Thermoplastic polymer powder for 3D printing with improved recyclability

Abstract

A powder intended for 3D printing, based on thermoplastic polymer, wherein it contains at least 0.1% by weight of at least one thioether antioxidant relative to the total weight of powder. Also, a process for stabilizing the color of a powder based on polymer in a 3D printing process, in which at least 0.1% by weight of at least one thioether antioxidant is incorporated relative to the total weight of powder.

Claims

1. A powder intended for 3D printing, based on thermoplastic polymer, wherein the powder contains at least 0.1% by weight of at least one thioether antioxidant relative to the total weight of powder, and wherein the at least one thioether antioxidant is chosen from: dilauryl thiodipropionate (DLTDP), ditridecyl thiodipropionate (DTDTDP), distearyl thiodipropionate (DSTDP), dimyristyl thiodipropionate (DMTDP), pentaerythrityl tetrakis(3-dodecylthiopropionate or 3-laurylthiopropionate) or mixtures thereof.

2. The powder as claimed in claim 1, in which said at least one thioether antioxidant pentaerythrityl tetrakis(3-dodecylthiopropionate or 3-laurylthiopropionate).

3. The powder as claimed in claim 1, in which said at least one thioether antioxidant represents from 0.1% to 5%, relative to the total weight of powder representing 100%.

4. The powder as claimed in claim 1, in which said thermoplastic polymer is chosen from: polyolefin, polyethylene, polypropylene, polyvinyl chloride, polyacetal, polystyrene, polyimide, polysulfone, poly(N-methylmethacrylimide), polymethyl methacrylate, polyvinylidene fluoride, ionomer, polyether ketone, polyaryl ether ketone, polyamide, polyether, polyester, polydimethylsiloxane, polycarbonate and mixtures thereof in the form of alternating, statistical or block copolymers.

5. The powder as claimed in claim 1, in which said polymer comprises at least one polyamide chosen from PA11, PA12, PA10.10, aliphatic polyamides resulting from the condensation of an aliphatic diamine containing from 6 to 12 carbon atoms and of an aliphatic diacid containing from 9 to 12 carbon atoms and copolyamides 11/12 containing either more than 90% of units 11 or more than 90% of units 12.

6. (canceled)

7. The powder as claimed in claim 1, in which the polymer is in the form of a powder with a volume-median diameter D50 in the range from 10 to 150 μm.

8. A process for stabilizing the color of a powder based on thermoplastic polymer in a 3D printing process, in which at least 0.1% by weight of at least one thioether antioxidant is incorporated relative to the total weight of powder.

9. A process for increasing and then stabilizing the inherent viscosity of a powder based on thermoplastic polymer in a 3D printing process, in which at least 0.1% by weight of at least one thioether antioxidant is incorporated relative to the total weight of powder.

10. The process as claimed in claim 8, in which said at least one thioether antioxidant is chosen from: dilauryl thiodipropionate (DLTDP), ditridecyl thiodipropionate (DTDTDP), distearyl thiodipropionate (DSTDP), dimyristyl thiodipropionate (DMTDP), pentaerythrityl tetrakis(3-dodecylthiopropionate or 3-laurylthiopropionate), and mixtures thereof.

11. The process as claimed in claim 8, in which said at least one thioether antioxidant represents from 0.1% to 5%, relative to the total weight of powder representing 100%.

12. The process as claimed in claim 8, in which the thioether is incorporated by at least one of the following methods: impregnation of the polymer in an aqueous dispersion of the thioether, addition of thioether during the synthesis of the polymer, notably at the start or at the end of the synthesis, by blending by compounding, or during any step of a powder manufacturing process starting with said polymer, notably by dissolution-precipitation of polymer in a solvent containing the thioether.

13. The process as claimed in claim 8, in which said thermoplastic polymer is chosen from: polyolefin, polyethylene, polypropylene, polyvinyl chloride, polyacetal, polystyrene, polyimide, polysulfone, poly(N-methylmethacrylimide), polymethyl methacrylate, polyvinylidene fluoride, ionomer, polyether ketone, polyaryl ether ketone, polyamide, polyether, polyester, polydimethylsiloxane, polycarbonate and mixtures thereof in the form of alternating, statistical or block copolymers.

14. The process as claimed in claim 8, in which said polymer comprises at least one polyamide (homopolyamide or copolyamide).

15. The process as claimed in claim 8, in which the polyamide is in the form of a powder with a volume-median diameter D50 in the range from 10 to 150 μm.

16. A 3D printing process using a powder as claimed in claim 1.

17. (canceled)

18. A process for manufacturing an article by sintering using a powder as claimed in claim 1, in which the unsintered powder is recovered and reused.

19-21. (canceled)

22. The powder as claimed in claim 1, wherein the powder comprises an antioxidant mixture including the at least one thioether antioxidant, wherein the thioether antioxidant mixture is more than 55% by weight of the antioxidant mixture.

23. The powder as claimed in claim 1, wherein the thermoplastic powder also comprises a copolyamide of polyamides 11 and 12 containing either more than 90% of units 11 or more than 90% of units 12.

Description

EXAMPLES

Example 1

[0124] Materials Used:

[0125] Polymer: Polyamide (PA):

[0126] powder of PA 11 synthesized by grinding a polymer obtained by polycondensation of 11-aminoundecanoic acid, mixed with a standard phenolic antioxidant for PA (Irganox 245 (BASF) at 0.3% or Palmarole AO.OH.98 Ultrafine (Palmarole) at 0.6% for the comparative example without antioxidant intended for combating aging).

[0127] Antioxidants Intended for Combating Aging:

[0128] dilauryl thiodipropionate (DLTDP), sold by Songnox;

[0129] pentaerythrityl tetrakis(3-dodecylthiopropionate), sold by Adeka;

[0130] diphosphonite antioxidant, sold by Clariant (P-EPQ)

[0131] 1.1—Evaluation of the Flowabilities at Room Temperature (23° C.) of the Two Formulations:

[0132] The flowability test consists in measuring the flow time of 150 g of powder through a funnel, according to the standard ISO 6186: 1998(E) Method A.

[0133] The test is performed on the powder at room temperature, the measurements are taken with a funnel with an aperture of 15 mm. The results are indicated in table 1 below:

TABLE-US-00001 TABLE 1 Flowability at room temperature (time in seconds) Ø 15 mm PA11 (viscosity 1.12) + 30 s 0.5% DLTDP PA11 (viscosity 1.12) + 34 s 0.5% pentaerythrityl tetrakis(3- dodecylthiopropionate)

[0134] 1.2—Aging Test

[0135] The test consists in exposing the polyamide powder to a temperature 10 to 30° C. below the melting point Tf of the pure polyamide (from Tf−30° C. to Tf−10° C.) in a glass bottle placed in an air-ventilated oven, in particular at 180° C. in this example.

[0136] This test simulates the exposure conditions to which a powder may be subjected in a 3D machine, for 1 run or several runs, according to the exposure times.

[0137] The exposure times are from 0 to 90 hours, for example 48 hours (1 run), 72 hours (2 runs) (one bottle per sample withdrawn).

[0138] 1.2-1 Yellowness Index (YI)

[0139] The measurements are taken on a Konica Minolta spectrocolorimeter with the illuminant D65 at 10° in SCI mode according to the standard ASTM YI (E313-96) (D65).

TABLE-US-00002 TABLE 2 YI Examples according to the invention Comparative examples Thermoplastic polymer PA11 PA11 PA11 PA11 Additive 0.5% pentaerythrityl tetrakis(3- 0.5% P- dodecylthiopropionate) 0.5% DLTDP — EPQ T.sub.0 1.5 1.4 2.3 2.5 48 h 8.7 13.0 — 72 h 28.7 40.6 Measurement 48.1 impossible

[0140] The thioether antioxidant 3-dodecylthiopropionate is more efficient than the thioether antioxidant DLTDP in terms of preventing yellowing, which is itself more efficient than the diphosphonite antioxidant P-EPQ (non-thioether).

[0141] 1.2-2 Inherent Viscosity of the PA Powder

[0142] The inherent viscosity is measured at 20° C., in solution at 0.5% by mass in meta-cresol according to the standard ISO 307:2007.

TABLE-US-00003 TABLE 3 Inherent viscosity Examples according to the invention Comparative examples Thermoplastic polymer PA11 PA11 PA11 PA11 Additive 0.5% pentaerythrityl tetrakis(3- 0.5% 0.5% P- dodecylthiopropionate) DLTDP — EPQ T.sub.0 1.21 1.21 1.12 1.09 48 h 1.55 1.57 — 72 h 1.44 1.37 Measurement 0.89 impossible

[0143] The thioether antioxidant 3-dodecylthiopropionate is slightly more efficient than the antioxidant DLTDP. The performance qualities obtained with the two thioether antioxidants after 72 hours of aging are markedly better than those obtained for the diphosphonite antioxidant P-EPQ (non-thioether).

Example 2

[0144] Materials Used:

[0145] Polymer: Polyamide (PA):

[0146] powder of PA 12 synthesized by grinding a polymer obtained by direct polymerization of lauryllactam mixed with a standard phenolic antioxidant for PA (Irganox 245 (BASF) at 0.3% for the example, or Lowinox 44B25 (Addivant) at 0.5% for the comparative example).

[0147] Antioxidants Intended for Combating Aging:

[0148] pentaerythrityl tetrakis(3-dodecylthiopropionate), sold by Adeka.

[0149] The powder and the antioxidant are dry-blended.

[0150] Aging Test

[0151] The polyamide powder is exposed to a temperature of 170° C. in an oven (FGE 140) in air, for 72 hours.

[0152] 2.1. Yellowness Index (YI)

[0153] The measurements are taken on a Konica Minolta spectrocolorimeter with the illuminant D65 at 10° in SCI mode according to the standard ASTM YI (E313-96) (D65).

TABLE-US-00004 TABLE 4 YI Example according to the invention Comparative examples Thermoplastic polymer PA12 PA12 Additive 0.5% pentaerythrityl tetrakis(3- dodecylthiopropionate) — T.sub.0 1.7 2.4 72 h 11.2 12.2

[0154] 2.2 Inherent Viscosity of the PA Powder

[0155] The inherent viscosity is measured at 20° C., in solution at 0.5% by mass in meta-cresol according to the standard ISO 307:2007.

TABLE-US-00005 TABLE 5 Inherent viscosity Examples according to the invention Comparative examples Thermoplastic polymer PA12 PA12 Additive 0.5% pentaerythrityl tetrakis(3- dodecylthiopropionate) — T.sub.0 1.28 1.28 72 h 1.23 1.22

[0156] In summary, the process according to the invention, by controlling the nature and the amount of antioxidant in the polyamide powder that is employed during the first sintering construction, makes it possible to increase the recyclability of the powder, and to obtain a powder in which the change in color, notably the yellowing, and the change in molecular mass undergone by the powder not melted during each construction, were controlled beforehand in a simple manner in the powder that is employed during the first construction.