Sinter powder containing a mineral flame retardant for producing moulded bodies

Abstract

The present invention relates to a process for producing a shaped body, wherein, in step i), a layer of a sinter powder (SP) comprising at least one mineral flame retardant inter alia is provided and, in step ii), the layer provided in step i) is exposed. The present invention further relates to a process for producing a sinter powder (SP) and to a sinter powder (SP) obtainable by this process. The present invention also relates to the use of the sinter powder (SP) in a sintering process and to shaped bodies obtainable by the process of the invention.

Claims

1. A process for producing a shaped body, comprising the steps of: i) providing a layer of a sinter powder (SP) comprising the following components: (A) at least one semicrystalline polyamide, (B) at least one amorphous polyamide, (C) at least one mineral flame retardant, ii) exposing the layer of the sinter powder (SP) provided in step i), wherein the sinter powder (SP) comprises in the range from 30% to 70% by weight of component (A), in the range from 5% to 25% by weight of component (B) and in the range from 20% to 60% by weight of component (C), based in each case on the total weight of the sinter powder (SP); wherein component (C) in the sinter powder (SP) has been coated with component (A) and/or with component (B).

2. The process according to claim 1, wherein component (C) is based on magnesium and/or aluminum.

3. The process according to claim 1, wherein component (C) is selected from the group consisting of magnesium hydroxide, aluminum oxide hydroxide and aluminum hydroxide.

4. The process according to claim 1, wherein the exposing in step ii) is effected with a radiation source selected from the group consisting of lasers and infrared sources.

5. The process according to claim 1, wherein component (A) is selected from the group consisting of PA 4, PA 6, PA 7, PA 8, PA 9, PA 11, PA 12, PA 46, PA 66, PA 69, PA 6.10, PA 6.12, PA 6.13, PA 6/6.36, PA6T/6, PA 12.12, PA 13.13, PA 6T, PA MXD6, PA 6/66, PA 6/12 and copolyamides of these.

6. The process according to claim 1, wherein component (B) is selected from the group consisting of PA 6I/6T, PA 6I and PA 6/3T.

7. The process according to claim 1, wherein the sinter powder (SP) additionally comprises in the range from 0.1% to 10% by weight of at least one additive selected from the group consisting of antinucleating agents, stabilizers, end group functionalizers, dyes and color pigments, based on the total weight of the sinter powder (SP).

8. The process according to claim 1, wherein the sinter powder (SP) has a D10 in the range from 10 to 60 μm, a D50 in the range from 25 to 90 μm and a D90 in the range from 50 to 150 μm, wherein the D10, D50 and D90 values are determined by means of laser diffraction using a Mastersizer 3000 by Malvern.

Description

EXAMPLES

(1) The following components are used: semicrystalline polyamide (component (A)): (P1) nylon-6 (Ultramid B27, BASF SE) (P2) nylon-6/6,6 (Ultramid C33, BASF SE) amorphous polyamide (component (B)): (AP1) nylon-6I/6T (Grivory G16, EMS), with a molar ratio of 6I:6T of 1.9:1 (AP2) nylon-6/3T (Trogamid T 5000, Evonik) mineral flame retardant (component (C)): (FM1) magnesium hydroxide (Magnifin H5 IV, Albemarle), aminosilane-modified, bulk density 501 kg/m.sup.3, particle size distribution D10=0.8 μm, D50=1.7 μm, D90=3.1 μm, determined by means of laser scattering Additive: (A1) phenolic antioxidant (Irganox 1098 (N,N′-hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide))), BASF SE) (A2) carbon black in the form of batch UB420 (30% in PA 6), (Special black 4, CAS No. 1333-86-4, Evonik)

(2) Table 1 states the essential parameters of the semicrystalline polyamides used (component (A)).

(3) Table 2 the essential parameters of the amorphous polyamides used (component (B)).

(4) TABLE-US-00003 TABLE 1 Zero-shear viscosity η.sub.0 at AEG CEG T.sub.M T.sub.G 240° C. Type [mmol/kg] [mmol/kg] [° C.] [° C.] [Pas] P1 PA 6 36 54 220.0 53 399 P2 PA 6/66 47 40 193.7 50 2300

(5) TABLE-US-00004 TABLE 2 Zero-shear viscosity η.sub.0 at AEG CEG 240° C. Type [mmol/kg] [mmol/kg] T.sub.g, [° C.] [Pas] AP1 PA 6I6T 37 86 125 770 AP2 PA 6/3T 45 59 150 7200 at 0.5 rad/s

(6) 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) is dissolved in 30 mL of a phenol/methanol mixture (volume ratio of phenol:methanol 75:25) and then subjected to visual titration with 0.2N hydrochloric acid in water.

(7) 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) is dissolved in 30 mL of benzyl alcohol and then subjected to visual titration at 120° C. with 0.05 N potassium hydroxide solution in water.

(8) 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.

(9) 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 first heating run (H1).

(10) 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. 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 at half the step height of the second heating run (H2).

(11) 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.

(12) Production of Sinter Powders in a Twin-Screw Extruder

(13) For production of sinter powders, the components specified in table 3 were compounded in the ratio specified in table 3 in a twin-screw extruder (ZE25) at a speed of 230 rpm (revolutions per minute) at 270° C. at a throughput of 20 kg/h, pelletized, and then processed with a liquid nitrogen-cooled pinned-disk mill to give powders (particle size distribution 10 to 100 μm).

(14) TABLE-US-00005 TABLE 3 (P1) (P2) (AP1) (AP2) (FM1) (A1) (A2) Example [% by wt.] [% by wt.] [% by wt.] [% by wt.] [% by wt.] [% by wt.] [% by wt.] V1 78.6 21 0.4 B2 66.8 17.8 15 0.4 B3 62.8 16.8 20 0.4 V4 79.6 20 0.4 B4a 64.36 10.0 25 0.4 0.25 B4b 64.25 10.5 25 0.25 B5 56.5 15.1 28 0.4 B6 56.17 15.1 28 0.4 0.33 B7 56.17 15.1 28 0.4 0.33 B8 51.0 13.6 35 0.4 B9 55.65 9.1 35 0.25 B10 39.1 10.5 50 0.4

(15) For the powders, the melting temperature (T.sub.M) was determined as described above.

(16) The crystallization temperature (T.sub.C) was determined by means of differential scanning calorimetry (DSC). 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.

(17) 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 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 time: 20 min, preheating time after sample preparation: 1.5 min.

(18) 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).

(19) To determine the thermooxidative stability of the sinter powders, the complex shear viscosity of freshly produced sinter powders and of sinter powders 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.

(20) The viscosity is measured by means of rotary rheology at a measurement frequency of 0.5 rad/s at a temperature of 240° C.

(21) The results can be seen in table 4.

(22) TABLE-US-00006 TABLE 4 Magnitude of complex Ratio of viscosity Sintering viscosity at 0.5 after aging to Sintering window W Example rad/s, 240° C. [Pas] before aging T.sub.M [° C.] T.sub.C [° C.] window W[K] after aging [K] V1 632 3.4 218.2 172.5 28.3 27.1 B2 1030 0.98 217.6 173.8 24.4 24.0 B3 1350 1.24 217.9 174.9 26.1 25.9 V4 1140 0.95 219.1 183.7 21.6 17.5 B4a 1380 1.26 217.8 178.8 22.1 n.d. B4b 6250 3.8 193.0 143.2 29.6 n.d. B5 1646 1.2 217.6 173.8 26.4 n.d. B6 1630 1.2 217.2 173.0 26.3 25.7 B7 2910 1.05 218.2 176.0 25.3 21.1 B8 2646 1.5 217.3 173.3 24.6 n.d. B9 9300 5.5 192.5 143.9 29.0 40.1 B10 6100 5.3 217.1 172.6 27.9 n.d. n.d.: not determined

(23) It is apparent that the sinter powders of the invention have a sintering window sufficient for selective laser sintering, even after aging.

(24) In addition, for the sinter powders obtained, bulk density is determined to DIN EN ISO 60 and tamped density to DIN EN ISO 787-11, as is the Hausner factor as the ratio of tamped density to bulk density.

(25) Particle size distribution, reported as the D10, D50 and D90 value, was determined as described above with a Malvern Mastersizer.

(26) Magnesium content was determined by means of atomic spectroscopy.

(27) The avalanche angle was determined by means of a Revolution Powder Analyzer (RPA) with a rotation speed of 0.6 rpm and 15 images per second. The average was found from 128 avalanche events.

(28) The results can be seen in table 5.

(29) TABLE-US-00007 TABLE 5 Bulk density Tamped density Hausner D10 D50 D90 Avalanche Mg content Examples [kg/m.sup.3] [kg/m.sup.3] factor [μm] [μm] [μm] angle [°] [g/100 g] V1 460 570 1.24 39 65 107 52   0   B2 499 600 1.20 42 66.5 104 n.d. n.d. B3 532 642 1.21 37 63.5 104 n.d. 8.5 V4 n.d. n.d. n.d. 38 65.5 108 n.d. n.d. B4a n.d. n.d. n.d. 39.2 65.3 106 n.d. n.d. B4b 520 634 1.22 39 65.8 108 n.d. n.d. B5 n.d. n.d. n.d. 35 63.5 108 45.9 n.d. B6 n.d. n.d. n.d. 48.5 75.7 117 51.1 n.d. B7 n.d. n.d. n.d. 43 67.4 104 n.d. n.d. B8 n.d. n.d. n.d. 38 63 103 n.d. n.d. B9 553 684 1.24 37.6 64.5 107 n.d. n.d. B10 n.d. n.d. n.d. 40 66 107 n.d. n.d. n.d.: not determined

(30) Laser Sintering Experiments

(31) The sinter powders (SP) were introduced with a layer thickness of 0.1 mm into the cavity at the temperature specified in table 6. The sinter powders were subsequently exposed to a laser with the laser power output specified in table 6 and the point spacing specified, with a speed of the laser over the sample during exposure of 15 m/sec. 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. The laser sintering experiments were done on Farsoon HT251.

(32) TABLE-US-00008 TABLE 6 Construction space temperature Laser power Laser Point Example [° C.] output [W] speed [m/s] spacing [mm] V1 198 25 5 0.2 B2 206 55 15 0.2 B3 205 32 5 0.2 V4 203 68 12.5 0.2 B4a 207 50 15 0.2 B4b 184 50 15 0.2 B5 208 55 15 0.2 B6 202 55 15 0.2 B7 204 55 15 0.2 B8 200 32 5 0.2 B9 190 55 15 0.2 B10 206 30 5 0.2

(33) The flame retardancy properties of the laser-sintered test specimens were determined to UL 94 Vx: 2016 (vertical test). The determination was effected firstly after storage at 23° C. and 50% relative humidity for 2 days and secondly after storage at 70° C. in a drying cabinet for 7 days.

(34) The results and the thickness of the test specimens are shown in table 7.

(35) TABLE-US-00009 TABLE 7 Thickness of UL test 2 days/23° C./ Example specimen [mm] 50% r.h. 7 days/70° C. V1 0.8 V-- V-- 1.7 V-- V-- B2 0.96 V-- V-- 1.6 V-- V-- B3 1.25-1.4 V-2, 41 s V-2, 40 s 0.85 V-2, 20 s V-2, 17 s 0.94 V-2, 66 s n.d. 1.5 V-2, 44 s V-2, 48 s 2.2 V-2, 51 s V-2, 69 s V4 0.84 V-2, 15 s V-2, 69 s 1.7 V-2, 49 s V-2, 73 s B4a 0.52 V-2, 14 s V-2, 9 s 0.84 V-2, 9 s V-2, 21 s 1.7 V-2, 60 s V-2, 68 s B4b 0.82 V-2, 16 s V-2, 6 s 1.56 V-2 38 s V-2, 31 s B5 1.0 n.d. V-2, 33 s 1.8 n.d. V-2, 79 s B6 0.81 V-2, 13 s V-2, 11 s 1.6 V-2, 44 s V-2, 46 s B7 0.88 V-2, 12 s V-2, 19 s 1.6 V-2, 47 s V-2, 57 s B8 0.84 V-2, 17 s n.d. 1.8 V-2, 54 s n.d. B9 0.95 V-2, 19 s V-2, 13 s 1.7 V-2, 48 s V-2, 42 s B10 1.0 V-2, 21 s n.d. 1.9 V-2, 19 s n.d. n.d.: not determined

(36) Subsequently, the properties of the tensile bars (sinter bars) obtained were additionally determined. The tensile bars (sinter bars) obtained were tested in the dry state after drying at 80° C. for 336 hours under reduced pressure. The results are shown in table 8. Charpy specimens were also produced, which were likewise tested in dry form (to ISO 179-2/1 eA(F): 1997+ Amd. 1: 2011 and to ISO 179-2/1 eU: 1997+ Amd. 1: 2011).

(37) Tensile strength, tensile modulus of elasticity and elongation at break were determined to ISO 527-2: 2012.

(38) Heat deflection temperature (HDT) was determined according to ISO 75-2: 2013, using both Method A with an edge fiber stress of 1.8 N/mm.sup.2 and Method B with an edge fiber stress of 0.45 N/mm.sup.2.

(39) The results can be seen in table 8.

(40) TABLE-US-00010 TABLE 8 Charpy Charpy impact impact Tensile resistance resistance Tensile modulus of Elongation unnotched notched strength elasticity at break HDT A HDT B Example [kJ/m.sup.2] [kJ/m.sup.2] [MPa] [MPa] [%] [° C.] [° C.] V1  4.94 1.5   56.7 3660 1.7   94.4   150.4 B2 n.d. n.d. n.d. n.d. n.d. n.d. n.d. B3 7.3 2.9 61 4390 1.6 114 210 V4 8.2 2.3 62 4370 1.8 n.d. n.d. B4a 7.0 1.5 63 5170 1.4 n.d. n.d. B4b n.d. n.d. 54 3610 1.9 n.d. n.d. B5 8.1 1.4 64 5230 1.4 116 203 B6 n.d. n.d. 49 5560 1.6 123 203 B7 n.d. n.d. 57 4780 1.4 n.d. n.d. B8 n.d. n.d. n.d. n.d. n.d. n.d. n.d. B9 n.d. n.d. 41 3680 1.5 n.d. n.d. B10 5.0 2.0 53 7090 0.8 126 204 n.d.: not determined

(41) The sinter powders of the invention show good SLS processability and low warpage.