SINTER POWDER (SP) CONTAINING A THERMOPLASTIC POLYURETHANE, A PLASTICIZER AND AN ORGANIC ADDITIVE

Abstract

The present invention relates to a sinter powder (SP) comprising 59.5% to 99.85% by weight of at least one thermoplastic polyurethane (A), 0.05% to 0.5% by weight of at least one flow agent (B), 0.1% to 5% by weight of at least one organic additive (C), 0% to 5% by weight of at least one further additive (D) and 0% to 30% by weight of at least one reinforcer (E), based in each case on the sum total of the percentages by weight (A), (B), (C), (D) and (E). The present invention further relates to a method of producing a shaped body by sintering the sinter powder (SP), to a shaped body obtainable by the method of the invention, and to the use of at least one flow agent (B) and at least one organic additive (C) in a sinter powder (SP) to improve the flowability and coalescence of the sinter powder (SP). The present invention further relates to the use of the sinter powder (SP) in a sintering method, and to a method of producing the sinter powder (SP).

Claims

1.-14. (canceled)

15. A sinter powder (SP) comprising the following components: 59.5% to 99.85% by weight, based on the sum total of the percentages by weight of (A), (B), (C), (D) and (E), of at least one thermoplastic polyurethane (A), 0.05% to 0.5% by weight, based on the sum total of the percentages by weight of (A), (B), (C), (D) and (E), of at least one flow agent (B), 0.1% to 5% by weight, based on the sum total of the percentages by weight of (A), (B), (C), (D) and (E), of at least one organic additive (C), 0% to 5% by weight, based on the sum total of the percentages by weight of (A), (B), (C), (D) and (E), of at least one further additive (D) and 0% to 30% by weight, based on the sum total of the percentages by weight of (A), (B), (C), (D) and (E), of at least one reinforcer (E), wherein the at least one organic additive (C) is selected from the group consisting of maleic acid-polypropylene waxes, maleic anhydride-grafted polypropylene waxes, and amide waxes.

16. The sinter powder (SP) according to claim 15, wherein the at least one flow agent (B) is selected from the group consisting of silicon dioxide, silicates, silicas, metal oxides, minerals, borates, phosphates, sulfates and carbonates.

17. The sinter powder (SP) according to claim 15, wherein the sinter powder (SP) comprises i) 74.15% to 99.7% by weight, of component (A), based in each case on the sum total of the percentages by weight of (A), (B), (C), (D) and (E), and/or ii) 0.1% to 0.35% by weight, of component (B), based in each case on the sum total of the percentages by weight of (A), (B), (C), (D) and (E), and/or iii) 0.2% to 3% by weight, of component (C), based in each case on the sum total of the percentages by weight of (A), (B), (C), (D) and (E), and/or iv) 0% to 2.5% by weight of component (D), based on the sum total of the percentages by weight of (A), (B), (C), (D) and (E), and/or v) 0% to 20% by weight of component (E), based on the sum total of the percentages by weight of components (A), (B), (C), (D) and (E).

18. The sinter powder (SP) according to claim 15, wherein the at least one organic additive (C) i) is an N,N′-alkylene fatty acid diamide, and/or ii) is selected in such a way that the dropping point of the at least one organic additive (C) satisfies the following condition (formula I):
(T.sub.M(A)−25° C.)≤D.sub.P<(T.sub.M(A)+25° C.)  (I), where D.sub.P is the dropping point of the at least one organic additive (C) and T.sub.M(A) is the melting temperature of the at least one thermoplastic polyurethane (A), and/or iii) is selected such that the total interfacial energy γ.sub.S of the sinter powder (SP) is ≤25 mN.Math.m.sup.−1, and/or iv) is selected such that the disperse component of the interfacial energy γ.sub.S.sup.D of the sinter powder (SP) is ≤20 mN.Math.m.sup.−1, and/or v) is selected such that the polar component of the interfacial energy γ.sub.S.sup.P of the sinter powder (SP) is ≤5 mN.Math.m.sup.−1.

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 190 μm, and/or ii) a melting temperature (T.sub.M(SP)) in the range from 80 to 220° C., and/or iii) a melt volume flow rate (MVR) in the range from 3 to 150 cm.sup.3/10 min, and/or iv) a bulk density of ≥300 g/L.

20. The sinter powder (SP) according to claim 15, wherein the at least one flow agent (B) has a D90 of ≤10 μm.

21. The sinter powder (SP) according to claim 15, wherein the at least one further additive (D) is selected from the group consisting of antinucleating agents, stabilizers, conductive additives, end group functionalizers, dyes, antioxidants, flame retardants and color pigments.

22. The sinter powder (SP) according to claim 15, wherein the at least one reinforcer (E) is selected from the group consisting of carbon nanotubes, glass beads and aluminum silicates.

23. A method of producing a sinter powder (SP) comprising 59.5% to 99.85% by weight, based on the total weight of the sinter powder (SP), of at least one thermoplastic polyurethane (A), 0.05% to 0.5% by weight, based on the total weight of the sinter powder (SP), of at least one flow agent (B), 0.1% to 5% by weight, based on the total weight of the sinter powder (SP), of at least one organic additive (C), 0% to 5% by weight, based on the total weight of the sinter powder (SP), of at least one further additive (D) and 0% to 30% by weight, based on the total weight of the sinter powder (SP), of at least one reinforcer (E), comprising the step of a) grinding the total amount, based on the total weight of the sinter powder (SP), of component (A), wherein a first portion (BT1) of the total amount, based on the total weight of the sinter powder (SP), of component (B) and/or a first portion (CT1) of the total amount, based on the total weight of the sinter powder (SP), of component (C) are mixed into component (A) prior to step a) to obtain a powder (P), and the remaining portion (BT2) of the total amount of component (B) and/or the remaining portion (CT2) of the total amount of component (C) are mixed into the powder (P) after step a) to obtain the sinter powder (SP), wherein the first portion (BT1) accounts for 0% to 100% by weight of the total amount, based on the total weight of the sinter powder (SP), of component (B) and wherein the first portion (CT1) accounts for 0% to 100% of the total amount, based on the total weight of the sinter powder (SP), of component (C), and wherein the remaining portion (BT2) accounts for (100−BT1)% by weight of the total amount, based on the total weight of the sinter powder (SP), of component (B) and the remaining portion (CT2) accounts for (100−CT1)% by weight of the total amount, based on the total weight of the sinter powder (SP), of component (C), and wherein optionally the total amount, based on the total weight of the sinter powder (SP), of component (D) and/or the total amount, based on the total weight of the sinter powder (SP), of component (E) is mixed in before step a) or after step a), wherein the at least one organic additive (C) is selected from the group consisting of maleic acid- and/or maleic anhydride-grafted polypropylene waxes and amide waxes.

24. A method of producing a shaped body, comprising the steps of: i) providing a layer of a sinter powder (SP) according to claim 15, and ii) exposing or heating the layer of the sinter powder (SP) provided in step i).

25. A shaped body obtained by a method according to claim 24.

26. The use of at least one flow agent (B) and at least one organic additive (C) in a sinter powder (SP) comprising at least one thermoplastic polyurethane (A) for improving the flowability and coalescence of the sinter powder (SP), wherein the at least one organic additive (C) is selected from the group consisting of maleic acid- and/or maleic anhydride-grafted polypropylene waxes and amide waxes.

27. A method comprising utilizing the sinter powder (SP) according to claim 15 in a sintering method.

28. A shaped body obtained via a sintering method using the sinter powder (SP) according to claim 15.

Description

EXAMPLES

[0311] The following components are used: [0312] Component (A): thermoplastic polyurethane (TPU); Elastollan SP9415, BASF SE [0313] Component (B1): hydrophobic fumed silica; Aerosil R 812, Evonik, Germany [0314] Component (B2): hydrophobic fumed silica; HDK H20, Wacker Chemie [0315] Component (B3): hydrophobic fumed silica; Aerosil R 972, Evonik, Germany [0316] Component (C): N,N′-ethylenedi(stearamide), dropping point D.sub.P=142° C.

[0317] Test Methods:

[0318] Determination of the Interfacial Energy of the Sinter Powder (SP)

[0319] The interfacial energy of the sinter powder (SP) was calculated with the aid of the Owens-Wendt model (Owens, D. K.; Wendt, R. C.; Journal of Applied Polymer Science, 13, 1741, (1969)).

[0320] For this purpose, the pulverulent samples were applied to a self-produced adhesive film (Acronal V215 on PET film). Excess material was removed with an air gun. 8 to 10 drops of the test liquids described in table 1 were each applied to the powder layers with a droplet volume of about 1.5 μL. The contact angle θ was determined by droplet contour analysis directly after the first contact with the surface (5 s after the separation of the droplet). The measurement was conducted at 23° C. The analysis unit used was a Drop Shape Analyzer DSA100 (Kruss GmbH, Germany).

[0321] FIG. 2 shows the contact angle θ, the interfacial energy of the test liquid γ.sub.L, the interfacial energy of the sinter powder (SP) γ.sub.S and the interfacial energy γ.sub.SL between test liquid and sinter powder (SP). The contact angle is measured by applying the test liquid (I) to the sample (II).

TABLE-US-00001 TABLE 1 Interfacial energy (mN m.sup.−1) Disperse Polar component component Total (γ.sub.L.sup.D) (γ.sub.L.sup.P) (γ.sub.L) Ethylene glycol 26.4 21.3 47.7 Formamide 39.5 18.7 58.2 Water 21.8 51.0 72.8

[0322] With the aid of the Owens-Wendt equation (formula IX) and the measured contact angle θ, it is possible by means of linear regression to ascertain the interfacial energy of the powder γ.sub.S with the polar component γ.sub.SP and the disperse component γ.sub.SP:

[00002]$\begin{array}{cc}\frac{{\gamma }_L\left(1+\cos \theta \right)}{2{\left({\gamma }_L^D\right)}^{1/2}}={\left({\gamma }_S^P\right)}^{1/2}\frac{{\left({\gamma }_L^P\right)}^{1/2}}{{\left({\gamma }_L^D\right)}^{1/2}}+{\left({\gamma }_S^D\right)}^{1/2}& \left(\mathrm{IX}\right)\end{array}$

[0323] The following relationships should be noted here (formula X and formula XI):

γ.sub.L=γ.sub.L.sup.D+γ.sub.L.sup.P  (X)

γ.sub.S=γ.sub.S.sup.D+γ.sub.S.sup.P

[0324] Meaning of the Variables: [0325] θ contact angle [0326] γ.sub.L interfacial energy of the test liquid [0327] γ.sub.L.sup.D disperse component of the interfacial energy of the test liquid [0328] γ.sub.L.sup.P polar component of the interfacial energy of the test liquid [0329] γ.sub.S interfacial energy of the sinter powder (SP) [0330] γ.sub.S.sup.D disperse component of the interfacial energy of the sinter powder (SP) [0331] γ.sub.S.sup.P polar component of the interfacial energy of the sinter powder (SP)

[0332] Determination of the D50 of the Sinter Powder (SP) and the D90 of the at Least One Flow Agent (Component (B))

[0333] The particle sizes were determined by means of laser diffraction to ISO 13320 (Horiba LA-960, Retsch Technology, Germany), preceded by dry dispersion of the sinter powder (SP) or the at least one flow agent (B) at 1 bar. The evaluation was effected with the aid of the Fraunhofer method.

[0334] Determination of the Dropping Point (Dc) of the at Least One Organic Additive (Component (C))

[0335] The dropping point (Dr) of the organic additives was measured to ISO 2176 with a dropping point measuring instrument (AD0566-600, Scavini, Italy).

[0336] Determination of the Melting Temperature (T.sub.M(SP)) of the Sinter Powder (SP)

[0337] The melting temperature was determined by means of DSC (Differential Scanning calorimetry, Discovery series DSC, TA Instruments) to DIN EN ISO 11357.

[0338] In the DSC measurements, the sample was subjected under a nitrogen atmosphere to the following temperature cycle: 5 minutes at minus 80° C., then heating to at least 200° C. at 20° C./minute (1st heating run (H1)), then 5 minutes at at least 200° C., then cooling to minus 80° C. at 20° C./minute, then 5 minutes at minus 80° C., then heating to at least 200° C. at 20° C./minute (2nd heating run (H2)). The melting temperature (T.sub.M(SP)) then corresponded to the temperature at the maximum of the melting peak of the heating run (H1). If multiple local maxima occur in the range between T.sub.M.sup.onset and T.sub.M.sup.endset, the melting temperature T.sub.M is understood to mean the numerical average of the respective local maxima.

[0339] Determination of the Bulk Density

[0340] The bulk density was determined to DIN EN ISO 60.

[0341] Determination of the Tensile Strength and Elongation at Break

[0342] The determination of the tensile strength and the elongation at break was ascertained with the aid of what is called the tensile test to DIN 53504. The test geometry used was the S2 dumbbell specimen, and the samples were pulled at 200 mm/min (Z010, Zwick/Roell, Germany). For the measurements, specimens were always taken that were printed in X direction, horizontally in the build space layout.

[0343] Determination of the Melt Volume Flow Rate of the Sinter Powder (SP) (MVR)

[0344] The melt volume flow rate was ascertained to DIN EN ISO 1133 (mi2.1, Gottfert, Germany). For this purpose, the sinter powder (SP) was predried under nitrogen at 110° C. for 2 hours and then analyzed with a load of 2.16 kg and at a temperature=(T.sub.M(SP)+40° C.).

Production of the Sinter Powder (SP)

Inventive Example 1 (I1)

[0345] Component (A) was subjected to heat treatment at 100° C. in a dry nitrogen atmosphere for 48 hours. Subsequently, 0.05% by weight of component (B1) and 1% by weight of component (C) were added, and the mixture was processed mechanically to powder under cryogenic conditions (cryogenic comminution) in a pin mill (GSM 250, Gotic, Germany), and then classified by means of a sieving machine (agitated sieve; 0.1×0.3 mm long meshes). After the grinding, another 0.15% by weight of component (B1) was mixed in (Thermomix TMS, Vorwerk; 5 minutes at 2000 revolutions/minute).

Inventive Example 2 (I2)

[0346] For this example, a composition was produced analogously to example 1. After the grinding, 1% by weight of component (C) was additionally mixed in (N,N′-ethylenedi(stearamide), dropping point 142° C.).

Comparative Example 3 (CE3)

[0347] Example 2 from DE 10 2017 124 047 A1 was reworked.

Comparative Example 4 (CE4)

[0348] For this comparative example, a composition was produced analogously to example 1, except that component (C) was not used. This was done by mixing in 0.55% by weight rather than 0.15% by weight of component (B1) after the grinding.

Comparative Example 5 (CE5)

[0349] For this comparative example, a composition was produced analogously to example 1. This was done by additionally adding 5% by weight of component (C) after the grinding.

Comparative Example 6 (CE6)

[0350] Example 1 from EP 3 157 737 B1 was reworked.

[0351] The aforementioned amounts of the components and the properties of the sinter powders (SP) produced are reported in table 2.

TABLE-US-00002 TABLE 2 Example/comparative example I1 I2 CE3 CE4 CE5 CE6 Component (A) (% by wt.) 98.8 97.8 99.8 99.4 93.8 — TPU, synthesized to — — — — — 99.8 EP 3 157 737 B1 (% by wt.) Component (B) 0.2 0.2 0.2 0.6 0.2 0.2 (=B1 + B2 + B3) (% by wt.) Component (C) 1.0 2.0 — — 6.0 — (% by wt.) Bulk density (g/L) 524 526 500 536 529 490 Contact angle 134.2 135.3 126.9 121.4 137.7 125.3 Water (°) Contact angle 124.6 127.1 100.6 95.9 134.3 99.5 Ethylene glycol (°) Contact angle 125.9 127.3 92.8 84.2 131.2 94.5 Formamide (°) Interfacial energy disperse 2.6 2.5 27.7 33.6 1.0 28.6 (mN/m) Interfacial energy polar 0.2 0.2 2.1 2.0 0.4 2.0 (mN/m) Interfacial energy total 2.8 2.5 29.8 35.6 1.4 31.1 (mN/m) Particle size D50 (μm) 79 77 72 71 74 75 Melting point T.sub.M(SP) (° C.) 140 140 140 140 140 130 Melt volume flow rate MVR 49 53 46 47 54 28 (cm.sup.3/10 min) Throughput in production 125 125 30 30 125 20 (grinding + sieving) (kg/h)

[0352] Production of the Shaped Bodies

[0353] The same build space layout was used in each of the manufacturing examples 1 to 6. The build space layout used is shown in FIG. 3. The following parts were accommodated in the build space layout: 37 tensile bars (I) (X and Z orientation), 9 curl crosses (II) and 41 further technical test pieces such as hollow spheres (III), tubes (IV), sheets (V) and other free-form bodies. The free-form bodies served particularly for verification of component quality. In total, the build space layout has 87 test pieces, dimensions of 180×180×226 mm, and a packing density of 7.7%.

[0354] The same build space layout was likewise used in each of the manufacturing examples 10 to 12. This was an adjusted build space layout. This is shown in FIG. 4. The following parts were accommodated in the build space layout: 74 tensile bars (I) (X and Z orientation), 18 curl crosses (II), 120 further technical test pieces such as hollow spheres (III), tubes (IV), sheets (V), grid structures (VI), footwear soles (VII) and other free-form bodies. The free-form bodies served particularly for verification of component quality. In total, the build space layout has 87 test pieces, dimensions of 380×284×371 mm, and a packing density of 7.3%.

Manufacturing Example 1 (M1I1)

[0355] The sinter powder (SP) from inventive example 1 (I1) was processed to shaped bodies by means of a commercial laser sintering machine (Farsoon, HT25IP, China). The processing parameters in the laser sintering operation are given in table 3.

Manufacturing Example 2 (M1I2)

[0356] The sinter powder (SP) from inventive example 2 (I2) was processed to shaped bodies by means of a commercial laser sintering machine (Farsoon, HT251P, China). The processing parameters in the laser sintering operation are given in table 3.

Manufacturing Example 3 (M1CE3)

[0357] The sinter powder (SP) from comparative example 3 (CE3) was processed to shaped bodies by means of a commercial laser sintering machine (Farsoon, HT251P, China). The processing parameters in the laser sintering operation are given in table 3.

Manufacturing Example 4 (M1CE4)

[0358] The sinter powder (SP) from comparative example 4 (CE4) was processed to shaped bodies by means of a commercial laser sintering machine (Farsoon, HT251P, China). The processing parameters in the laser sintering operation are given in table 3.

Manufacturing Example 5 (M1CE5)

[0359] The sinter powder (SP) from comparative example 5 (CE5) was processed to shaped bodies by means of a commercial laser sintering machine (Farsoon, HT251P, China). The processing parameters in the laser sintering operation are given in table 3.

Manufacturing Example 6 (M1CE6)

[0360] The sinter powder (SP) from comparative example 6 (CE6) was processed to shaped bodies by means of a commercial laser sintering machine (Farsoon, HT251P, China). The processing parameters in the laser sintering operation are given in table 3.

TABLE-US-00003 TABLE 3 Manufacturing examples 1 Manufacturing to 6 (except 6) example 6 Laser energy (W) 50 40 Build space 108 95 temperature (° C.) Laser line spacing (mm) 0.10 0.2 Laser speed (m/s) 15 4 Powder layer 0.1 0.15 thickness (mm)

Manufacturing example 10 (M2I1)

[0361] The sinter powder (SP) from inventive example 1 (I1) was processed to specimens by means of a multi-jet fusion machine (HP, HP Jet Fusion 5210 3D Printer, USA). The parameter settings used were ‘Ultrasint TPU01—Balanced’.

Manufacturing Example 11 (M2CE3)

[0362] The sinter powder (SP) from comparative example 3 (CE3) was processed to specimens by means of a multi-jet fusion machine (HP, HP Jet Fusion 5210 3D Printer, USA). The parameter settings used were ‘Ultrasint TPU01—Balanced’.

Manufacturing Example 12 (M2CE5)

[0363] The sinter powder (SP) from comparative example 5 (CE5) was processed to specimens by means of a multi-jet fusion machine (HP, HP Jet Fusion 5210 3D Printer, USA). The parameter settings used were ‘Ultrasint TPU01—Balanced’.

[0364] Reference 1 (R1)

[0365] The values from example 1 of U.S. Pat. No. 8,114,334 B2 were entered as comparative values in table 4.

[0366] The properties of the resultant shaped bodies are compiled in tables 4 and 5.

TABLE-US-00004 TABLE 4 M1 M1 M1 M1 M1 M1 I1 I2 CE3 CE4 CE5 CE6 R1 Sinter powder I1 I2 CE 3 CE4 CE5 CE6 — Tensile strength (MPa) 9.1 8.5 8.1 7.2 6.8 16 2.7 Elongation (%) 360 320 270 220 170 370 170 Processibility* 9.7 9.3 6.3 3.3 3.8 1.2 — Component quality* 9.8 9.2 6.8 4.5 4.9 0.7 — Build stops** 0 0 1 2 1 7 —

TABLE-US-00005 TABLE 5 M2I1 M2CE3 M2CE5 Sinter powder I1 CE3 CE5 Tensile strength (MPa) 9.0 8.3 6.3 Elongation (%) 310 280 180 Processibility* 10 5.7 4.7 Component quality* 9.9 6.4 6.1 Build stops** 0 2 2 *Processibility was monitored by at least three different machine operators during the 10 complete print operations. A complete print operation is understood to mean that the build space layout could be produced in full. Furthermore, the component quality of the shaped bodies that were produced during the aforementioned print operations was examined by the machine operators. Subsequently, processibility and component quality were rated by the machine operators, in each case on a scale from 0 to 10 (10 = best; 1 = worst). The values in tables 5 and 6 correspond to the numerical average of at least three independent assessments. The score of 0 is the lowest assessment. If so many defects were observed during the build that the score would drop below 0, the print operation is stopped (see build stop**). A print attempt is repeated until the build space layout has been produced in full.

[0367] The following defects lead to a reduction in the assessment of processibility: [0368] Flowability problems in the dosage/supply of the pulverulent formulation: −2 points [0369] Problems (inhomogeneities) in the application of the powder layers, for example: [0370] Powder agglomerate formation in/on the powder bed: −1 point [0371] Streaks in the powder bed: −0.5 point (1-3 streaks), −1 point (4-6 streaks), −2 points (>6 streaks); streaks are understood to mean slight, not very deep grooves. [0372] Significant holes or grooves in the powder bed: −1 point (per hole or groove) [0373] Canting/wedging of the application tool (e.g. squeegee, roller): −2 points [0374] ‘Short feeds’ (in the case of a short feed, too little powder is applied as powder layer): −2 points

[0375] The following defects lead to a reduction in the assessment of component quality: [0376] Overmelting of parts owing to significant local buildup of heat in the parts: −1 point [0377] Warpage in manufactured components: −3 points [0378] Surface defects: −1 point (per 3 defects) [0379] Excessively rough surface on the parts: −1 point

[0380] ** In the case of a build stop, the further print operation is prevented because, for example, the powder application system (blade, roll) becomes blocked, parts have risen up (owing to warpage), parts get stuck on the powder application system and/or the powder dosage is/becomes blocked.

[0381] The result of a build stop is that the partly produced moldings have to be discarded and reprinted. This leads to an increase in material loss and an extension of the total build time, which results in an enormous deterioration in economic viability. Therefore, the number of build stops that occurred in the performance of 10 complete build operations (without stoppage) is cited separately. Thus, the number of build stops is not included in the assessment of processibility since a build stop constitutes a manifestly failed process.