Filled polyaryletherketone powder, its production method and use

Abstract

The present invention relates to a powder having a volume-weighted particle size distribution with a median diameter D50 in the range of 40 to 120 micrometers, comprising at least one polyaryletherketone and at least one filler, - the at least one polyaryletherketone at least partially forming a matrix incorporating said at least one filler, - the filler having a distribution of equivalent sphere diameters (according to Stokes' law) with a median diameter less than 50 micrometers or equal to 5 micrometers. The invention further relates to a method for producing the powder and to its use in a method for layer-by-layer fabrication of objects by electromagnetic radiation-mediated induced sintering. TIFF2022551877000012.tif136170

Description

[Technical Field]

[0001] The present invention relates to the field of polyaryletherketone powders.

[0002] More particularly, the present invention relates to filled polyaryletherketone powders, methods for their manufacture, and their use in methods for manufacturing three-dimensional objects, especially electromagnetic radiation mediated powder sintering methods. [Background technology]

[0003] Polyaryletherketones (PAEKs) are well-known, high-performance technical polymers. They can be used in applications that are constrained in terms of temperature and / or mechanical and even chemical limitations. They can also be used in applications requiring excellent fire resistance and low emissions of fumes or toxic gases. Finally, they have good biocompatibility. These polymers are found in diverse fields such as the aerospace sector, offshore drilling, automotive, rail, maritime, wind power, sports, construction, electronics, or medical implants. They can be used in all techniques where thermoplastics are used, such as molding, compression, extrusion, spinning, powder coating, or sintered prototyping.

[0004] The process of layer-by-layer construction of objects by sintering mediated by electromagnetic radiation, particularly infrared and laser radiation, is well known to those skilled in the art. Referring to FIG. 1 , a laser sintering device 1 comprises a sintering chamber 10 in which a supply tank 40 containing powder to be sintered is placed, a horizontal plate 30 supporting a three-dimensional object 80 to be built, and a laser 20. The powder is taken from the supply tank 40 and deposited on the horizontal plate 30 to form a thin layer 50 of powder that constitutes the three-dimensional object 80 to be built. A compaction roller / doctor blade (not shown) ensures good uniformity of the powder layer 50. Under build, the powder layer 50 is heated by infrared radiation 100 to reach a substantially uniform temperature equal to a predetermined build temperature, Tc. In conventional PAEK-based powder sintering build processes, Tc is typically about 20°C below the melting point of the powder. In certain cases, Tc is even lower. The energy required to sinter the powder particles at various points in the powder bed 50 is provided by laser radiation 200 from a laser 20 that can move in a plane (x-y) in a geometry corresponding to the geometry of the object. The molten powder resolidifies to form a sintered part 55, leaving the remainder of the layer 50 as green powder 56. In certain cases, multiple passes of the laser radiation 200 may be required. The horizontal plate 30 is then lowered along the axis (z) a distance corresponding to the thickness of one layer of powder, and a new layer is deposited. The laser 20 provides the energy required to sinter the powder particles in a geometry corresponding to the new slice of the object, and the process continues. This procedure is repeated until the entire object 80 is produced. Once the object 80 is completed, it is removed from the horizontal plate 30, and the green powder 56 is sieved, if appropriate, and returned to the supply tank 40 as recycled powder.

[0005] It is known practice to add carbon fibers to polyaryletherketone powders in order to improve the mechanical properties, in particular to increase the modulus of elasticity, of objects made from the polyaryletherketone powders, in particular objects made by electromagnetic radiation-mediated sintering.

[0006] Carbon fibers may be dry-mixed with polyaryletherketone particles. For example, U.S. Patent Application Publication No. 2018 / 0201783 describes a composition obtained by dry-blending polyetherketoneketone particles with carbon fibers having a median length strictly greater than the average particle diameter. More specifically, the resulting blend contains 85% by weight of polyetherketoneketone particles having a median diameter of 61.34 μm, as measured using a Coulter Counter particle counter according to standard ISO 13319, and 15% by weight of carbon fibers having a median length L50 equal to 77 μm and an approximate diameter equal to 7.1 μm. The blend is introduced into a high-intensity mixer to partially incorporate at least some of the carbon fibers into the polyetherketoneketone particles. Dry blends of polyetherketoneketone particles and carbon fibers have the advantage of being particularly easy to prepare.

[0007] Dry blending of carbon fibers with polyaryletherketone particles has several drawbacks.

[0008] The first drawback is that the three-dimensional objects obtained from laser sintering of these powders have anisotropic mechanical properties, i.e., they differ depending on whether the object is viewed along the Z axis along which the various layers are printed, or along the XY plane along which each layer is printed. The reason for this is that carbon fibers have a tendency to align along a preferred direction during the passage of the compaction roller / doctor blade.

[0009] A second drawback is that it is not possible to use a high proportion of carbon fiber in the powder, as this would impair the powder's flowability and thus the good flowability required for use in laser sintering. Specifically, given that carbon fiber is very difficult to incorporate into polyetherketoneketone particles, a high proportion of carbon fiber in the composition will only entrain a low proportion that is sufficiently incorporated into the polyetherketoneketone particles. This means that most of the carbon fiber remains in the composition, thus impairing the powder's flowability. In addition, powder freshening, i.e., at least partial reuse, for the creation of another object by laser sintering after screening cannot be easily achieved due to the difficulty of maintaining a constant carbon fiber content in the polyetherketoneketone powder. US Patent Application Publication No. 2018 / 0201783 suggests a proportion of carbon fiber in the dry blend ranging from 5% to 30% by weight, bearing in mind that currently, dry blends of polyetherketoneketone particles with commercially available carbon fiber have a proportion of carbon fiber of less than 15% by weight of the composition.

[0010] Powders in which carbon fibers are incorporated into polyaryletherketone particles are known, so that three-dimensional objects obtained by laser sintering have substantially isotropic mechanical properties. For example, U.S. Patent Application Publication No. 2005 / 0207931 describes polyetheretherketone particles incorporating carbon fibers, polyetheretherketone forming a matrix, and carbon fibers substantially incorporated into the matrix. The "average diameter D50" (the measurement method is not described in detail) is 20 μm to 150 μm. The average length of the carbon fibers is also 20 μm to 150 μm.

[0011] US Patent Application Publication No. 2005 / 0207931 describes three methods for preparing thermoplastic particles incorporating more than 30% by weight of carbon fibers (see Variant 3).

[0012] The first manufacturing method described is spray drying. This method consists of mixing fine thermoplastic resin powder of 3 μm to 10 μm by D50 with carbon fibers in a liquid phase such as ethanol or a water / ethanol mixture. The suspension is sprayed onto a surface and the liquid phase of the suspension is evaporated or deposited to form a powder.

[0013] The second method involves milling thermoplastic granules with an initial grain size of 3 mm, which already contain carbon fibers. Milling is carried out under cryogenic conditions in a mill equipped with pin discs until the particles reach the desired size and are then sorted by air separator.

[0014] The third manufacturing method is melt spraying, which consists in spraying a mixture of carbon fibers and molten thermoplastic resin to obtain particles with a size of the order of tens of micrometers.

[0015] These three methods can be very difficult to implement, especially when the thermoplastic resin is a polyaryletherketone, such as polyetheretherketone. While these methods can be reasonably implemented using polyaryletherketone as the thermoplastic resin, the resulting polyaryletherketone-filled powders have very high production costs. The first method, in particular, appears very difficult to implement due to its complexity and the high cost of obtaining polyaryletherketone particles with a size of several tens of micrometers used in the starting particles. The second method also appears complicated to implement due to the presence of carbon fibers in the milled granules, which tend to cause significant wear and accelerated mill aging. Furthermore, in the second method, the size of the carbon fibers incorporated into the polyaryletherketone particles is controlled by the particle size and generally does not exceed it. Finally, the third method is also complicated to implement because the correct production of the powder depends on the non-agglomeration of the sprayed particles, which is reflected in the need for an extremely fast and accurate cooling system.

[0016] As a result, powder compositions containing polyaryletherketone, forming matrices, and carbon fibers substantially embedded in the matrix have a much higher cost than dry blends of polyaryletherketone particles and carbon fibers. Additionally, the reinforcement obtained in three-dimensional objects by laser sintering compositions of PAEK particles incorporating carbon fibers is generally lower than that obtained by laser sintering dry blends of PAEK particles and carbon fibers. This is explained, particularly in the first case, by the fact that the size of the carbon fibers is largely controlled by the particle size. This is not the case in the second case, where the carbon fibers are much larger.

[0017] Therefore, there is a need to develop alternative filled polyaryletherketone powders to improve the mechanical properties, in particular to increase the modulus of elasticity and even the fracture stress of objects produced from these powders, especially those produced by electromagnetic radiation mediated sintering.

[0018] There is also a need to develop optimized methods for obtaining these packed powders. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] U.S. Patent Application Publication No. 2018 / 0201783 [Patent Document 2] U.S. Patent Application Publication No. 2005 / 0207931 Summary of the Invention [Problem to be solved by the invention]

[0020] The object of the present invention is therefore to propose a packed powder and a method for producing this powder that overcomes at least some of the drawbacks of the prior art.

[0021] One object of the present invention is to propose filled powders based on polyaryletherketones which result in objects with better mechanical properties, in particular higher moduli of elasticity and higher breaking stresses, than unfilled powders based on polyaryletherketones.

[0022] Another object of the invention is to propose a packed powder based on polyaryletherketone that results in objects whose mechanical properties are substantially isotropic.

[0023] According to a particular embodiment, one objective is to propose a filler powder that has a relatively low cost.

[0024] According to a particular embodiment, one objective is to propose a powder that results in objects with mechanical properties that are comparable or even better than those of powders based on polyaryletherketone containing carbon fibers (fibers or dry blends with incorporated fibers).

[0025] According to a particular embodiment, one objective is to propose a powder that can be used in an electromagnetic radiation mediated powder sintering process and, where appropriate, can be easily reused for one or more subsequent shapes.

[0026] A further object of the present invention is also to propose a method for producing the powder according to the invention, which is simple and has a relatively low cost. [Means for solving the problem]

[0027] The present invention relates to powders having a volume-weighted particle size distribution measured by laser diffraction according to standard ISO 13320:2009 with a median diameter D50 in the range of 40 to 120 micrometers.

[0028] the powder comprises at least one polyaryletherketone (PAEK) and at least one filler; - said at least one polyaryletherketone forms a matrix incorporating said at least one filler; - said fillers have an equivalent spherical diameter distribution, measured by X-ray by gravitational liquid sedimentation according to standard ISO 13317-3:2001, with a median diameter d'50 of less than or equal to 5 micrometers.

[0029] The term "D50" means the powder particle size value at which the cumulative volume-weighted particle size distribution function is equal to 50%. "D50" is measured by laser diffraction, for example using a Malvern Mastersizer 2000® diffractometer, in accordance with standard ISO 13320:2009.

[0030] The term "D'50" refers to the filler particle size value at which the cumulative volume-weighted particle size distribution function is equal to 50%. "D'50" is measured by laser diffraction, for example using a Malvern Mastersizer 2000® diffractometer, in accordance with standard ISO 13320:2009.

[0031] The term "d'50" refers to the filler particle size value at which the cumulative Stokes equivalent sphere diameter distribution function is equal to 50%. "d'50" is measured by gravity sedimentation in liquid according to standard ISO 13317-3:2001, for example using a Sedigraph III Plus® machine.

[0032] Standard ISO 9276 is used for mathematical and statistical modeling to calculate particle size distributions.

[0033] For filler particles of substantially spherical shape, D'50 and d'50 are substantially equal. For filler particles of non-spherical shape, particularly for particles of flat and / or elongated shape that can be described by a characteristic length and a characteristic thickness, the shape factor C is determined by the following formula:

[0034]

number

[0035] is defined by

[0036] The term "Z-axis" refers to the direction in which the various layers are printed in the layer-by-layer electromagnetic radiation-mediated powder sintering process, whereas the term "XY" refers to the plane in which each layer is printed.

[0037] The inventors of the present invention have surprisingly found that the claimed powders make it possible to produce three-dimensional objects, via layer-by-layer fabrication of the objects by an electromagnetic radiation-mediated sintering process, having mechanical properties superior to those of objects produced from unfilled powders based on polyaryletherketone. In particular, powders incorporating a filler comprising a PAEK and having a d'50 substantially smaller than the D50 of the powder make it possible, in particular, to obtain three-dimensional objects with higher stiffness and / or higher fracture strength by laser sintering.

[0038] The inventors have also been able to demonstrate that in certain embodiments, the powders according to the invention allow for the production of three-dimensional objects, via a process of layer-by-layer fabrication of objects by electromagnetic radiation mediated sintering, with mechanical properties (in particular breaking strength and elongation at break) that are of the same order of magnitude or even exceed those of objects obtained from powders based on polyaryletherketone and carbon fibers (dry blend of fibers or incorporation of fibers in a matrix).

[0039] In addition, the mechanical properties of three-dimensional objects produced from the powders according to the invention are isotropic or quasi-isotropic, i.e. equivalent in all spatial directions.

[0040] According to certain embodiments, the filler has a particle size distribution with a median diameter d'50 of less than or equal to 2.5 micrometers.

[0041] According to a particular embodiment of the invention, the weight ratio of filler to said at least one PAEK is between 1:9 and 1:1.

[0042] For mass ratios less than 1:9, the gains in mechanical properties, particularly the increase in modulus values, of objects made from powders are generally not substantial relative to objects made from unfilled powders. For mass ratios greater than 1:1, objects made from powders are generally too brittle.

[0043] Preferentially, the weight ratio of filler to said at least one PAEK is between 1:4 and 3:7.

[0044] In certain embodiments, the at least one PAEK and the at least one filler together represent at least 60%, or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 92.5%, or at least 95%, or at least 97.5%, or at least 98%, or at least 98.5%, or at least 99%, or at least 99.5%, or 100% of the total weight of the powder.

[0045] In a particular embodiment, the PAEK is a statistical copolymer of polyetherketoneketone (PEKK) consisting essentially of, and preferentially consisting of, terephthalic acid units and isophthalic acid units, The formula for the terephthalic acid unit (T) is:

[0046] [ka]

[0047] and The formula of the isophthalic acid unit (I) is:

[0048] [ka]

[0049] is.

[0050] In a particular embodiment, the mass percentage of terephthalic acid units relative to the sum of terephthalic acid units and isophthalic acid units is 55% to 65%. Preferentially, the mass percentage of terephthalic acid units relative to the sum of terephthalic acid units and isophthalic acid units is about 60%.

[0051] In certain embodiments, the at least one PAEK is - units of the formula: -Ph-O-Ph-O-Ph-C(O)-, and - units of the formula: -Ph-O-Ph-Ph-O-Ph-C(O)-, wherein Ph represents a phenylene group, -C(O)- represents a carbonyl group, and each phenylene is independently in the ortho, meta or para configuration, preferentially in the meta or para configuration. and preferentially a copolymer consisting essentially of these.

[0052] According to a particular embodiment, the filler is a mineral filler. The filler may be preferentially selected from the group consisting of calcium carbonate, silica, talc, wollastonite, mica, kaolin, and mixtures thereof. More preferably, the filler is talc. Talc has the advantage of low cost and being able to advantageously enhance the properties of the objects obtained from the powder according to the invention.

[0053] According to certain embodiments, the filler has a shape factor C of 2 or greater, said shape factor C being defined by the following formula:

[0054]

number

[0055] where D'50 represents the volume-weighted median diameter of the filler particles, measured according to standard ISO 13320:2009; where d'50 represents the median Stokes equivalent sphere diameter of the filler particles, measured by X-ray by gravitational liquid sedimentation according to standard ISO 13317-3:2001] is defined by

[0056] The present invention further provides a method for producing a powder, comprising the steps of: - providing at least one polyaryletherketone (PAEK) and providing at least one filler; the at least one filler has a Stokes sphere equivalent size distribution measured by X-ray by gravity liquid sedimentation according to standard ISO 13317-3:2001 with a median size d'50 of 5 micrometers or less; - extrusion granulation of said at least one polyaryletherketone (PAEK) together with said at least one filler to form granules; - milling the granules to obtain a powder having a volume-weighted particle size distribution, measured by laser diffraction according to standard ISO 13320:2009, with a median diameter D50 in the range of 40 to 120 micrometers; The present invention relates to a method comprising the steps of:

[0057] The inventors of the present invention have surprisingly found that milling of PAEK-based granules incorporating fillers with a d'50 of 5 micrometers or less is facilitated compared to PAEK-based granules incorporating carbon fibers. The selection of a filler with a d'50 of 5 micrometers or less makes it possible to easily obtain powders with a D50 in the range of 40 to 120 micrometers. Milling times are therefore shorter. In addition, PAEK-based granules incorporating fillers with a d'50 of 5 micrometers or less are generally much less abrasive during milling than prior art PAEK-based granules incorporating carbon fibers. Therefore, the mill is not subjected to excessive wear.

[0058] In certain embodiments, the method also includes the step of heat treating the granules prior to the milling step to allow at least partial crystallization of said at least PAEK in the powder.

[0059] The present invention further relates to a method for layer-by-layer fabrication of objects by electromagnetic radiation-mediated sintering, which method uses a powder according to the invention. In other words, the present invention further relates to the use of the powder as described above in a method for layer-by-layer fabrication of objects by sintering mediated by at least one electromagnetic radiation.

[0060] Finally, the invention relates to any object obtainable via a method for layer-by-layer fabrication of objects by electromagnetic radiation-mediated sintering, characterized in that it has a tensile modulus of 7 GPa or more in at least one direction, according to standard ISO 527-2:2012, at a traverse speed of 1 mm / min at 23° C. on a 1BA type specimen, since the mechanical properties of the object are quasi-isotropic, and therefore have a tensile modulus of 7 GPa or more in all spatial directions, in particular in the XY plane and along the Z axis. [Brief explanation of the drawings]

[0061] [Figure 1] FIG. 1 shows a device for carrying out a method for layer-by-layer fabrication of three-dimensional objects by a sintering process in which the powder according to the invention can be used. DETAILED DESCRIPTION OF THE INVENTION

[0062] Polyaryletherketone The powder polyaryletherketone (PAEK) according to the invention has the following formula: (-Ar-X-) and (-Ar1-Y-) [In the formula, Ar and Ar1 each represent a divalent aromatic group, and Ar and Ar1 may preferably be selected from 1,3-phenylene, 1,4-phenylene, 4,4'-biphenylene, 1,4-naphthylene, 1,5-naphthylene and 2,6-naphthylene; X represents an electron-withdrawing group, which may preferably be chosen from a carbonyl group and a sulfonyl group, - Y represents an oxygen atom, a sulfur atom, or an alkylene group, for example a group selected from -(CH)2- and isopropylidene. Includes units having the formula:

[0063] In these units X and Y, at least 50%, preferably at least 70%, more particularly 80% of the X groups are carbonyl groups and at least 50%, preferably at least 70%, more particularly at least 80% of the Y groups are oxygen atoms.

[0064] According to a preferred embodiment of the invention, 100% of the X groups represent carbonyl groups and 100% of the Y groups represent oxygen atoms.

[0065] Advantageously, the powdered PAEK is - polyetherketoneketone, also known as PEKK, containing one or more units of the formula: -Ph-O-Ph-C(O)-Ph-C(O)-; - polyetheretherketone, also known as PEEK, containing one or more units of the formula: -Ph-O-Ph-O-Ph-C(O)-; - polyetherketone, also known as PEK, containing one or more units of the formula: -Ph-O-Ph-C(O)-; - polyetheretherketoneketone, also known as PEEKK, containing one or more units of the formula: -Ph-O-Ph-O-Ph-C(O)-Ph-C(O)-; - polyetheretheretherketone, also known as PEEEK, containing one or more units of the formula: -Ph-O-Ph-O-Ph-O-Ph-C(O)-; - polyether diphenyl ether ketone, also known as PEDEK, containing one or more units of the formula: -Ph-O-Ph-Ph-O-Ph-C(O)-; - mixtures thereof; and - these copolymers may be selected from:

[0066] In the formulae listed above, Ph represents a phenylene group, -C(O)- represents a carbonyl group, and each phenylene is optionally and independently in ortho (1-2), meta (1-3) or para (1-4) form, preferentially in meta or para form.

[0067] Additionally, defects, end groups and / or monomers may be incorporated into the polymers listed above in small amounts without affecting the performance of those polymers (incidence).

[0068] In certain embodiments, the at least one PAEK is a PEKK, which has the formula:

[0069] [ka]

[0070] "Type I" ("isophthalic type") units and formula:

[0071] [ka]

[0072] "T-type" ("terephthalic type") units It may be a copolymer consisting essentially of, or preferentially consisting of, these.

[0073] The mass ratio of T units to the sum of T and I units in PEKK can be in the range of 0% to 5%, or 5% to 10%, or 10% to 15%, or 15% to 20%, or 15% to 20%, or 20% to 25%, or 25% to 30%, or 30% to 35%, or 35% to 40%, or 40% to 45%, or 45% to 50%, or 50% to 55%, or 55% to 60%, or 60% to 65%, or 65% to 70%, or 70% to 75%, or 75% to 80%, or 80% to 85%, or 85% to 90%, or 90% to 95%, or 95% to 100%. The selection of the mass ratio of T units to the sum of T and I units is one of the factors that allows for the adjustment of the melting point and crystallization rate of PEKK at a given temperature. A given mass ratio of T units to the sum of T and I units can be obtained by adjusting the individual concentrations of the reagents during polymerization in a manner known per se.

[0074] According to an advantageous embodiment, the sum of terephthalic acid units and isophthalic acid units in the PEKK is between 55% and 65%, and preferentially the mass percentage of terephthalic acid units relative to the sum of terephthalic acid units and isophthalic acid units is about 60%.

[0075] In certain embodiments, the at least one PAEK is a PEEK-PEDEK copolymer having the formula:

[0076] [ka]

[0077] Units and formula:

[0078] [ka]

[0079] It can consist essentially of, and preferentially consist of, units of

[0080] The molar ratio of units (III) to the sum of units (III) and units (IV) of PEEK-PEDEK may be in the range of 0% to 5%, or 5% to 10%, or 10% to 15%, or 15% to 20%, or 20% to 25%, or 25% to 30%, or 30% to 35%, or 35% to 40%, or 40% to 45%, or 45% to 50%, or 50% to 55%, or 55% to 60%, or 60% to 65%, or 65% to 70%, or 70% to 75%, or 75% to 80%, or 80% to 85%, or 85% to 90%, or 90% to 95%, or 95% to 100%. The choice of the molar ratio of units (III) to the sum of units (III) and units (IV) is one of the factors that allows the melting point and crystallinity of the PEEK-PEDEK copolymer to be adjusted at a given temperature. The molar ratio of units (III) to the sum of units (III) and units (IV) can be obtained by adjusting the individual concentrations of the reagents during the polymerization in a manner known per se.

[0081] The viscosity index of the PAEK, measured as a solution at 25°C in 96% by weight aqueous sulfuric acid according to standard ISO 307:2019, is between 0.65 dl / g and 1.15 dl / g, preferentially between 0.70 dl / g and 1.05 dl / g and more preferably between 0.70 dl / g and 0.92 dl / g.

[0082] Filler At least one filler in the powder according to the invention has a Stokes sphere equivalent size distribution measured by X-ray by gravitational liquid sedimentation according to standard ISO 13317-3:2001 with a median size d'50 of less than or equal to 5 micrometers.

[0083] The filler may in particular have a particle size distribution with a median diameter d'50 of 2.5 micrometers or less. In certain cases, the filler may have a particle size distribution with a median diameter d'50 of 2 micrometers or less, or 1.5 micrometers or less, or 1 micrometer or less. The median diameter d'50 of the filler is generally 0.1 micrometers or more.

[0084] In certain embodiments, the median diameter d'50 is 0.1 to 5.0 micrometers, or 0.25 to 4.0 micrometers, or 0.5 to 3.0 micrometers. The median diameter d'50 may be, in particular, 0.1 to 0.5 micrometers, or 0.5 to 1.0 micrometers, or 1.0 to 1.5 micrometers, or 1.5 to 2.0 micrometers, or 2.0 to 2.5 micrometers, or 2.5 to 3.0 micrometers, or 3.0 to 3.5 micrometers, or 3.5 to 4.0 micrometers, or 4.0 to 4.5 micrometers, or 4.5 to 5.0 micrometers.

[0085] Advantageously, the filler is a mineral filler.

[0086] Advantageously, the filler is a reinforcing filler, ie a filler that is capable of increasing the hardness, in particular the tensile modulus and / or the strength at break, of said at least one polyaryletherketone (PAEK).

[0087] The filler may include calcium carbonate (calcite).

[0088] The filler may also comprise silica. The filler may in particular be pure silica (SiO2), synthetic silica, quartz or diatomaceous flour.

[0089] Fillers may also include talc.

[0090] The filler may also include wollastonite.

[0091] Finally, the filler may comprise clay or aluminosilicate, and may in particular be kaolin, natural slate flour, vermiculite or mica.

[0092] The filler is advantageously talc, which has the advantage that it has a low cost and can advantageously enhance the properties of the objects obtained from the powder according to the invention.

[0093] The filler is advantageously non-spherical. It is characterized by a shape factor C, which is advantageously greater than or equal to 2. The shape factor C is generally less than or equal to 20.

[0094] Powder manufacturing method In the process for producing the powder according to the present invention, the polyaryletherketone and filler are blended and then extruded.

[0095] In a first embodiment, at least one filler and at least one polyaryletherketone are dry blended and charged into the main hopper of the extruder.

[0096] According to a second, more advantageous embodiment, the at least one polyaryletherketone is introduced into the main hopper, while the at least one filler is introduced by side feeding and added to the molten polyaryletherketone, which has the advantage of preventing the filler from being excessively damaged during passage through the extruder.

[0097] Any extruder suitable for extruding high-melting polymers may be used. Those skilled in the art can further adapt the extrusion conditions as a function of the polymer used. An example of an extruder is a "Labtech" twin-screw extruder with a screw diameter of 26 mm and an L / D ratio of 40.

[0098] The extruded mixture is subdivided to form granules.

[0099] The granules are then optionally heat treated to increase the crystallinity of the polyaryletherketone, since a high crystallinity of the granules makes it possible to facilitate the following milling step. Advantageously, the PAEK fraction in the powder has a heat of fusion ranging from 20 to 50 J / g (PAEK), preferentially from 25 to 40 J / g (PAEK), measured during the first heating according to standard ISO 11357-2:2013 using a heating rate of 20°C / min.

[0100] The heat treatment is advantageously carried out at a temperature much lower than the melting point of the powder. According to variants in which the powder is a PEKK-based powder with a mass percentage of terephthalic acid units relative to the sum of terephthalic acid units and isophthalic acid units of 55% to 65%, the heat treatment can be carried out at a temperature of 180°C to 220°C.

[0101] The granules are then milled to a powder so as to obtain a powder with a particle size distribution having a median diameter D50 in the range of 40 to 120 micrometers. The granules according to the invention are more brittle than PAEK granules incorporating carbon fibers (at the same volume content of filler), which facilitates the milling process. In addition, PAEK granules incorporating a filler, advantageously talc, having a d'50 of 5 micrometers or less are generally much less abrasive during milling than PAEK granules incorporating carbon fibers.

[0102] Milling may be carried out at temperatures below -20°C, preferentially below -40°C, by cooling with liquid nitrogen, liquid carbon dioxide, or cardice, or liquid helium. The mill used is advantageously a pin mill, in particular a counter-rotating pin mill, or alternatively an impact mill, such as a hammer mill, or alternatively a vortex mill. The mill may be equipped with a sieve through which the milled particles are passed and through which particles of the desired size pass. The particles retained by the sieve can be conveyed back into the mill and subjected to longer milling.

[0103] powder The mass ratio of the at least one filler to the at least one PAEK may be 1:9 to 1:1. For mass ratios less than 1:9, the gain in mechanical properties of objects made from the powder, especially the increase in modulus values, is generally not substantial compared to objects made from unfilled PAEK powder. For mass ratios greater than 1:1, the objects made from the powder are generally too brittle. The mass ratio of the at least one filler to the at least one PAEK may advantageously be 1:4 to 3:7.

[0104] The weight ratio of the at least one filler to the at least one PAEK may also be from 3:7 to 2:3, or from 2:3 to 1:1.

[0105] The PAEK and filler together represent at least 60%, or at least 70%, or at least 80%, or at least 85%, or at least 90%, or at least 92.5%, or at least 95%, or at least 97.5%, or at least 98%, or at least 98.5%, or at least 99%, or at least 99.5%, or 100% of the total weight of the powder.

[0106] In addition to the PAEK and filler, the powder may contain other polymers not belonging to the PAEK family, in particular other thermoplastic polymers.

[0107] The powder may also contain additives, such as flow agents, stabilizers (light, especially UV, and heat stabilizers), optical brighteners, dyes, pigments, and energy absorbing additives (including UV absorbers). The additives generally constitute less than 5% by weight of the total powder mass, and preferably less than 1% by weight of the total powder mass.

[0108] Use of powder Powders according to the present invention may be used in a number of applications, including the non-exhaustive list below.

[0109] The powders according to the invention can be used in a method for electromagnetic radiation mediated layer-by-layer sintering shaping of objects. The infrared laser and laser radiation sintering process is shown in Figure 1 and has already been described in the section dealing with the prior art.

[0110] The powder according to the invention can also be used in processes for painting metal surfaces. To finally obtain a coating on the metal part, various processes can be used. An example is fluidized bed immersion, where the metal part is heated and then immersed in a fluidized powder bed. It is also possible to carry out electrostatic powder coating (where an electrically charged powder is dispersed onto a grounded metal part). In this case, a thermal post-treatment is carried out to produce the coating. An alternative method is to carry out powder coating on a preheated part. This makes it possible to eliminate the heat treatment after powder coating. Finally, it is possible to carry out flame powder coating. In this case, the powder is molten and sprayed onto an optionally preheated metal part.

[0111] The powders according to the present invention can also be used in powder compaction processes. These processes are generally used to produce thick parts. In these processes, the powder is first loaded into a mold, compacted, and then melted to produce the part. Finally, a suitable cooling (usually a relatively slow cooling) is carried out to remove internal stresses within the part.

[0112] Experimental data The powders in the following examples were produced by compounding (extrusion granulation) of various compositions, heat treating and then milling.

[0113] The compounding was carried out in a "Labtech" twin-screw extruder with a screw diameter of 26 mm and an L / D ratio of 40, a flat temperature profile of 350° C. and a screw speed of 400 rpm. Granules with a length equal to about 2 mm were obtained.

[0114] When producing filled powders (carbon fiber or talc), the filler is introduced into the compounding by side feeding. The resulting granules are called "filled."

[0115] The granules were then heat treated at 180°C for 9 hours.

[0116] Finally, the heat-treated granules were milled in a liquid nitrogen cooled Mikropull 2DH® cryogenic hammer mill, which was further equipped with a grate with 500 μm round holes. [Example]

[0117] Example 1 (Comparative Example) The first composition used is a polyetherketoneketone having a viscosity index of 0.75 dl / g at 25°C in a 96% by weight aqueous sulfuric acid solution, according to standard ISO 307:2019 applicable to PAEKs, and a mass ratio of T units to the sum of T and I units of 60%. This polyetherketoneketone is sold under the trade name Kepstan® by the company Arkema.

[0118] The granules obtained with the composition according to Example 1 could be milled to obtain a D50 of 500 microns, measured using a Malvern Mastersizer 2000® diffractometer.

[0119] Example 2 (Comparative Example) The second composition used consisted of polyetherketoneketone according to Example 1 and carbon fibres, the carbon fibres making up 23% by weight of the composition.

[0120] The carbon fibers used were Tenax®-A fibers of the "HT M100" type, ie fibers with a fiber length between 60 micrometers and 100 micrometers.

[0121] The granules obtained with the composition according to Example 2 could be milled to obtain a D50 of 160 microns, measured using a Malvern Mastersizer 2000® diffractometer.

[0122] Example 3 (inventive example) The third composition used consisted of polyetherketoneketone according to Example 1 and Jetfine® 0.7C talc sold by the company Imerys, the talc making up 30% by weight of the composition (so as to ensure a volume proportion of filler corresponding to that of Example 2).

[0123] Jetfine® 0.7C talc has a d'50 of 0.7 microns measured with a Sedigraph III Plus® machine and a D'50 of 2.5 microns measured with a Malvern Mastersizer 2000® diffractometer, i.e. a shape factor C equal to 2.6.

[0124] The granules obtained with the composition according to Example 3 could be milled to obtain a D50 of 120 microns, measured using a Malvern Mastersizer 2000® diffractometer.

[0125] Example 4 (inventive example) The third composition used consisted of polyetherketoneketone according to Example 1 and Steaplus® HAR T77 talc sold by the company Imerys, the talc making up 30% by weight of the composition (so as to ensure a volume proportion of filler corresponding to that of Example 2).

[0126] Steaplus® HAR T77 talc has a d'50 of 2.2 microns measured with a Sedigraph III Plus® machine and a D'50 of 10.5 microns measured with a Malvern Mastersizer 2000® diffractometer, i.e. a shape factor C equal to 3.8.

[0127] The granules obtained with the composition according to Example 4 could be milled to obtain a D50 of 110 microns, measured using a Malvern Mastersizer 2000® diffractometer.

[0128] The results of milling the powders according to Examples 3 and 4 (examples according to the invention) compared to the results of milling the powders according to Examples 1 and 2 (comparative examples) show that milling of PEKK granules incorporating a talc filler with a d'50 of 5 micrometers or less is facilitated compared to unfilled PEKK granules or PEKK granules incorporating carbon fibres with the same volume content as the filler.

[0129] Example 6 (Comparative Example) Specimens of type 1BA according to standard ISO 527-2:2012 were produced by laser sintering of 6002PL powder sold by Arkema in an EOS P800 printer sold by EOS. The powder has a D50 equal to 50 μm, measured using a Malvern Mastersizer 2000 diffractometer, and a viscosity index of 0.96 dl / g at 25° C. in a 96% by weight aqueous sulfuric acid solution according to standard ISO 307:2019 applicable to PAEKs. Specimens of type 1BA were produced by laser sintering of 28 mJ / mm at a build temperature of 290° C. 2 The laser sintering energy was used to create shapes along the X, Y, and Z axes.

[0130] Regardless of the build axis of the sample in the laser sintering machine, a tensile modulus of 4 GPa was measured at 23°C using an MTS810® machine equipped with a mechanical extensometer sold by MTS Systems Corporation at a travel speed of 1 mm / min according to standard ISO 527-2:2012.

[0131] Example 7 (inventive example) Specimens of type 1BA according to standard ISO 527-2:2012 were produced by injecting the powder according to Example 3 with a feed temperature of 320°C, a screw outlet temperature of 340°C, a mold temperature of 80°C and a cycle time of less than 1 minute.

[0132] A tensile modulus of 9 GPa was measured at 23° C. at a displacement speed of 1 mm / min according to standard ISO 527-2:2012 using an MTS810® machine equipped with a mechanical extensometer sold by MTS Systems Corporation.

[0133] It is believed that the modulus values obtained for samples produced by injection molding are equal to or less than the values that can be determined for samples produced by laser sintering. Thus, if a sample were produced by laser sintering, it would necessarily have a tensile modulus of at least 9 GPa.

[0134] Example 8 (in accordance with the invention) Specimens of type 1BA according to standard ISO 527-2:2012 were produced by injection molding of the powder according to example 4, following the same protocol as that of example 7.

[0135] Following the same protocol as in Example 7, the 9 GPa tensile modulus was also measured.

[0136] Similarly, if the sample was fabricated by laser sintering, it would necessarily have a tensile modulus of at least 9 GPa.

[0137] The results of the mechanical tests according to Examples 7 and 8 (examples according to the invention) compared to the results of the mechanical tests according to Example 6 (comparative example) show that the mechanical properties of objects obtained from PEKK powder incorporating a talc filler having a d'50 of 5 micrometers or less are higher than those obtained from unfilled PEKK powder.

[0138] The mechanical testing results of Examples 7 and 8 further demonstrate that the mechanical properties of objects obtained from PEKK powders incorporating talc fillers with a d'50 of 5 micrometers or less are comparable to or even exceed those of objects obtained from powders filled with carbon fiber, when compared at the same volumetric filler content. Specifically, the specifications for the material HT-23® sold by Advanced Laser Materials indicate tensile moduli of 6.5 GPa along X, 6.4 GPa along Y, and 5.8 GPa along Z. These values were measured according to ASTM D638. HT-23® is a polyetherketoneketone powder incorporating 23% carbon fiber and intended for laser sintering applications in printers such as the EOS P500® and EOS P810® machines sold by EOS. [Explanation of symbols]

[0139] 1. Laser sintering device 10 Sintering chamber 20 Laser 30 horizontal board 40 Supply Tank 50 powder bed 55 Sintered parts 56 Unsintered Powder 80 Three-dimensional objects 100 Infrared 200 Laser Radiation

Claims

1. A powder having a volume-weighted particle size distribution, measured by laser diffraction according to standard ISO 13320:2009, with a median diameter D50 in the range of 40 to 120 micrometers, comprising at least one polyaryletherketone (PAEK) and at least one filler; - said at least one polyaryletherketone forms, at least in part, a matrix incorporating said at least one filler; - the filler has a Stokes sphere equivalent size distribution, measured by X-ray by gravitational liquid sedimentation according to standard ISO 13317-3:2001, with a median size d'50 of 5 micrometers or less, and A powder wherein the filler is talc.

2. 2. The powder of claim 1, wherein the filler has a Stokes sphere equivalent diameter distribution with a median diameter d'50 of 2.5 micrometers or less.

3. 3. The powder according to claim 1, wherein the mass ratio of the filler to the at least one PAEK is from 1:9 to 1:

1.

4. 4. The powder of claim 3, wherein the mass ratio of the filler to the at least one PAEK is from 1:4 to 3:

7.

5. 5. Powder according to any one of claims 1 to 4, wherein the at least one PAEK and the at least one filler together represent at least 60% of the total weight of the powder.

6. the at least one PAEK is a statistical copolymer of polyetherketoneketone (PEKK) consisting essentially of terephthalic acid units and isophthalic acid units; The formula of the terephthalic acid unit (T) is: 【Chemical 1】 and The formula of the isophthalic acid unit (I) is: 【Chemistry 2】 That is, The powder according to any one of claims 1 to 5.

7. The powder according to claim 6, wherein the mass percentage of the terephthalic acid units relative to the total mass of the terephthalic acid units and the isophthalic acid units is 55% to 65%.

8. the at least one PAEK - units of the formula: -Ph-O-Ph-O-Ph-C(O)-, and - units of the formula: -Ph-O-Ph-Ph-O-Ph-C(O)-, wherein Ph represents a phenylene group, -C(O)- represents a carbonyl group, and each phenylene may independently be in the meta or para configuration.

6. The powder according to claim 1, which is a copolymer consisting of

9. The filler has a shape factor C of 2 or greater, and the shape factor C satisfies the following formula: [Equation 1] [In the formula, D'50 represents the volume-weighted median diameter of the filler particles, measured according to standard ISO 13320:2009, d'50 represents the median Stokes equivalent spherical diameter of the filler particles, measured by X-ray by gravitational liquid sedimentation according to standard ISO 13317-3:2001] 9. The powder of claim 1 , wherein:

10. A manufacturing method for producing the powder according to any one of claims 1 to 9, comprising: - providing at least one polyaryletherketone (PAEK) and providing at least one filler; the at least one filler has a Stokes sphere equivalent size distribution measured by X-ray by gravity liquid sedimentation according to standard ISO 13317-3:2001 with a median size d'50 of 5 micrometers or less; - extrusion granulation of said at least one polyaryletherketone (PAEK) together with said at least one filler to form granules; - milling the granules to obtain a powder with a particle size distribution measured by laser diffraction according to standard ISO 13320:2009, with a median diameter D50 in the range of 40 to 120 micrometers. A manufacturing method comprising the steps of:

11. - heat treating the granules before the milling step to allow at least partial crystallization of said at least one PAEK. The method of claim 10 further comprising:

12. 10. A method for layer-by-layer fabrication of objects by electromagnetic radiation mediated sintering, using a powder according to any one of claims 1 to 9.

13. 13. A method for layer-by-layer fabrication of an object according to claim 12, characterized in that the object has a tensile modulus of 7 GPa or more in at least one direction according to standard ISO 527-2:2012 at a translation speed of 1 mm / min at 23°C on a 1BA type specimen.

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