Processes for producing a shaped body using polyamide blends containing a polyarylether

Abstract

The present invention relates to a process for producing a shaped body by selective laser sintering of a sinter powder (SP). The sinter powder (SP) comprises at least one semicrystalline polyamide, at least one nylon-6I/6T and at least one polyaryl ether. The present invention further relates to a shaped body obtainable by the process of the invention and to the use of a polyaryl ether in a sinter powder (SP) for broadening the sintering window (W.sub.SP) of the sinter powder (SP).

Claims

1. A process for producing a shaped body by selective laser sintering of a sinter powder (SP), wherein the sinter powder (SP) comprises the following components: (A) at least one semicrystalline polyamide comprising at least one unit selected from the group consisting of NH(CH.sub.2).sub.mNH units where m is 4, 5, 6, 7 or 8, CO(CH.sub.2).sub.nNH units where n is 3, 4, 5, 6 or 7, and CO(CH.sub.2).sub.oCO units where o is 2, 3, 4, 5 or 6, (B) at least one nylon-6I/6T, (C) at least one polyaryl ether, wherein component (C) is a polyaryl ether containing units of the general formula (I) ##STR00006## with the following definitions: t, q: each independently 0, 1, 2 or 3, Q, T, Y: each independently a chemical bond or group selected from O, S, SO.sub.2, SO, CO, NN and CR.sup.aR.sup.b where R.sup.a and R.sup.b are each independently a hydrogen atom or a C.sub.1-C.sub.12-alkyl, C.sub.1-C.sub.12-alkoxy or C.sub.6-C.sub.18-aryl group and where at least one of Q, T and Y is-SO.sub.2 and Ar, Ar.sup.1: each independently an arylene group having from 6 to 18 carbon atoms, and wherein a first layer of the sinter powder (SP) is arranged in a powder bed and locally exposed to a laser beam, and wherein the sinter powder (SP) comprises in the range from 20% to 90% by weight of component (A), in the range from 5% to 40% by weight of component (B) and in the range from 5% to 40% by weight of component (C), based in each case on the sum total of the percentages by weight of components (A), (B) and (C).

2. The process according to claim 1, wherein the sinter powder (SP) has a D10 in the range from 10 to 30 m, a D50 in the range from 25 to 70 m and a D90 in the range from 50 to 150 m, wherein the particle sizes of the sinter powder (SP) are determined by a laser diffraction.

3. The process according to claim 1, wherein the sinter powder (SP) has a melting temperature (T.sub.M) in the range from 180 to 270 C., wherein the melting temperature (T.sub.M) is determined by means of dynamic differential calorimetry.

4. The process according to claim 1, wherein the sinter powder (SP) has a crystallization temperature (T.sub.C) in the range from 120 to 190 C., wherein the crystallization temperature (T.sub.C) is determined by means of dynamic differential calorimetry.

5. The process according to claim 1, wherein the sinter powder (SP) has a sintering window (W.sub.SP), where the sintering window (W.sub.SP) is the difference between the onset temperature of melting (T.sub.M.sup.onset) and the onset temperature of crystallization (T.sub.C.sup.onset) and where the sintering window (W.sub.SP) is in the range from 18 to 45 K.

6. The process according to claim 1, wherein the sinter powder (SP) is produced by grinding components (A), (B) and (C) at a temperature in the range from 210 to 195 C.

7. The process according to claim 1, wherein component (A) is selected from the group consisting of PA 6, PA 6.6, PA 6.10, PA 6.12, PA 6.36, PA 6/6.6, PA 6/6I6T, PA 6/6I and PA 6/6T.

8. The process according to claim 1, wherein component (C) is selected from the group consisting of PSU, PESU and PPSU.

9. The process according to claim 1, wherein the sinter powder (SP) additionally comprises at least one additive selected from the group consisting of antinucleating agents, stabilizers, end group functionalizers and dyes.

10. A process for broadening the sintering window (W.sub.SP) of a sinter powder (SP) compared to the sintering window (W.sub.AB) of a mixture of components (A) and (B) which comprises incorporating into the sinter powder at least one polyaryl ether in the sinter powder (SP) comprising the following components: (A) at least one semicrystalline polyamide comprising at least one unit selected from the group consisting of NH(CH.sub.2).sub.mNH units where m is 4, 5, 6, 7 or 8, CO(CH.sub.2).sub.nNH units where n is 3, 4, 5, 6 or 7, and CO(CH.sub.2).sub.oCO units where o is 2, 3, 4, 5 or 6, (B) at least one nylon-6I/6T, (C) at least one polyaryl ether, where the sintering window (W.sub.SP; W.sub.AB) in each case is the difference between the onset temperature of melting (T.sub.M.sup.onset) and the onset temperature of crystallization (T.sub.C.sup.onset), wherein the polyaryl ether contains units of the general formula (I) ##STR00007## with the following definitions: t, q: each independently 0, 1, 2 or 3, Q, T, Y: each independently a chemical bond or group selected from O, S, SO.sub.2, SO, CO, NN and CR.sup.aR.sup.b where R.sup.a and R.sup.b are each independently a hydrogen atom or a C.sub.1-C.sub.12-alkyl, C.sub.1-C.sub.12-alkoxy or C.sub.6-C.sub.18-aryl group and where at least one of Q, T and Y is-SO.sub.2 and Ar, Ar.sup.1: each independently an arylene group having from 6 to 18 carbon atoms, wherein the sinter powder (SP) comprises in the range from 20% to 90% by weight of component (A), in the range from 5% to 40% by weight of component (B) and in the range from 5% to 40% by weight of component (C), based in each case on the sum total of the percentages by weight of components (A), (B) and (C).

Description

EXAMPLES

(1) The following components are used: Semicrystalline polyamide (component (A)):

(2) TABLE-US-00003 (P1) nylon-6 (Ultramid B27, BASF SE) Amorphous polyamide (component (B)):

(3) TABLE-US-00004 (AP1) nylon-6I/6T (Grivory G16, EMS), with a molar ratio 6I:6T of 1.9:1 Amorphous polymer (component (C)):

(4) TABLE-US-00005 (HP1) polysulfone (Ultrason S2010, BASF SE) (HP2) styrene-N-phenylmaleimide-maleic anhydride copolymer (Denka IP MS-NB, Denka) Additive:

(5) TABLE-US-00006 (A1) Irganox 1098 (N,N-hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4- hydroxyphenylpropionamide)), BASF SE) (A2) polyhydroxy ether-thermoplastic-thermoset resin (Phenoxy Resin, InChem)

(6) Table 1 states the essential parameters of the semicrystalline polyamides used (component (A)), table 2 states essential parameters of the amorphous polyamides used (component (B)), and tables 3 states essential parameters of the amorphous polymers used (component (C)).

(7) TABLE-US-00007 TABLE 1 Zero shear rate viscosity AEG CEG T.sub.M T.sub.G .sub.0 at 240 C. Type [mmol/kg] [mmol/kg] [ C.] [ C.] [Pas] P1 PA 6 36 54 220.0 53 399

(8) TABLE-US-00008 TABLE 2 Zero shear rate viscosity AEG CEG T.sub.G .sub.0 at 240 C. Type [mmol/kg] [mmol/kg] [ C.] [Pas] AP1 PA 6I/6T 37 86 125 770

(9) TABLE-US-00009 TABLE 3 Viscosity Melt volume T.sub.G Density number VN flow rate MVR Type [ C.] [g/cm.sup.3] [ml/g] [g/10 min] HP1 Polysulfone 185 1.234 63 90 (360 C., 10 kg) HP2 Styrene-N- 196 1.18 3 phenylmale- (265 C., 10 kg) imide-maleic anhydride copolymer

(10) AEG indicates the amino end group concentration. This is determined by means of titration. For determination of the amino end group concentration (AEG), 1 g of the component (semicrystalline polyamide or amorphous polyamide) was dissolved in 30 mL of a phenol/methanol mixture (volume ratio of phenol:methanol 75:25) and then subjected to potentiometric titration with 0.2 N hydrochloric acid in water.

(11) The CEG indicates the carboxyl end group concentration. This is determined by means of titration. For determination of the carboxyl end group concentration (CEG), 1 g of the component (semicrystalline polyamide or amorphous polyamide) was dissolved in 30 mL of benzyl alcohol. This was followed by visual titration at 120 C. with 0.05 N potassium hydroxide solution in water.

(12) The melting temperature (T.sub.M) of the semicrystalline polyamides and all glass transition temperatures (T.sub.G) were each determined by means of differential scanning calorimetry.

(13) For determination of the melting temperature (T.sub.M), as described above, a first heating run (H1) at a heating rate of 20 K/min was measured. The melting temperature (T.sub.M) then corresponded to the temperature at the maximum of the melting peak of the heating run (H1).

(14) For determination of the glass transition temperature (T.sub.G), after the first heating run (H1), a cooling run (C) and subsequently a second heating run (H2) were measured.

(15) The cooling run was measured at a cooling rate of 20 K/min; the first heating run (H1) and the second heating run (H2) were measured at a heating rate of 20 K/min. The glass transition temperature (T.sub.G) was then determined as described above at half the step height of the second heating run (H2).

(16) The zero shear rate viscosity no was determined with a DHR-1 rotary viscometer from TA Instruments and a plate-plate geometry with a diameter of 25 mm and a plate separation of 1 mm. Unequilibrated samples were dried at 80 C. under reduced pressure for 7 days and these were then analyzed with a time-dependent frequency sweep (sequence test) with an angular frequency range of 500 to 0.5 rad/s. The following further analysis parameters were used: deformation: 1.0%, analysis temperature; 240 C., analysis time: 20 min, preheating time after sample preparation: 1.5 min.

(17) Density was determined to DIN EN ISO 1183-1:2013.

(18) The melt volume flow rate (MVR) was determined to DIN EN ISO 1133-1:2011.

(19) Viscosity number was determined to ISO 307, 1157, 1628.

(20) Blends Comprising a Single Amorphous Polymer

(21) For production of blends, the components specified in table 4 were compounded in the ratios specified in table 4 in a DSM 15 cm.sup.3 miniextruder (DSM-Micro15 microcompounder) at a speed of 80 rpm (revolutions per minute) at 260 C. for a mixing time of 3 min (minutes) and then extruded. The extrudates obtained were then ground in a mill and sieved to a particle size of <200 m.

(22) The blends obtained were characterized. The results can be seen in table 5.

(23) TABLE-US-00010 TABLE 4 (P1) (AP1) (HP1) (A1) (A2) (A3) [% [% [% [% [% [% Example by wt.] by wt.] by wt.] by wt.] by wt.] by wt.] C1 100 C2 79 21 C3 78.6 21 0.4 I4 79.6 18 0.4 2

(24) TABLE-US-00011 TABLE 5 Magnitude Ratio of of complex viscosity Sintering viscosity at after window 0.5 rad/s, aging to Sintering W after Exam- 240 C. before T.sub.M T.sub.C window aging ple [Pas] aging [ C.] [ C.] W [C] [C] C1 370 0.11 219.7 187.8 16.7 11.2 C2 483 0.39 219.5 173.2 24.5 23.9 C3 569 5.75 217.7 175.8 25.8 27.9 I4 740 1.18 219.1 187.3 18.1 15.3

(25) The melting temperature (T.sub.M) was determined as described above.

(26) The crystallization temperature (T.sub.C) was determined by means of differential scanning calorimetry. For this purpose, first a heating run (H) at a heating rate of 20 K/min and then a cooling run (C) at a cooling rate of 20 K/min were measured. The crystallization temperature (T.sub.C) is the temperature at the extreme of the crystallization peak.

(27) The magnitude of the complex shear viscosity was determined by means of a plate-plate rotary rheometer at an angular frequency of 0.5 rad/s and a temperature of 240 C. A DHR-1 rotary viscometer from TA Instruments was used, with a diameter of 25 mm and a plate separation of 1 mm. Unequilibrated samples were dried at 80 C. under reduced pressure for 7 days and these are then analyzed with a time-dependent frequency sweep (sequence test) with an angular frequency range of 500 to 0.5 rad/s.

(28) The following further analysis parameters were used: deformation: 1.0%, analysis time: 20 min, preheating time after sample preparation: 1.5 min.

(29) The sintering window (W) was determined, as described above, as the difference between the onset temperature of melting (T.sub.M.sup.onset) and the onset temperature of crystallization (T.sub.C.sup.onset).

(30) To determine the thermooxidative stability of the blends, the complex shear viscosity of freshly produced blends and of blends after oven aging at 0.5% oxygen and 195 C. for 16 hours was determined. The ratio of viscosity after storage (after aging) to the viscosity before storage (before aging) was determined. The viscosity is measured by means of rotary rheology at a measurement frequency of 0.5 rad/s at a temperature of 240 C.

(31) It can be seen from the examples in table 5 that the use of inventive components (A), (B) and (C) in the blend achieves improved thermal stability over the pure component (A). In addition, a broadened sintering window is achieved, especially after thermal storage.

(32) Sinter Powder for Selective Laser Sintering

(33) For production of sinter powders, the components specified in table 6 were compounded in the ratio specified in table 6 in a twin-screw extruder (MC26) at a speed of 300 rpm (revolutions per minute) and a throughput of 10 kg/h at a temperature of 270 C. with subsequent extrudate pelletization. The pelletized material thus obtained was ground to a particle size of 20 to 100 m.

(34) The sinter powders obtained were characterized as described above. The results can be seen in table 7.

(35) TABLE-US-00012 TABLE 6 (P1) (AP1) (HP1) (HP2) (A1) (A2) [% [% [% [% [% [% Example by wt.] by wt.] by wt.] by wt.] by wt.] by wt.] C5 100 C6 79 21 C7 78.5 21 0.5 I8 58.5 21 18 0.5 2 C9 58.5 21 20 0.5 I10 60.5 21 18 0.5

(36) TABLE-US-00013 TABLE 7 Broadening of Broadening of Magnitude of Ratio of sintering sintering complex viscosity viscosity after Sintering window W window W at 0.5 rad/s, aging to T.sub.M T.sub.C T.sub.G Sintering window W after compared to (C8) compared to (C8) Example 240 C. [Pas] before aging [ C.] [ C.] [ C.] window W [C] aging [C] [C] after aging [C] C5 370 0.11 219.7 187.8 53 16.7 11.2 C6 637 0.25 217.9 173.4 66 24.1 23.9 C7 692 2.92 217.8 170.2 66 28.2 26.8 I8 1362 1.47 215.0 167 73 28.8 31.4 0.6 4.6 C9 1551 1.21 215.7 166.7 70 29.4 31.5 1.2 4.7 I10 1302 1.08 216.4 168.0 71 27.7 28.9 0.5 2.1

(37) The sinter powders from inventive examples 18 and 110 and from comparative example C9 exhibit a distinctly broadened sintering window after aging. There is likewise a distinct improvement in the aging stability, characterized by the viscosity ratio after aging to before aging, over comparative examples C5, C6 and C7. As shown further down, the elongation at break properties of shaped bodies produced from the sinter powder according to comparative example C9, however, are much poorer than those of the shaped bodies produced from the inventive sinter powders according to examples I8 and I10.

(38) Laser Sintering Experiments

(39) The sinter powder was introduced with a layer thickness of 0.12 mm into the cavity at the temperature specified in table 8. The sinter powder was subsequently exposed to a laser with the laser power output specified in table 8 and the point spacing specified, with a speed of the laser over the sample during exposure of 5 m/s. The point spacing is also known as laser spacing or lane spacing. Selective laser sintering typically involves scanning in stripes. The point spacing gives the distance between the centers of the stripes, i.e. between the two centers of the laser beam for two stripes.

(40) TABLE-US-00014 TABLE 8 Temperature Laser power Laser speed Point spacing Example [ C.] output [W] [m/s] [mm] C5 209 18 5 0.2 C6 195 20 5 0.2 C7 200 25 5 0.2 I8 195 25 5 0.2 C9 195 25 5 0.2 I10 198 25 5 0.2

(41) Subsequently, the properties of the tensile bars (sinter bars) obtained were determined. The tensile bars (sinter bars) obtained were tested in the dry state after drying at 80 C. for 336 h under reduced pressure. The results are shown in table 9. In addition, Charpy bars were produced, which were likewise tested in dry form (according to ISO179-2/1 eU: 1997+Amd.1:2011).

(42) The warpage of the sinter bars obtained was determined by placing the sinter bar with the concave side down onto a planar surface. The distance (a.sub.m) between the planar surface and the upper edge of the middle of the sinter bar was then determined. In addition, the thickness (d.sub.m) in the middle of the sinter bar was determined. Warpage in % is then determined by the following formula:
V=100.Math.(a.sub.md.sub.m)/d.sub.m

(43) The dimensions of the sinter bars were typically length 80 mm, width 10 mm and thickness 4 mm.

(44) The flexural strength corresponds to the maximum stress in the bending test. The bending test is a three-point bending test according to EN ISO 178:2010+A1:2013.

(45) Processability was assessed quantitatively with 2 meaning good, i.e. low warpage of the component, and 5 meaning inadequate, i.e. severe warpage of the component.

(46) Tensile strength, tensile modulus of elasticity and elongation at break were determined according to ISO 527-1:2012.

(47) The water absorption of the tensile bars (sinter bars) obtained was determined by weighing the tensile bars in the dried state (after storage at 80 C. under reduced pressure for 336 hours) and in the conditioned state (after storage at 70 C. and 62% relative humidity for 336 hours).

(48) TABLE-US-00015 TABLE 9 Charpy Charpy Warpage Tensile impact notch of flexural Flexural Tensile modulus Elongation resistance impact Water bar from Processibility strength strength of elasticity at break a.sub.CU strength absorption Example SLS [%] in SLS [MPa] [MPa] [MPa] [%] [kJ/m.sup.2] [kJ/m.sup.2] [% by wt.] C5 45-55 4 C6 not 2 determined C7 52 14 2 100 64 3600 1.9 5.0 1.5 2.7 I8 32 7 1 95 76 3300 2.8 7.6 1.65 1.9 C9 30 3 1 43 28.5 3100 0.9 I10 0.4 1.2 1 68.9 3500 2.5 8.1

(49) It is apparent that a shaped body produced with the sinter powder according to comparative example C9 does have low warpage, but also exhibits only very low elongation at break.

(50) The shaped bodies produced from the inventive sinter powders according to examples I8 and I10 have reduced warpage together with elevated elongation at break and impact resistance.

(51) It is apparent that shaped bodies produced with the sinter powder (SP) of the invention give a lower water absorption of only 1.9% by weight. The theoretical expectation was 2.16% by weight, the theoretical calculation being based on the assumption that, when the sinter powder (SP) comprises 20% by weight of polyamides of various components that do not absorb water, the sinter powder exhibits 80% of the water absorption of a sinter powder comprising exclusively polyamide (C7).