Additive manufacturing method for making a three-dimensional object using selective laser sintering

Abstract

The present disclosure relates to an additive manufacturing (AM) method for making a three-dimensional (3D) object, comprising a) the provision of providing a powdered polymer material (M) comprising at least one poly(ether ether ketone) (PEEK) polymer, and at least one poly(aryl ether sulfone) (PAES) polymer, b) the deposition of successive layers of the powdered polymer material; and c) the selective sintering of each layer prior to the deposition of the subsequent layer, wherein the powdered polymer material (M) is heated before step c) to a temperature Tp (° C.): Tp<Tg+40, wherein Tg (° C.) is the glass transition temperature of the PAES polymer, as measured by differential scanning calorimetry (DSC) according to ASTM D3418.

Claims

1. An additive manufacturing method for making a three-dimensional (3D) object, comprising: a) providing a powdered polymer material (M) comprising: from 55 to 95 wt. % of at least one poly(ether ether ketone) (PEEK) polymer, wherein the PEEK polymer comprises at least 50 mol. % of recurring units (R.sub.PEEK) of formula (J-A), based on the total number of moles in the polymer: ##STR00016## where R′, at each location, is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine and quaternary ammonium; where j′, for each R′, is independently zero or an integer ranging from 1 to 4; and from 5 to 45 wt. % of at least one poly(aryl ether sulfone) (PAES) polymer, based on the total weight of the powdered polymer material (M), wherein the PAES polymer comprising at least 50 mol. % of recurring units (R.sub.pAEs) of formula (K), based on the total number of moles in the polymer: ##STR00017## where R, at each location, is independently selected from the group consisting of a halogen, an alkyl, an alkenyl, an alkynyl, an aryl, an ether, a thioether, a carboxylic acid, an ester, an amide, an imide, an alkali or alkaline earth metal sulfonate, an alkyl sulfonate, an alkali or alkaline earth metal phosphonate, an alkyl phosphonate, an amine, and a quaternary ammonium; where h, for each R, is independently zero or an integer ranging from 1 to 4; and where T is selected from the group consisting of a bond and a group—C(Rj)(Rk)—, where Rj and Rk, equal to or different from each other, are selected from the group consisting of a hydrogen, a halogen, an alkyl, an alkenyl, an alkynyl, an ether, a thioether, a carboxylic acid, an ester, an amide, an imide, an alkali or alkaline earth metal sulfonate, an alkyl sulfonate, an alkali or alkaline earth metal phosphonate, an alkyl phosphonate, an amine, and a quaternary ammonium; b) depositing successive layers of the powdered polymer material (M); and c) selectively sintering each layer prior to deposition of the subsequent layer, wherein the powdered polymer material (M) is heated before step c) to a temperature Tp (° C.):
Tp<Tg+40 wherein Tg (° C.) is the glass transition temperature of the PAES polymer, as measured by differential scanning calorimetry (DSC) according to ASTM D3418.

2. The method of claim 1, wherein the powdered polymer material (M) has a dos-value ranging between 25 and 90 μm, as measured by laser scattering in isopropanol.

3. The method of claim 1 wherein the PAES polymer is a poly(biphenyl ether sulfone) (PPSU) polymer, wherein PPSU denotes a polymer comprising at least 50 mol. % of recurring units (R.sub.ppsu) of formula (L), based on the total number of moles in the PPSU polymer: ##STR00018## where R, at each location, is independently selected from a halogen, an alkyl, an alkenyl, an alkynyl, an aryl, an ether, a thioether, a carboxylic acid, an ester, an amide, an imide, an alkali or alkaline earth metal sulfonate, an alkyl sulfonate, an alkali or alkaline earth metal phosphonate, an alkyl phosphonate, an amine, and a quaternary ammonium; and where h, for each R, is independently zero or an integer ranging from 1 to 4″.

4. The method of claim 1, wherein the powdered polymer material (M) is heated before step c) to a temperature Tp (° C.):
Tp<Tg+30 wherein Tg (° C.) is the glass transition temperature of the PAES polymer, as measured by differential scanning calorimetry (DSC) according to ASTM D3418.

5. The method of claim 1, wherein the powdered polymer material (M) comprises: from 56 to 80 wt. % of at least one poly(ether ether ketone) (PEEK) polymer, and from 20 to 44 wt. % of at least one poly(aryl ether sulfone) (PAES) polymer, based on the total weight of the powdered polymer material (M).

6. The method of claim 1, wherein the powdered polymer material (M) further comprises 0.01 to 10 wt. % of a flow agent.

7. The method of claim 1, wherein the PAES has a Tg ranging from 160 and 250° C., as measured by differential scanning calorimetry (DSC) according to ASTM D3418.

8. The method of claim 1, wherein the powdered polymer material (M) is obtained by grinding a blend of at least the PEEK polymer and the PAES polymer, the blend being optionally cooled down to a temperature below 25° C. before and/or during grinding.

9. The method of claim 1, wherein step c) comprises selective sintering by means of an electromagnetic radiation of the powder.

10. A method for manufacturing a three-dimensional (3D) object comprising using selective laser sintering (SLS) with a powdered polymer material (M) having a d.sub.0.5 value ranging from 25 to 90 μm and comprising: from 55 to 95 wt. % of at least one poly(ether ether ketone) (PEEK) polymer, wherein the PEEK polymer denotes a polymer comprising at least 50 mol. % of the recurring units of formula (J″-A): ##STR00019## the mol. % being based on the total number of moles in the polymer from 5 to 45 wt. % of at least one poly(aryl ether sulfone) (PAES) polymer, based on the total weight of the powdered polymer material (M), wherein the PAES polymer denotes a polymer comprising at least 50 mol. % of recurring units of formula (K′), based on the total number of moles in the polymer: ##STR00020## and a flow agent selected from the group consisting of silicas, aluminas and titanium oxide.

11. The method of claim 1, wherein the PAES polymer is a polysulfone (PSU) polymer, wherein PSU denotes a polymer comprising at least 50 mol. % recurring units (RPSU) of formula (N), the mol. % being based on the total number of moles in the polymer: ##STR00021## where R, at each location, is independently selected from a halogen, an alkyl, an alkenyl, an alkynyl, an aryl, an ether, a thioether, a carboxylic acid, an ester, an amide, an imide, an alkali or alkaline earth metal sulfonate, an alkyl sulfonate, an alkali or alkaline earth metal phosphonate, an alkyl phosphonate, an amine, and a quaternary ammonium; and where h, for each R, is independently zero or an integer ranging from 1 to 4″.

12. The method of claim 1, wherein the PEEK has at least 50 mol. % of recurring units of formula (J″-A): ##STR00022## the mol. % being based on the total number of moles in the polymer.

13. The method of claim 1, wherein the PEEK has at least 80 mol. % of recurring units of formula (J″-A): ##STR00023## the mol. % being based on the total number of moles in the polymer.

14. The method of claim 1, wherein the PEEK has at least 90 mol. % of recurring units of formula (J″-A): ##STR00024## the mol. % being based on the total number of moles in the polymer.

15. The method of claim 1, wherein the PEEK has at least 95 mol. % of recurring units of formula (J″-A): ##STR00025## the mol. % being based on the total number of moles in the polymer.

16. The method of claim 1, wherein the PEEK is a copolymer that has at least 50 mol. % of recurring units of formula (J″-A): ##STR00026## the mol. % being based on the total number of moles in the polymer, and wherein the PEEK has less than 50 mol. % of recurring units of formula (J″-D): ##STR00027## the mol. % being based on the total number of moles in the polymer.

17. The method of claim 1, wherein the PAES polymer is a PPSU comprising at least 50 mol. % of recurring units of formula (L″): ##STR00028## the mol. % being based on the total number of moles in the polymer.

18. The method of claim 1, wherein the PAES polymer is a PPSU comprising at least 80 mol. % of recurring units of formula (L″): ##STR00029## the mol. % being based on the total number of moles in the polymer.

19. The method of claim 1, wherein the PAES polymer is a PPSU comprising at least 90 mol. % of recurring units of formula (L″): ##STR00030## the mol. % being based on the total number of moles in the polymer.

20. The method of claim 1, wherein the PAES polymer is a PPSU comprising at least 95 mol. % of recurring units of formula (L″): ##STR00031## the mol. % being based on the total number of moles in the polymer.

21. The method of claim 1, wherein the PAES polymer is a PSU comprising at least 50 mol. % of recurring units of formula (N″): ##STR00032## the mol. % being based on the total number of moles in the polymer.

22. The method of claim 1, wherein the PAES polymer is a PSU comprising at least 80 mol. % of recurring units of formula (N″): ##STR00033## the mol. % being based on the total number of moles in the polymer.

23. The method of claim 1, wherein the PAES polymer is a PSU comprising at least 90 mol. % of recurring units of formula (N″): ##STR00034## the mol. % being based on the total number of moles in the polymer.

24. The method of claim 1, wherein the PAES polymer is a PSU comprising at least 95 mol. % of recurring units of formula (N″): ##STR00035## the mol. % being based on the total number of moles in the polymer.

Description

EXAMPLES

(1) The disclosure will be now described in more detail with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the disclosure.

Starting Materials

(2) PEEK #1: a poly(ether ether ketone) (PEEK) having a MFI of 36 g/10 min (400° C./2.16 kg), prepared according to the following process:

(3) In a 500 ml 4-neck reaction flask fitted with a stirrer, a N2 inlet tube, a Claisen adapter with a thermocouple plunging in the reaction medium, and a Dean-Stark trap with a condenser and a dry ice trap were introduced 128 g of diphenyl sulfone, 28.6 g of p-hydroquinone, and 57.2 g of 4,4′-difluorobenzophenone.

(4) The reaction mixture was heated slowly to 150° C. At 150° C., a mixture of 28.43 g of dry Na.sub.2CO.sub.3 and 0.18 g of dry K.sub.2CO.sub.3 was added via a powder dispenser to the reaction mixture over 30 minutes. At the end of the addition, the reaction mixture was heated to 320° C. at 1° C./minute.

(5) After 15 to 30 minutes, when the polymer had the expected Mw, the reaction was stopped by the introduction of 6.82 g of 4,4′-difluorobenzophenone to the reaction mixture while keeping a nitrogen purge on the reactor. After 5 minutes, 0.44 g of lithium chloride were added to the reaction mixture. 10 minutes later, another 2.27 g of 4,4′-difluorobenzophenone were added to the reactor and the reaction mixture was kept at temperature for 15 minutes. The reactor content was then cooled.

(6) The solid was broken up and ground. The polymer was recovered by filtration of the salts, washing and drying.

(7) TABLE-US-00001 TABLE 1 PEEK #1 MFI (400° C./2.16 kg) 36 g/10 min Tm (° C.) 345 Tg (° C.) 150

(8) PEEK #2: a poly(ether ether ketone) (PEEK) having a MFI of 3 g/10 min (400° C./2.16 kg), prepared according to the same process than PEEK #1, except that the reaction was stopped later.

(9) TABLE-US-00002 TABLE 2 PEEK #2 MFI (400° C./2.16 kg) 3 g/10 min Tm (° C.) 345 Tg (° C.) 150

(10) PPSU: a poly(biphenyl ether sulfone) (PPSU) with a MFI of 17 g/10 min (365° C./5 kg), prepared according to the following process:

(11) The synthesis of the PPSU was achieved by the reaction in a 1 L flask of 83.8 g of 4,4′-biphenol (0.450 mol), 131.17 g of 4,4′-dichlorodiphenyl sulfone (0.457 mol) dissolved in a mixture of 400 g of sulfolane with the addition of 66.5 g (0.481 mol) of dry K.sub.2CO.sub.3.

(12) The reaction mixture was heated up to 210° C. and maintained at this temperature until the polymer had the expected Mw. An excess of methyl chloride was then added to the reaction.

(13) The reaction mixture was diluted with 600 g of MCB. The poly(biphenyl ether sulfone) was recovered by filtration of the salts, coagulation, washing and drying.

(14) TABLE-US-00003 TABLE 3 PPSU MFI (365° C./5 kg) 17 g/10 min Tg (° C.) 220

(15) PSU #1: a polysulfone (PSU) with a MFI of 6.5 g/10 min (343° C./2.16 kg), prepared according to the following process:

(16) The synthesis of the PSU was achieved by the reaction in a 1 L flask of 114.14 g (0.5 mol) of bisphenol A dissolved in a mixture of 247 g of dimethylsulfoxide (DMSO) and 319.6 g of monochlorobenzene (MCB) with an aqueous solution of 79.38 g of sodium hydroxide at 50.34%, followed by distillation of the water to generate a solution of bisphenol A sodium salt free from water by heating the solution up to 140° C. In the reactor was then introduced a solution of 143.59 g (0.5 mol) of 4,4′-dichlorodiphenyl sulfone in 143 g of MCB. The reaction mixture was heated up to 165° C. and maintained at this temperature during 15 to 30 min, until the polymer had the expected Mw. An excess of methyl chloride was then added to the reaction.

(17) The reaction mixture was diluted with 400 mL of MCB and then cooled to 120° C. 30 g of methyl chloride was added over 30 min. The polysulfone was recovered by filtration of the salts, washing and drying.

(18) TABLE-US-00004 TABLE 4 PSU MFI (343° C./2.16 kg) 6.5 g/10 min Tg (° C.) 190

Test Methods

Thermal Transitions (Tg, Tm)

(19) The glass transition and melting temperatures of the polymers were measured using differential scanning calorimetry (DSC) according to ASTM D3418 employing a heating and cooling rate of 20° C./min. Three scans were used for each DSC test: a first heat up to 400° C., followed by a first cool down to 30° C., followed by a second heat up to 400° C. The Tg and the Tm were determined from the second heat up. DSC was performed on a TA Instruments DSC Q20 with nitrogen as carrier gas (99.998% purity, 50 mL/min).

MFI

(20) The melt flow indices of the polymers were measured according to ASTM D-1238, using a weight of either 2.16 kg or 5 kg and a temperature of 400° C., 365° C. or 343° C. The measurements were conducted on a Dynisco D4001 Melt Flow Indexer.

PSD (D.SUB.0.5.)

(21) The PSD (volume distribution) of the powdered polymer materials were determined by an average of 3 runs using laser scattering Microtrac S3500 analyzer in wet mode (128 channels, between 0.0215 and 1408 μm). The solvent was isopropanol with a refractive index of 1.38 and the particles were assumed to have a refractive index of 1.59. The ultrasonic mode was enabled (25 W/60 seconds) and the flow was set at 55%.

Blend Compounding

(22) The formulations were melt compounded using a 26 mm diameter Coperion® ZSK-26 co-rotating partially intermeshing twin screw extruder having an L/D ratio of 48:1. The barrel sections 2 through 12 and the die were heated to set point temperatures as follows:

(23) Barrels 2-7: 350 to 360° C.

(24) Barrels 8-12: 360° C.

(25) Die: 360° C.

(26) The resin blends were fed at barrel section 1 using a gravimetric feeder at throughput rates in the range 30-40 lb/hr. The extruder was operated at screw speeds of around 200 RPM. Vacuum was applied at barrel zone 10 with a vacuum level of about 27 inches of mercury. A single-hole die was used for all the compounds to give a filament approximately 2.6 to 2.7 mm in diameter and the polymer filament exiting the die was cooled in water and fed to the pelletizer to generate pellets approximately 2.7 mm in length.

Powdered Polymer Material Preparation

(27) The blended formulations were slowly fed in combination with crushed dry ice into the feed port of a Retsch SR300 rotor mill, fitted with a 0.5 mm opening Conidur screen mounted in the reverse flow position and standard 6-blade rotor with a speed of 10,000 rpm.

(28) The materials were re-mixed with crushed dry ice at 1 part resin and 2 parts dry ice to the Retsch SR300 with a 0.08 mm screen, also in the reverse flow position with a standard 6-blade rotor at 10,000 rpm.

(29) TABLE-US-00005 TABLE 5 Blend 1 Blend 2 PEEK#1/PPSU PEEK#2/PSU 60/40 wt/wt 63/37 wt/wt d.sub.0.5-value (μm) 81.0 71.9

Heat Treatment

(30) The aim of the heat treatments was to simulate long-term printing conditions within the print bed of an SLS printer and evaluate recyclability of the materials. More precisely, the materials were subjected to different heat treatment temperatures for 16 hours in an air convection oven and then tested for their retained sintering (coalescence) capability, thereby simulating a printing cycle. Recyclability was tested by examining remaining particle coalescence ability. Additionally, the powders were evaluated for their aspect and their disaggregation following heat treatments, that-is-to-say their ability to be broken apart by traditional sieving.

(31) Generally speaking, as an example, a color change from off-white to brown, dark brown or black was considered as failing the recyclability requirement. Also, a powder material which could not be broken apart by traditional sieving, after a 16-hour long heat treatment at a certain temperature, was also considered as failing the recyclability requirement.

Hot Stage Microscopy

(32) The aim of the hot stage microscopy tests was to study particle coalescence under experimental conditions that simulate the sintering step of the method for making a 3D object of the present invention, in order to compare sintering behaviour as a function of the exposition of different materials to high-temperature conditions within an air convection oven for 16 hours.

(33) Coalescence was evaluated on a Keyence VHX 600K optical microscope with a digital zoom of 200×. A Linkam T96-PE hot-stage attachment was utilized in order to increase the temperature of the material in order to simulate the increased temperature of the material within an SLS printer upon printing.

(34) The material was heated quickly (100° C./min) to 260° C. Following the rapid pre-heat, the material was subjected to a temperature increase at 20° C./min until reaching 400° C., at which point the temperature was held constant in order to observe coalescence. The temperature of 400° C. hereby simulates the energy source (for example laser) used to sinter selected regions of layer of unfused powder in a SLS equipment.

(35) Coalescence was measured by observing two particles that were adjacent prior to heating. During the heating and isothermal phase at 400° C., the particles were observed to coalesce together, with a neck or bridge, formed between the two during intermediate steps.

Selective Laser Sintering

(36) The aim of selective laser sintering was to examine the ability to sinter the selected materials and examine degree of coalescence of the powder composing the printed object.

(37) Laser sintering was performed on a DTM (now 3D Systems) Sinterstation 2500 Plus using a CO2 laser at a wavelength of 10.6 micrometers.

(38) The material was printed at a temperature between 180 and 200° C. with an exposure laser power between 4 and 40 Watts. The exposure speed was between 0.5 and 3 meters/sec. Printing was optimized using these settings.

Definitions and Results

Disaggregation

(39) 0=Not Aggregated: Powder particles are not closely associated together and the powder is loosely flowing.

(40) 1=Easy Disaggregation: Powder particles are closely associated together but can be easily broken back apart by traditional sieving.

(41) 2=Difficult Disaggregation: Powder particles have slightly fused together and cannot be broken back apart by traditional sieving.

(42) 3=No Disaggregation: Powder particles have fused together with no possible separation except by grinding.

Coalescence

(43) Yes: Particles exhibit rapid coalescence between the temperatures of 355° C. and 365° C. during an increasing temperature ramp with rate of 20° C./min. No: Particles do not exhibit any coalescence between the temperatures of 355° C. and 365° C. during an increasing temperature ramp with rate of 20° C./min.

(44) TABLE-US-00006 TABLE 6 E1 E2 E3 E4c E5c Blend 1 (PEEK#1/PPSU, Tg PPSU = 220° C.) Treatment none 200 230 260 330 temperature (° C.) Corresponding n/a Tg − 20 Tg + 10 Tg + 40 Tg + 110 Tp (° C.) Powder aspect Off- Off- Off- Off- Dark white white white white brown Disaggregation 0 1 1 2 3 Particle Yes Yes Yes Yes* No coalescence *Exhibited extremely slow coalescence instead of rapid coalescence.

(45) The color, the disaggregation and the coalescence ability of the powder of example E1 (no heat treatment) simulates the behaviour of the powder when used for the first time in a SLS printer.

(46) The color, the disaggregation and the coalescence ability of the powder of example E2, which has been submitted to a 16-hour heat treatment at 200° C. (temperature lower than the glass transition of the amorphous polymer of powdered polymer material, i.e. PPSU) and E3, which has been submitted to a 16-hour heat treatment at 230° C. (temperature higher than the glass transition of the amorphous polymer of powdered polymer material, i.e. PPSU) are shown to be comparable to example E1. These results are in themselves unexpected in that the 16-hour long treatment at a temperature above (230° C.) or close (200° C.) to the Tg of the amorphous component of the blend (here PPSU with a Tg of 220° C.) does not significantly affect the resulting powder and makes the powder recyclable.

(47) The powder of example E4c however demonstrates difficult disaggregation and decreased coalescence ability. The powder of example E4C treated 16 hours at a temperature of 260° C. (temperature 40° C. higher than the glass transition of the PPSU polymer) cannot not be recycled.

(48) The powder of example E5c demonstrates a non-acceptable change of color, no possible disaggregation and no coalescence, which make them not recyclable at all.

(49) TABLE-US-00007 TABLE 7 E6 E7 E8c E9c Blend 2 (PEEK#2/PSU, Tg PSU = 190° C.) Treatment none 200 230 330 temperature (° C.) Corresponding n/a Tg + 10 Tg + 40 Tg + 140 Tp (° C.) Powder aspect Off-white Off-white Off-white Black Disaggregation 0 1 2 3 Particle Yes Yes No No coalescence

(50) The color, the disaggregation and the coalescence ability of the powder of example E6 (no heat treatment) simulates the behaviour of the powder when used for the first time in a SLS printer.

(51) The color, the disaggregation and the coalescence ability of the powder of example E7, which has been submitted to a 16-hour heat treatment at 200° C. (temperature higher than the glass transition of the amorphous polymer of powdered polymer material, i.e. PSU in this case) is shown to be comparable to example E6. Again here, the results are unexpected in that the 16-hour long heat treatment at 200° C., above the Tg of the amorphous PSU polymer (190° C.) does not significantly affect the powder blend and makes to polymer combination recyclable.

(52) The powder of examples E8c and E9c however failed the recyclability requirements (disaggregation and coalescence, plus non-acceptable color for E9c).

(53) Example E10: A monolayer of Blend 1, printed with the defined print conditions, exhibits definite coalescence with no possibility of disaggregation. This printed monolayer demonstrates the ability to print at a temperature between 180 and 200° C., which is less than 260° C. (Tg+40). The powder surrounding this printed monolayer remains unsintered and not aggregated.