THERMOPLASTIC POLYMER COMPOSITION FOR CONSTRUCTING 3D ARTICLES

Abstract

The invention relates to a composition for the layer-by-layer building of a three-dimensional article by sintering of the composition brought about by electromagnetic radiation, the composition comprising a semicrystalline thermoplastic polymer powder and at least one wax, the wax having a dropping point which is greater than the crystallization temperature of the semicrystalline thermoplastic polymer, said composition in addition optionally comprising a flow agent.

The invention also relates to a process for the preparation of said composition and also to its use for the layer-by-layer building of a three-dimensional article.

Claims

1. A composition for the layer-by-layer building of a three-dimensional (3D) article by sintering of the composition brought about by electromagnetic radiation, the composition comprising: a semicrystalline thermoplastic polymer powder; a wax, the wax having a dropping point which is greater than the crystallization temperature (Ct) of the semicrystalline thermoplastic polymer; and optionally a flow agent, wherein the wax is not a fatty acid salt or a metallic soap.

2. The composition as claimed in claim 1, in which the wax is chosen from polyolefin waxes, waxes of vegetable or animal origin, and also their mixtures.

3. The composition as claimed in claim 2, in which the wax is chosen from polyethylene and polypropylene waxes, polytetrafluoroethylene waxes, ketone waxes, acid waxes, partially esterified acid waxes, acid anhydride waxes, ester waxes, aldehyde waxes, amide waxes, their derivatives and also their mixtures.

4. The composition as claimed in claim 1, in which the semicrystalline thermoplastic polymer is chosen from a polyamide, a homopolymer or copolymer of vinylidene fluoride (PVDF), a copolymer comprising polyamide blocks and comprising polyether blocks (PEBA), a thermoplastic polyurethane (TPU), a copolymer comprising polyester blocks and comprising polyether blocks (COPE), and their mixtures.

5. The composition as claimed in claim 4, in which the semicrystalline thermoplastic polymer is an elastomer chosen from a PEBA, a TPU, a COPE, and their mixtures.

6. The composition as claimed in claim 4, in which the polyamide is chosen from polyamide (PA) 11, PA 12 or PA 6.

7. The composition as claimed in claim 4, in which the polyamide blocks of the PEBA are PA 6, PA 11, PA 12, PA 610, PA 1010 or PA 1012 blocks; and/or in which the polyether blocks of the PEBA are blocks resulting from PEG (polyethylene glycol), PPG (propylene glycol), PO3G (polytrimethylene glycol) or PTMG (polytetrahydrofuran).

8. The composition as claimed in claim 1, in which the wax is present at a content of 0.1% to 20% by weight of the total composition.

9. The composition as claimed in claim 1, in which the dropping point of the wax is greater than the crystallization temperature of the semicrystalline thermoplastic polymer by at least 5° C.

10. The composition as claimed in claim 1, in which the dropping point of the wax is greater than the melting point of the semicrystalline thermoplastic polymer by at most 30° C.

11. The composition as claimed in claim 1, in which the flow agent is present at a content of less than or equal to 5% by weight of the total composition.

12. The composition as claimed in claim 11, in which the flow agent is chosen from: silicas, hydrated silicas, vitreous silicas, fumed silicas or pyrogenic silicas; glassy oxides, glassy phosphates or glassy borates, alumina, amorphous alumina, TiO.sub.2, calcium silicates, magnesium silicates, talc, mica, kaolin, attapulgite and their mixtures.

13. A method for layer-by-layer building of a 3D article by sintering, the method comprising depositing the composition as claimed in claim 1 onto a horizontal plate and sintering the composition with electromagnetic radiation.

14. The method as claimed in claim 13, further comprising reusing the composition to create successive layers of the 3D article.

15. A 3D article manufactured from the method of claim 13.

16. A method of increasing cohesion of a bed of semicrystalline thermoplastic polymer powder for sintering processes, the method comprising adding a wax to the bed of semicrystalline thermoplastic polymer powder, wherein the wax is not a fatty acid salt or a metallic soap.

17. A method of improving the recyclability of semicrystalline thermoplastic polymer powders used for sintering processes, the method comprising adding a wax to the semicrystalline thermoplastic polymer powders, wherein the wax is not a fatty acid salt or a metallic soap.

18. The method as claimed in claim 16, in which the wax has a dropping point which is greater than a crystallization temperature (Ct) of the semicrystalline thermoplastic polymer.

Description

EXAMPLES

Example 1

[0247] Various powders of PEBA copolymers are optionally mixed with a flow agent (silica) at a content of 1% (for polymer A) or 0% (for polymer B) by weight and optionally with a wax at a content of 1% by weight.

[0248] The table below comprises the different PEBAs used in the context of this example.

TABLE-US-00001 TABLE 1 Composition of the polymers used PEBA polymers A B Polyamide blocks PA 11 PA 12 Molar mass of the polyamide 600 5000 blocks (g/mol) Polyether blocks PTMG PTMG Molar mass of the polyether 1000 250 blocks (g/mol) Ratio by weight 0.6 20 Crystallization temperature 68 130 Ct (° C.)

[0249] Thus, the polymers A and B were mixed with flow agent and with a wax so as to form the compositions 1 to 11. These compositions were used for the manufacture of three-dimensional articles.

TABLE-US-00002 TABLE 2 Composition of polymer powder and wax which were studied Observation during the Dropping point passage of the wax through the Composition Polymer Wax (° C.) machine 1 A — — Sinking of the object 2 A Crayvallac 151 OK WN1135 3 A Crayvallac 110 OK WN1495 4 A Crayvallac 145 OK WN1265 5 A Ceridust 9615A 140 OK 6 A Ceridust 8020 74 OK 7 B — — Sinking of the object 8 B Ceridust 9615A 140 OK 9 B Ceridust 8020 74 Powder agglomerates 10 A sodium 75 Sinking of the (composition montanate object without wax) 11 A calcium 125 Sinking of the (composition stearate and object without wax) magnesium stearate

[0250] It was observed that the presence of wax having a dropping point greater than the Ct of the polymer makes it possible for the composition to pass through a sintering machine so as to obtain 3D articles (compositions 2 to 6 and 8). The absence of wax does not make it possible for the composition to pass through the sintering machine (compositions 1 and 7). In the case of the composition 9, it was found that, when the dropping point of the wax is lower than the Ct of the polymer, the manufacture of 3D articles was not possible.

[0251] In the case of the wax-free compositions 10 and 11, it was found that the use of the salts did not make it possible to increase the working window or to ensure the cohesion of the bed; the manufacture of 3D articles was not possible.

Example 2

[0252] A PA 12 powder is mixed with silica at a content of 0.15%. This powder has a Mp equal to 180° C. and a Ct equal to 147° C., which are measured according to the standard ISO 11357.

[0253] This powder is dry mixed with a wax so as to form the compositions 1 and 2. These compositions were used for the manufacture of three-dimensional articles.

[0254] The wax used is a polyhydroxyalkanoate (PHA), which product is sold under the brand name Ceraflour 1000® by BYK.

TABLE-US-00003 Wax (dropping Composition Polymer point = 175° C.) 1 PA 12   0% 2 PA 12 2.0%

[0255] The working window is determined for the compositions 1 and 2.

TABLE-US-00004 Composition Working window 1 161-163° C. 2 155-163° C.

[0256] For the composition 1, a sinking of the parts is observed below 160° C.

[0257] The composition 2 makes possible a building of three-dimensional objects over a wider temperature range; thus this formulation has a greater working window.

[0258] Furthermore, it has been observed that the addition of the wax accelerates the crystallization of the polymer, namely the crystallization temperature becomes higher. This effect is visible by melting the polymer at 220° C. and by then observing the isothermal crystallization in DSC at 160° C. It is seen that the rate of crystallization of the composition 2 is greater than that of the wax-free composition 1. Surprisingly, even though the crystallization temperature is higher, the presence of wax makes it possible however to carry out the printing below 160° C.