferably of 90 to 120 μm.

9. Composition according to one of claims 1 to 8, wherein the copolymer has an instantaneous hardness of 20 to 75 Shore D, and preferably of 25 to 45 Shore D.

10. Composition according to one of claims 1 to 9, in which the polyamide blocks of the copolymer are blocks of polyamide 11, or of polyamide 12, or of polyamide 6, or of polyamide 1010, or of polyamide 1012, or of polyamide 610; and / or in which the polyether blocks of the copolymer are blocks of polyethylene glycol, polypropylene glycol or polytetrahydrofuran.

1 1. Composition according to one of claims 1 to 10, in which the polyamide blocks of the copolymer are blocks of polyamide 11, or of polyamide 12, or of polyamide 1010, or of polyamide 1012; and / or in which the polyether blocks of the copolymer are blocks of polyethylene glycol, polypropylene glycol or polytetrahydrofuran.

12. Composition according to one of claims 1-1 1, wherein the polyether blocks have a number-average molar mass of 400 to 3000, preferably 800 to 2200 g / mol.

13. A method of preparing the composition according to one of claims 1 to 12, comprising:

- bringing the copolymer into contact with a flow agent.

14. The method of claim 13, wherein the contacting of the copolymer with the flow agent is carried out before grinding.

15. A method according to one of claims 13 or 14, wherein the grinding is cryogenic grinding.

16. A method according to one of claims 13 to 15, wherein the copolymer is supplied in the form of granules.

17. The method of claim 13 to 16, wherein the particles resulting from the grinding are sieved, the sieve residue being recycled to the grinding.

18. Use of the composition according to one of claims 1 to 12, for the construction of a three-dimensional article layer-by-layer, by sintering of the composition caused by electromagnetic radiation.

19. A three-dimensional 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.