Thermoplastic powder composition and reinforced three-dimensional object produced by 3D printing of such a composition

Abstract

The present invention relates to a reinforced thermoplastic powder composition, comprising: at least one polyamide powder with a d50 of less than 100 μm, from 5% to 70% by weight of at least one glass fiber: with a l50 within the range from 50 to 200 μm, with an lmax of less than 450 μm, with a d50 within the range from 4 to 40 μm, with a form factor F: l50/d50 of between 5 and 15, and from 0.05% to 5% of a pulverulent flow agent with a d50 of less than 20 μm; with regard to the total weight of the composition. The present invention relates in particular to the use of said composition in 3D printing processes for manufacturing reinforced three-dimensional objects.

Claims

1. A reinforced thermoplastic powder composition, comprising: at least one polyamide powder with a d50 of less than 100 μm, from 5% to 70% by weight of glass fibers: with an l50 within the range from 50 to 200 μm, with an lmax of less than 450 μm, with a d50 within the range from 4 to 40 μm, with a form factor F: l50/d50 of between 5 and 15, and from 0.05% to 5% of a pulverulent flow agent with a d50 of less than 20 μm; with regard to the total weight of the composition, wherein the pulverulent flow agent is chosen from: silicas, hydrated silicas, amorphous alumina, vitreous silicas, vitreous phosphates, vitreous borates, vitreous oxides, titanium dioxide, talc, mica, fumed silicas, pyrogenic silicas, kaolin, attapulgite, calcium silicates, alumina and magnesium silicates.

2. The composition as claimed in claim 1, in which said polyamide is chosen from: polyamides and copolyamides comprising at least one of the following monomers: 46, 4T, 54, 59, 510, 512, 513, 514, 516, 518, 536, 6, 64, 69, 610, 612, 613, 614, 616, 618, 636, 6T, 9, 104, 109, 1010, 1012, 1013, 1014, 1016, 1018, 1036, 10T, 11, 12, 124, 129, 1210, 1212, 1213, 1214, 1216, 1218, 1236, 12T, MXD6, MXD10, MXD12, and MXD14.

3. The composition as claimed in claim 1, in which said polyamide is chosen from: PA 11, PA 12, PA 1010, PA 6, PA 6/12, PA 11/1010, and their mixtures.

4. The composition as claimed in claim 1, in which the glass fibers comprise, expressed in terms of oxides as % by weight with regard to the weight of glass fiber: from 52% to 74% of silicon dioxide (SiO.sub.2), from 2% to 26% of aluminum oxide (Al.sub.2O.sub.3), from 0% to 23% of boron oxide (B.sub.2O.sub.3), from 0% to 25% of calcium oxide (CaO), from 0% to 25% of magnesium oxide (MgO), from 0% to 5% of zinc oxide (ZnO), from 0% to 5% of strontium oxide (SrO), from 0% to 1% of barium oxide (BaO), from 0% to 5% of lithium oxide (Li.sub.2O), from 0% to 16% of sodium oxide (Na.sub.2O), from 0% to 20% of zirconium oxide (ZrO.sub.2), from 0% to 3% of potassium oxide (K.sub.2O), from 0% to 3% of titanium oxide (TiO.sub.2), from 0% to 3% of iron oxide (Fe.sub.2O.sub.3).

5. The composition as claimed in claim 1, in which the glass fibers represent from 5% to 60% by weight, with regard to the total weight of the composition.

6. The composition as claimed in claim 1, in which the glass fibers exhibit: an l50 within the range from 100 to 200 μm, a d50 within the range from 6 to 30 μm, a form factor F: l50/d50 of between 8 and 12.

7. The composition as claimed in claim 1, in which the d50 of the glass fibers is within the range from 10 to 25 μm.

8. The composition as claimed in claim 1, in which the form factor F: l50/d50 of the fibers is within the range from 9 to 11.

9. A process for the manufacture of a powder composition as claimed in claim 1, comprising the following stages: a) mixing by dry blending of the polyamide powder with the glass fibers; b) adding the flow agent to the powder obtained in a).

10. A process for the manufacture of a reinforced three-dimensional object, comprising layer-by-layer sintering of a powder having a composition in accordance with claim 1, said process producing an X/Y construction.

11. A reinforced three-dimensional object manufactured according to the process of claim 10, said object having mechanical properties which are superior to those of an object of the same shape manufactured by an injection molding process of said composition.

12. The object as claimed in claim 11, wherein the object exhibits: an elastic modulus of at least 3000 MPa, an elongation at break of greater than 6%, a breaking stress of greater than 60 MPa, and a heat deflection temperature (HDT) of at least 150° C.

13. The object as claimed in claim 11, said object being a component of sports equipment, of a shoe, of a sports shoe, of a shoe sole, of a decoration, of luggage, of glasses, of furniture, of audio-visual equipment, of a computer or of automobile or aeronautical equipment and/or a component of medical equipment.

14. A process for manufacturing an object, comprising 3D-printing the object using 25% to 40% by weight of glass fibers: with a l50 within the range from 50 to 200 μm, with an lmax of less than 450 μm, with a d50 within the range from 4 to 40 μm, with a form factor F: l50/d50 of between 5 and 15, in a polyamide-based powder with a d50 of less than 100 μm, wherein the object has a modulus greater than the modulus of an object of the same shape manufactured by injection molding of the same composition.

15. The process as claimed in claim 14, in which the glass fibers exhibit: an l50 within the range from 100 to 200 μm, a d50 within the range from 10 to 25 μm, a form factor F: l50/d50 of between 8 and 12.

Description

EXAMPLES

(1) The examples below illustrate the present invention without limiting the scope thereof. In the examples, unless otherwise indicated, all the percentages and parts are expressed by weight.

(2) Products used in the compositions of the following tests (examples and comparatives):

(3) PA11-Based Powder:

(4) PA 11 powder synthesized by grinding a prepolymer obtained by polycondensation of 11-aminoundecanoic acid, followed by treatment with water and rise in viscosity. The PA 11 powder has a relative viscosity equal to 1.20 (20° C., in 0.5% by weight solution in meta-cresol).

(5) Although the tests refer to a composition based on Rilsan® PA11, it is understood that the compositions according to the present invention are not limited to this embodiment but can comprise any type of polyamide, alone or as a mixture.

(6) The Flow Agent:

(7) The flow agent used in all the following tests is fumed silica, it represents less than 0.5% by weight and its content is the same in each composition. Its d50 is less than 20 μm.

(8) Glass Fibers:

(9) The glass fibers are of E type (DIN 1259).

(10) The compositions of tests 1) to 3) use 25% of glass fibers, the size and shape characteristics of which are shown in table 3 below: 1) Example 1 (Ex1) 2) Comparative example 2 (Cp2) 3) Comparative example 3 (Cp3)

(11) The compositions of tests 4) and 5) use 30% of glass fibers: 4) Comparative example 4 (Cp4) 5) Example 5 (Ex5)

(12) TABLE-US-00003 TABLE 3 1) 2) 3) 4) 5) Ex1 Cp2 Cp3 Cp4 Ex5 mean fiber d50 14 μm 14 μm 14 μm 16 μm 14 μm diameter mean fiber l50 150 μm 210 μm 50 μm Presence of 150 μm length long fibers >500 μm fiber sizing silane silane silane silane silane treatment form factor F = 10.7 15 3.6 10 10.7 l50/d50 addition of by: dry blend mixing 25% GF in the PA11- dry blend mixing 30% the fibers based powder GF in the PA11-based powder flowability Ø 25 mm 4 s 40 s 4.8 s 12 s 5.7 s Ø 15 mm 16 s difficult (>50 impossible impossible 23.3 s s − 1 min) Ø 10 mm difficult impossible impossible impossible impossible (>1 min 20) 3D printing X/Y construction X/Y construction passage through the OK difficult impossible difficult OK machine elastic (Objective > 3800 MPa 4200 MPa — 2930 MPa 3880 MPa modulus 3000 MPa) elongation at (objective > 9-10% 6% — 15% 7.30% break 6%) HDT (objective > 185-187° C. <150° C. — <150° C. >150° C. 150° C.) breaking (objective > 61-62 MPa 70 MPa — 48.4 MPa 65.8 MPa stress 60 MPa)

(13) Passage of the Compositions Obtained Through the Machine for Sintering:

(14) A Laser Sintering Formiga P100 (EOS) machine is used.

(15) The conditions for passage through the laser machine which are fixed and common to all the compositions are: outline speed=1500 mm/s, hatch speed=2500 mm/s, “beam offset” hatching=0.15 mm

(16) The conditions of the tests of table 3 shown in the following table 4:

(17) TABLE-US-00004 TABLE 4 Exposure Shrinkage Laser power Laser power chamber chamber for the for the temperature temperature outline hatching (° C.) (° C.) (watts) (watts) Example 1 180 158 16 24 Comparative 180 158 16 24 example 2 Comparative 180 158 16 24 example 3 Comparative 180 158 16 24 example 4 Example 5 180 158 16 24

(18) The parts manufactured by laser sintering of the various compositions are, in all the tests, tensile test specimens which are dumbbells with dimensions of l50*20*3 mm of type 1B.

(19) In comparative tests 2 and 3, the passage through a 3D printing machine or device is difficult (Cp2) or even impossible (Cp3) due to a nonconforming form factor of the fibers, respectively 15 (too large) and 3.6 (too small). In addition, the mechanical properties of the 3D parts obtained are inadequate, the elongation at break being too low in the case of Cp2.

(20) In comparative test 4 (Cp4), the presence of long fibers (fiber length of greater than 500 μm) is incompatible with the 3D printing process. In addition, the breaking stress of the 3D parts is inadequate.

(21) In contrast, the passage through a 3D machine takes place very simply for the compositions of examples 1 and 5 (Ex1 and Ex5) according to the invention.

(22) Surface Appearance of the 3D Objects Obtained:

(23) Examples 1 and 5 according to the invention exhibit a regular, smooth and homogeneous surface appearance with precise edges.

(24) Comparative examples 2 and 4 exhibit an opposite appearance: in particular a degraded surface appearance with the presence of cracks.

(25) Measurement of the Mechanical Properties of the Dumbbells Obtained by Sintering:

(26) The following are obtained for examples 1 and 5 according to the invention, simultaneously: an elastic modulus of at least 3500 MPa, an elongation at break of greater than 6%, a breaking stress of greater than 60 MPa,

(27) the tensile modulus, the elongation and the stress being measured according to the standard ISO 527-2:93-1B; and a heat deflection temperature (HDT) of at least 150° C., determined according to the standard ISO 75-2:2013 (fr) method A.

(28) The use of a powder composition according to the invention in examples 1 and 5, by a 3D printing process, makes it possible to directly obtain reinforced parts, of good definition and with mechanical properties compatible with use in the automobile industry or the aeronautical industry.

(29) Measurement of the Modulus of a “Cp6” Dumbbell Obtained by Injection Molding of the Same Composition as in Example 1: =>Modulus of the Ex1 parts obtained by laser sintering=3800 MPa =>Modulus of the Cp6 parts obtained by injection molding in a microextruder=2500 MPa

(30) These results correspond to a PA11 powder additivated by dry blending with 25% of glass fibers.

(31) The coupling [polyamide 11 powder+glass fibers with a dimension according to the invention] works much better in 3D printing (additive manufacturing) than in injection molding: for one and the same fiber and one and the same composition according to the invention, the modulus of the manufactured object is much greater in laser sintering than in injection molding.

(32) For one and the same PA powder containing glass fibers in accordance with the invention, the mechanical properties obtained in laser sintering are superior to those obtained in injection molding.

(33) An example 6 (Ex6) according to the invention was carried out by mixing the PA11 powder with 40% by weight of fibers as used in examples 1 and 5 with regard to the total weight of the composition.

(34) The composition obtained was passed through the Laser Sintering Formiga P100 (EOS) machine under conditions similar to those described above in order to manufacture tensile test specimens which are dumbbells with dimensions of l50*20*3 mm.sup.3 of type 1B (standard ISO 527-2 1B) in the XY position.

(35) The mechanical properties of the test specimens obtained, measured as indicated above, are summarized in the following table 5:

(36) TABLE-US-00005 TABLE 5 Ex6 Elastic modulus 5260 MPa HDT 180-182.5° C. Breaking stress  62 MPa

(37) Two examples 7 and 8 (Ex7, Ex8) according to the invention based on PA12 were carried out and compared with comparative examples 9 and 10 (Cp9, Cp10).

(38) Example 7 and comparative example 9 comprise Orgasol PA12 (Arkema). Example 8 and comparative example 10 comprise PA12 obtained differently by dissolution/precipitation.

(39) A mixture is produced from the PA12 powder in a similar manner to that which was described above with 30% by weight, with respect to the total weight of the mixture, of glass fibers identical to those of examples 1 and 5 for examples 7 and 8 and with 30% by weight, with respect to the total weight of the mixture, of glass fibers with a length greater than 1 mm for comparative examples 9 and 10.

(40) The compositions obtained were passed through the Laser Sintering Formiga P100 (EOS) machine under conditions similar to those described above in order to manufacture tensile test specimens which are dumbbells with dimensions of l50*20*3 mm.sup.3 of type 1B (standard ISO 527-2 1B) in the XY position.

(41) Construction is impossible with the compositions of comparative examples 9 and 10, which do not pass through the machine.

(42) The results for examples 7 and 8 are presented in table 6 below:

(43) TABLE-US-00006 TABLE 6 Ex7 Ex8 Along the Along the Along the Along the X axis Y axis X axis Y axis Parallel Perpendicular Parallel Perpendicular stress stress stress stress Elastic 4500 MPa 3000 MPa 4500 MPa 3048 MPa modulus Breaking stress  60 MPa /  54 MPa  40 MPa Elongation at 4.4% 5.7% 3.3% 3.4% break