SINTER POWDER (SP) CONTAINING A SEMI-CRYSTALLINE TEREPHTHALATE POLYESTER

Abstract

The present invention relates to a sinter powder (SP) comprising at least one semicrystalline terephthalate polyester (A) which is prepared by reacting at least one aromatic dicarboxylic acid (a) and at least two aliphatic diols (b1) and (b2), where the aliphatic diol (b1) is neopentyl glycol. The present invention further relates to a method of producing the sinter powder (SP), and to a method of producing a shaped body by sintering the sinter powder (SP). The present invention further relates to the shaped body obtainable by the sintering. The present invention also relates to the use of the sinter powder (SP) in a sintering method.

Claims

1.-14. (canceled)

15. A sinter powder (SP) comprising the following components (A) and optionally (B), (C) and/or (D): (A) at least one semicrystalline terephthalate polyester which is prepared by reacting at least components (a) and (b): (a) at least one aromatic dicarboxylic acid and (b) at least two aliphatic diols (b1) and (b2), where the aliphatic diol (b1) is neopentyl glycol, (B) optionally at least one further polymer, (C) optionally at least one additive and/or (D) optionally at least one reinforcer, where the molar ratio of component (a) to component (b1) in the preparation of the at least one semicrystalline terephthalate polyester (A) is in the range from 1:0.15 to 1:0.65 [mol/mol] and the aliphatic diol (b2) is a linear diol of the general formula (I)
HO—(CH.sub.2).sub.n—OH  (I) in which n is 2, 3, 4, 5 or 6.

16. The sinter powder (SP) according to claim 15, wherein the molar ratio of component (a) to component (b) in the preparation of the at least one semicrystalline terephthalate polyester (A) is in the range from 1:0.8 to 1:1.1 [mol/mol].

17. The sinter powder (SP) according to claim 15, wherein the molar ratio of component (a) to component (b1) in the preparation of the at least one semicrystalline terephthalate polyester (A) is in the range from 1:0.2 to 1:0.5 [mol/mol].

18. The sinter powder (SP) according to claim 15, wherein component (a) is selected from the group consisting of terephthalic acid, isophthalic acid and phthalic acid.

19. The sinter powder (SP) according to claim 15, wherein the sinter powder (SP) has i. a median particle size (D50) in the range from 10 to 250 μm, and/or ii. 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, and/or iii. has been heat treated.

20. The sinter powder (SP) according to claim 15, wherein i) component (B) is a polymer selected from the group consisting of polyolefins, polyesters, polyamides, polycarbonates and polyacrylates, and/or ii) component (C) is selected from antinucleating agents, impact modifiers, flame retardants, stabilizers, conductive additives, end group functionalizers, dyes, antioxidants and color pigments, and/or iii) component (D) is selected from the group consisting of carbon nanotubes, carbon fibers, boron fibers, glass fibers, glass beads, silica fibers, ceramic fibers, basalt fibers, aluminum silicates, aramid fibers and polyester fibers.

21. The sinter powder (SP) according to claim 15, wherein the sinter powder (SP) has a melting temperature (T.sub.M) in the range from 130 to 210° C., where the melting temperature (T.sub.M) is determined by dynamic scanning calorimetry according to the description.

22. The sinter powder (SP) according to claim 15, wherein the sinter powder (SP) has a crystallization temperature (T.sub.C) in the range from 70 to 130° C., where the crystallization temperature (T.sub.M) is determined by dynamic scanning calorimetry according to the description.

23. The sinter powder according to claim 15, wherein the sinter powder (SP) has a first enthalpy of fusion ΔH1.sub.(SP) and a second enthalpy of fusion ΔH2.sub.(SP), where the difference between the first enthalpy of fusion ΔH1.sub.(SP) and the second enthalpy of fusion ΔH2.sub.(SP) is at least 10 J/g, where the first enthalpy of fusion ΔH1.sub.(SP) and the second enthalpy of fusion ΔH2.sub.(SP) are determined by dynamic scanning calorimetry according to the description.

24. A method of producing a sinter powder (SP) according to claim 15, comprising the steps of a) mixing components (A) and optionally (B), (C) and/or (D): (A) at least one semicrystalline terephthalate polyester which is prepared by reacting at least components (a) and (b): (a) at least one aromatic dicarboxylic acid and (b) at least two aliphatic diols (b1) and (b2), where the aliphatic diol (b1) is neopentyl glycol, (B) optionally at least one further polymer, (C) optionally at least one additive and/or (D) optionally at least one reinforcer, in an extruder to obtain an extrudate (E) comprising components (A) and optionally (B), (C) and/or (D), b) pelletizing the extrudate (E) obtained in step a) to obtain a pelletized material (G) comprising components (A) and optionally (B), (C) and/or (D), c) micronizing the pelletized material (G) obtained in step c) to obtain the sinter powder (SP).

25. The method according to claim 24, wherein the sinter powder (SP) obtained in step c) is then heat-treated in a step d) at a temperature T.sub.T to obtain a heat-treated sinter powder (SP).

26. A method of producing a shaped body, comprising the steps of: a) providing a layer of a sinter powder (SP) according to claim 15, b) optionally heating the layer up to a maximum of 2 K below the melting temperature T.sub.M of the sinter powder (SP), where the melting temperature T.sub.M is determined by means of dynamic scanning calorimetry according to the description, c) exposing the layer of the sinter powder (SP) provided in step a) or optionally heated in step b), preferably in a sintering method, more preferably in a selective laser sintering method, in a high-speed sintering (HSS) method or a multijet fusion (MJF) method.

27. A shaped body obtainable by a method according to claim 26.

28. The use of a sinter powder (SP) according to claim 15 in a sintering method, preferably in a selective laser sintering method, in a high-speed sintering (HSS) method or a multijet fusion (MJF) method.

Description

EXAMPLES

[0335] The following components are used:

[0336] Semicrystalline Terephthalate Polyester [0337] Component (A) in inventive examples E1, E2, E4, E5, E6 and E7 [0338] Advanite 53001 terephthalate polyester (pelletized material; Sasa Polyester Sanayi A.S., Turkey), prepared by reaction of components (a), (b1) and (b2): [0339] 52.4 mol % of terephthalic acid (component (a)), based on the total amount of components (a), (b1) and (b2), [0340] 12.2 mol % of neopentyl glycol (component (b1)), based on the total amount of components (a), (b1) and (b2), and [0341] 35.4 mol % of butanediol (component (b2)), based on the total amount of components (a), (b1) and (b2).

[0342] Semicrystalline Terephthalate Polyester in Comparative Example CE3 [0343] Ultradur B4500 polybutylene terephthalate (pelletized material; BASF SE), prepared by reaction of components (a) and (b2): [0344] 50 mol % of terephthalic acid or dimethyl terephthalate (corresponding to component (a)), based on the total amount of components (a) and (b2), and [0345] 50 mol % of butane-1,4-diol (corresponding to component (b2)), based on the total amount of components (a) and (b2).

[0346] Further Polymer (Component (8)) in Inventive Examples E6 and E7 [0347] Capa® 6500 polycaprolactone (pelletized material; Perstorp)

[0348] Additive (Component (C)) in Inventive Examples E6 and E7 [0349] Irganox® 245 antioxidant (BASF SE; sterically hindered phenol)

[0350] Reinforcer (Component (D)) in Inventive Examples E4 and E5 [0351] glass beads (Spheriglass® 2000 CP0202; Potters; B4) [0352] wollastonite (TREMIN® 939-300 EST; HPF; B5)

[0353] Flow Aid [0354] Aeroxide® Alu C (Evonik)

[0355] Test Methods:

[0356] The enthalpies of fusion ΔH1 and ΔH2, melting temperature (T.sub.M1) and glass transition temperature (T.sub.G2) were each determined by means of dynamic scanning calorimetry.

[0357] For determination of the melting temperature (T.sub.M1) and the first enthalpy of fusion ΔH1, as described above, a first heating run (H1) at a heating rate of 20 K/min was measured. For determination of the second enthalpy of fusion ΔH2, as described above, a second heating run (H2) at a heating rate of 20 K/min was measured. The melting temperature (T.sub.M1) then corresponded to the temperature at the maximum of the melting peak of the heating run (H1). The enthalpies of fusion ΔH1.sub.(SP) and ΔH2.sub.(SP) of the sinter powder (SP) are proportional to the area beneath the melting peak of the first heating (H1) and of the second heating run (H2) respectively in the DSC diagram.

[0358] For determination of the glass transition temperature (T.sub.G2), after the first heating run (H1), a cooling run (K) 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.G2) was then determined as described above at half the step height of the second heating run (H2).

[0359] 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.

[0360] Complex shear viscosity was determined using freshly produced sinter powders. Viscosity was measured here by means of rotary rheology at a measurement frequency of 0.5 rad/s at a temperature of 190° C. (E1, E2, E6 and E7) or 240° C. (CE3).

[0361] Production of the Sinter Powders

Inventive Examples E1, E2, E4 and E5 and Comparative Example CE3

[0362] The pelletized materials of the semicrystalline terephthalate polyesters were each ground while cooling with liquid nitrogen in a pinned disk mill to a particle size (D50) in the region of less than 150 μm to obtain a terephthalate polyester powder. The resultant terephthalate polyester powder was mixed with 0.2% by weight of flow aid, based on the total weight of the terephthalate polyester powder and the flow aid, or, based on the total weight of the sinter powder, to obtain the sinter powder (SP).

[0363] In inventive example E2, the resultant sinter powder (SP) was subsequently subjected to heat treatment at a temperature of 120° C. for 20 hours in a drying cabinet under reduced pressure to obtain a heat-treated sinter powder (SP). In inventive example E1, the sinter powder (SP) was not heat-treated. In inventive examples E4 and E5, after the sinter powder had been heat treated, a reinforcer (component (D)), glass beads (E4) and wollastonite (E5) were mixed in. The compositions of the sinter powders (SP) and of the heat-treated sinter powders (SP) are shown in tables 1 and 2; the physical properties of the sinter powders (SP) and of the heat-treated sinter powders (SP) are shown in tables 4 and 5.

Inventive Examples E6 and E7

[0364] The pellets of the semicrystalline terephthalate polyester (component (A)) and of the further polymer (component (B); polycaprolactone) and the antioxidant (component (C)) in the amounts specified in table 3 were mixed in an extruder to obtain an extrudate (E) and then pelletized to obtain a pelletized material (G). Subsequently, the pelletized material (G) was ground while cooling with liquid nitrogen in a pinned disk mill to a particle size (D50) in the region of less than 150 μm to obtain the sinter powder (SP). In inventive examples E6 and E7, the sinter powder (SP) was not heat-treated. The physical properties of the sinter powders (SP) are shown in tables 4 and 5.

TABLE-US-00001 TABLE 1 Example/ Terephthalate Component Component Component Comparative polyester powder (a) (b1) (b2) Flow aid example [% by wt]* [mol %]** [mol %]** [mol %]** [% by wt.]* E1 99.8 52.4 12.2 35.4 0.2 E2 99.8 52.4 12.2 35.4 0.2 CE3 99.8 50 — 50 0.2 *based on the tota weight of the sinter powder **based on the tota amount c of components (a), (b1) and (b2)

TABLE-US-00002 TABLE 2 Terephthalate Example/ polyester Component Component Component comparative powder (a) (b1) (b2) Flow aid Reinforcer example     [mol %]** [mol %]** [% by wt.]* [% by wt.]* [% by wt.]* E4 82.83 52.4 12.2 35.4 0.17 17 E5 82.83 52.4 12.2 35.4 0.17 17 *based on the tota weight of the sinter powder **based on the total amount of components (a), (b1) and (b2) indicates data missing or illegible when filed

TABLE-US-00003 TABLE 3 Component Component Example/ Component Component Component Component (B) (C) comparative (A) (a) (b1) (b2) [% by [% by example [% by wt.]* [mol %]** [mol %]** [mol %]** wt   ]* wt   ]* E6 97.25 52.4 12.2 35.4 2.5 0.25 E7 94.75 52.4 12.2 35.4 5.0 0.25 *based on the total weight of the sinter powder **based on the total amount of components (a), (b1) and (b2) indicates data missing or illegible when filed

TABLE-US-00004 TABLE 4 Example/ comparative D10 D50 D90 example [μm] [μm] [μm] E1 37 62 101 E2 37 62 101 CE3 30.7 61.5 115.6 E6 E7

TABLE-US-00005 TABLE 5 Complex shear Example/ viscosity comparative at 0.5 rad/ T.sub.M1 T.sub.G2 T.sub.C ΔH.sub.1 ΔH.sub.2 ΔH.sub.1 − ΔH.sub.2 example s [Pas] [° C.] [° C.] [° C.] [J/g] [J/g] [J/g] E1 1500 83.1 43.0 100.1 30 2 28 167.1 E2 1540 167.5 44.0 101.0 38 3 35 CE3 580 221.9 42.0 190.8 53 59 6 E4 — 167.1 44.0 103.0 31 4 27 E5 — 168.4 44.0 114.0 29 10 19 E6 315 168.0 42.0 100.6 32 17 15 E7 320 167.4 38.0 98.6 26 12 14

[0365] The sinter powders of inventive examples E1, E2, E3, E4, E5, E6 and E7 show a distinctly lower melting temperature (T.sub.M1) than the sinter powder of comparative example CE3, as a result of which the sinter powders of inventive examples E1, E2, E3, E4, E5, E6 and E7 can be used without difficulty in all standard laser sintering systems with maximum build space temperatures of 200° C. The sinter powders of inventive examples E1, E2, E3, E4, E5, E6 and E7 likewise feature very slow crystallization compared to the sinter powder of comparative example CE3, which shows the difference in the enthalpies of fusion from the first and second heating runs, and which achieves a distinctly broadened sintering window.

[0366] On comparison of examples E1 and E2, it is clear that an additional, low-lying fusion peak (83.1° C.) occurs in the case of E1. The effect of this is tackiness in the SLS process, which makes sinter powder E1 more difficult to process (see table 7). Heat treatment (example E2) leads to disappearance of this low-lying melting peak in the first heating run and to improved processibility.

[0367] This peak does not occur in inventive examples E6 and E7.

[0368] Laser Sintering Experiments

[0369] The sinter powder was introduced with a layer thickness of 0.1 mm into the cavity at the temperature specified in table 6. The sinter powder was 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/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.

TABLE-US-00006 TABLE 6 Example/ Laser power Laser Point comparative Temperature output speed spacing example [° C.] [W] [m/s] [mm] E1 140 50 15 0.18 E2 135-155 50 15 0.18 CE3 205-215 50 15 0.18 E4 140 50 15 0.18 E5 140 50 15 0.18

[0370] It is clear that the temperature with which the sinter powder of inventive examples E1 and E2 enters the build space, at 25° C. below the melting temperature, is very low compared to the temperature at which the sinter powder of comparative example CE3 was introduced into the build space.

[0371] 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 7. In addition, Charpy specimens were produced, which were likewise tested in dry form (according to ISO179-2/1eU: 1997+Amd.1:2011).

[0372] Processibility was assessed qualitatively with “2” meaning “good”, i.e. low warpage of the component, and “5” meaning “inadequate”, i.e. severe warpage of the component.

[0373] Tensile strength, tensile modulus of elasticity and elongation at break were determined according to ISO 527-1:2012.

TABLE-US-00007 TABLE 7 Charpy impact Example/ Tensile resistance, Charpy impact comparative Processibility Tensile modulus of Elongation at unnotched resistance, example in SLS strength [MPa] elasticity [MPa] break [%] [kJ/m.sup.2] notched [kJ/m.sup.2] E1 3 45 2300 2.5 n.d. n.d. E2 1 37-45 2300-2430 1.7-2.5 9-12 2.2 ± 0.2 CE3 6 n.d* n.d* n.d* n.d* n.d* E4 1 42 ± 1.3 2850 ± 45 1.7 ± 0.1  7.4 ± 0.6 1.6 ± 0.3 E5 1 45 ± 0.7 3740 ± 85 1.7 ± 0.1 13.1 ± 1.5 1.7 ± 0.2 *No mechanically testable components were obtained since warpage was too great

[0374] The shaped bodies produced from the inventive sinter powders according to examples E1, E2, E4 and E5 have reduced warpage together with a high tensile modulus of elasticity and high tensile strength. The mixing of a reinforcer (component (D)) into the sinter powder (SP) (E4 and E5) can achieve a further increase in tensile modulus of elasticity and tensile strength.