SINTER POWDER (SP) COMPRISING A FIRST POLYAMIDE COMPONENT (PA1) AND A SECOND POLYAMIDE COMPONENT (PA2), WHERE THE MELTING POINT OF THE SECOND POLYAMIDE COMPONENT (PA2) IS HIGHER THAN THE MELTING POINT OF THE FIRST POLYAMIDE COMPONENT (PA1)

Abstract

The present invention relates to a sinter powder (SP) comprising a first polyamide component (PA1) and a second polyamide component (PA2), where the melting point of the second polyamide component (PA2) is higher than the melting point of the first polyamide component (PA1). The present invention further relates to a method of producing a shaped body by sintering the sinter powder (SP) or by an FFF (fused filament fabrication) method, and to a shaped body obtainable by the methods of the invention. The present invention further relates to a method of producing the sinter powder (SP).

Claims

1. A sinter powder (SP) comprising the following components: (A) at least one first polyamide component (PA1) comprising, based on the total weight of the first polyamide component (PA1), at least 50% by weight of a first aliphatic polyamide (aPA1), where the first polyamide component (PA1) has a first melting point (T.sub.M1) and where the first aliphatic polyamide (aPA1) has been formed from repeat units having a first ratio (V1) per repeat unit of CH.sub.2 groups to NHCO groups in the range from 4 to 6, (B) at least one second polyamide component (PA2) comprising, based on the total weight of the second polyamide component (PA2), at least 50% by weight of a second aliphatic polyamide (aPA2), where the second polyamide component (PA2) has a second melting point (T.sub.M2) and where the second aliphatic polyamide (aPA2) has been formed from repeat units having a second ratio (V2) per repeat unit of CH.sub.2 groups to NHCO groups in the range from 4 to 6, where the second melting point (T.sub.M2) is higher than the first melting point (T.sub.M1) and where the quotient (Q) of the numerical value of the second ratio (V2) divided by the numerical value of the first ratio (V1) is in the range from 0.6 to 1.5.

2. The sinter powder (SP) according to claim 1, wherein the differential between second melting point (T.sub.M2) and first melting point (T.sub.M1) is in the range from 20 to 70 K.

3. The sinter powder (SP) according to claim 1, wherein the second melting point (T.sub.M2) is in the range from 170 to 300° C. and the first melting point (T.sub.M1) is in the range from 150 to 280° C.

4. The sinter powder (SP) according to claim 1, wherein the sinter powder (SP) comprises: 5% to 95% by weight of component (A), 5% to 95% by weight of component (B), 0% to 5% by weight of at least one free flow aid, 0% to 5% by weight of at least one additive and 0% to 40% by weight of at least one reinforcer, based in each case on the total weight of the sinter powder (SP).

5. The sinter powder (SP) according to claim 1, wherein the first ratio (V1) is in the range from 4.5 to 5.5, and the second ratio (V2) is in the range from 4.5 to 5.5, and the quotient (Q) is in the range from 0.8 to 1.2.

6. The sinter powder (SP) according to claim 1, wherein the first aliphatic polyamide (aPA1) is at least one aliphatic polyamide selected from the group consisting of PA6/66, PA6 and PA66/6 and the second aliphatic polyamide (aPA2) is at least one aliphatic polyamide selected from the group consisting of PA6, PA66/6 and PA66.

7. The sinter powder (SP) according to claim 1, wherein the first polyamide component (PA1) comprises 50% to 90% by weight of the first aliphatic polyamide (aPA1) selected from the group consisting of PA6/66, PA6 and PA66/6 and 10% to 50% by weight of a first (semi)aromatic polyamide (arPA1), based on the total weight of the first polyamide component (PA1), and the second polyamide component (PA2) comprises 50% to 90% by weight of the second aliphatic polyamide (aPA2) selected from the group consisting of PA6, PA66/6 and PA66 and 10% to 50% by weight of a second (semi)aromatic polyamide (arPA2), based on the total weight of the second polyamide component (PA2).

8. The sinter powder (SP) according to claim 1, wherein the sinter powder (SP) has a median particle size (D50) in the range from 10 to 250 μm.

9. The sinter powder (SP) 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.

10. The sinter powder (SP) 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.M2.sup.onset) and the onset temperature of crystallization (T.sub.C2.sup.onset) and where the sintering window (W.sub.SP) is in the range from 10 to 40 K.

11. The sinter powder (SP) according to claim 1, wherein the sinter powder (SP) comprises 10% to 90% by weight of component (A), 10% to 90% by weight of component (B), 0.1% to 1% by weight of at least one free flow aid, 0.1% to 2.5% by weight of at least one additive, and 0% to 40% by weight of at least one reinforcer, based in each case on the total weight of the sinter powder (SP).

12. A method of producing a shaped body, comprising the steps of: is) providing a layer of the sinter powder (SP) according to claim 1, iis) exposing the layer of the sinter powder (SP) provided in step is) in order to form the shaped body.

13. A method of producing a shaped body, comprising the steps of: if) melting the sinter powder (SP) according to claim 1, iif) depositing the molten sinter powder (SP) in a construction space in order to form the shaped body.

14. The use of the sinter powder (SP) according to claim 1 in a sintering method or in a fused filament fabrication method.

15. A method of producing the sinter powder (SP) according to claim 1, comprising the steps of a) providing the first polyamide component (PA1) b) providing the second polyamide component (PA2) c) mixing the first polyamide component (PA1) and the second polyamide component (PA2).

16. The sinter powder (SP) according to claim 1, further comprising: (C) at least one free-flow aid, (D) at least one additive, and (E) at least one reinforcer.

17. The sinter powder (SP) according to claim 5, wherein the first ratio (V1) is in the range from 4.8 to 5.2, the second ratio (V2) is in the range from 4.8 to 5.2, and the quotient (Q) is in the range from 0.9 to 1.1.

18. The sinter powder (SP) according to claim 5, wherein the first ratio (V1) is in the range from 4.9 to 5.1, the second ratio (V2) is in the range from 4.9 to 5.1, and the quotient (Q) is in the range from 0.96 to 1.04.

19. The sinter powder (SP) according to claim 5, wherein the first ratio (V1) is in the range from 4.95 to 5.05, the second ratio (V2) is in the range from 4.95 to 5.05, and the quotient (Q) is in the range from 0.98 to 1.02.

Description

EXAMPLES

[0182] The following powders are used:

Powder (P1)

[0183] First polyamide component (PA1) comprising 78.6% by weight of PA6 (nylon-6, Ultramid® B27E, BASF SE), 21% by weight of PA6 I/6T (nylon-6I/6T, Grivory G16, EMS) and 0.4% by weight of Irganox 1098® (component (D), N,N′-hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide)), BASF SE), percentages by weight based in each case on the total weight of component (A)

Powder (P2)

[0184] Second polyamide component (PA2) comprising 78.5 weight of PA66 (nylon-6,6, Ultramid® A27, BASF SE), 21% by weight of PA6 I/6T (nylon-6I/6T, Grivory G16, EMS) and 0.5% by weight of Irganox 1098@ (component (D), N,N′-hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide)), BASF SE), percentages by weight based in each case on the total weight of component (B)

Powder (P3)

[0185] Powder (P3) is a mixture of 75% by weight of powder (P1) with 25% by weight of glass beads (Spheriglass 3000 CPO3, Potters).

[0186] Table 1 reports the particle sizes and also melting points and crystallization temperatures of powders (P1), (P2), (P3) and of a 70:30 mixture and of a 50:50 mixture of (P1) and (P2).

[0187] Powders (P1), (P2), (P3) and mixtures of powders (P1) and (P2) were used to produce shaped bodies (80 mm×10 mm×4 mm sintered specimens) by selective laser sintering. The construction space temperature was 200° C.; the energy input of the laser was 40 mJ/mm.sup.2.

[0188] The measurement results for the sintered specimens are shown in table 2.

[0189] Particle sizes, melting points and crystallization temperatures were determined as described above in the description.

[0190] The softening temperature “Vicat B50” was determined as follows: measurement to ISO 306:2013 at a heating rate of 50 K/h, sample thickness 4 mm and silicone oil as heat transfer medium.

[0191] The heat deflection temperature “HDT” was determined as follows: measurement to ISO 72-2:2013 at a heating rate of 120 K/h, span 64 mm, dried samples (80° C., reduced pressure, 336 hours).

TABLE-US-00002 TABLE 1 D50 D90 T.sub.M1 T.sub.C1 T.sub.M2 T.sub.C2 Example [μm] [μm] [μm] [° C.] [° C.] [° C.] [° C.] P1 47.0 75.0 117.0 218.0 173.0 — — P2 17.9 45.1  84.3 — — 258.0 224.0 P3 n.d. n.d. n.d. 218   175   — — P1/P2 35.1 67.8 116.1 217.9 178.2 257.5 212.0 50/50 P1/P2 n.d. n.d. n.d. 219.4 174.2 256.5 214.5 70/30

TABLE-US-00003 TABLE 2 T.sub.C1 T.sub.C2 Color P1 [% P2 [% P3 [% Vicat HDTA Sintered Sintered [° C.]Sintered [° C.]Sintered Sintered Separation Example by wt.] by wt.] by wt.] B50 [° C.] [° C.] specimen specimen specimen specimen specimen Powder VP1 100.0  — — 193.0  98.0 220.7 n.d. 170.9 n.d. white no EB1 85.0 15.0 — n.d. n.d. n.d. n.d. n.d. n.d. white no EB2 70.0 30.0 — 198.1- n.d. 219.4 258.5 174.2 214.5 white no 199.6 EB3 50.0 50.0 n.d. n.d. n.d. n.d. n.d. n.d. n.d. white no EB4 80.0 20.0 — n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. VP2 — 100.0  — 224.0 n.d. 259.1 n.d. 225.3 n.d. dark no brown — — 100.0 194.0 104.0 219.5 n.d. 172.1 n.d. white- yes greenish

[0192] The DSC measurements on the sintered specimens show that the co-melting has given rise to partly compatible mixtures. This becomes clear from an increase in the first crystallization temperature T.sub.C1 and a lowering of the second crystallization temperature T.sub.C2. The Vicat softening temperature is higher for EB2 than for VP1; it is additionally higher than in the case of VP3. In the case of the sinter powders (SP) of the invention, moreover, no separation of the powders was observed, as is the case for VP3. White sintered specimens are obtainable from the sinter powders (SP) of the invention.

[0193] The prior art (Mechanical properties of PA6/PA12 blend specimens prepared by selective laser sintering, Polymer Testing 31 (2012) 411-416, doi:10.1016) describes the mechanical properties of shaped bodies that have been produced by selective laser sintering from polyamide powders. This document compares the mechanical properties of pure PA6 powder and pure PA12 powder with PA6/PA12 powder mixtures. This document discloses that, in the case of a 50:50 polyamide powder mixture of PA6:PA12, a deterioration in impact resistance of 78% is measured, based on the ultimate strength of a shaped body which is produced from a pure PA12 powder. For a polyamide powder mixture PA6/PA12 of 20:80, a deterioration in ultimate strength of 47% is observed, likewise based on the ultimate strength of a shaped body that has been produced from a pure PA12 powder.

[0194] Table 3 below shows the test results for the ultimate strengths for sintered specimens that have been produced from pure PA6 powder (see comparative example VP1) or from the sinter powders (SP) of the invention. EB1 shows the ultimate strength of a sintered specimen that has been prepared from a P1:P2 powder mixture of 85:15% by weight. Inventive example EB4 shows the ultimate strength of a sintered specimen that has been prepared from a P1:P2 powder mixture of 80:20% by weight. Inventive example EB2 shows the strength of a sintered specimen that has been prepared from a sinter powder (SP) P1:P2 of 70:30% by weight.

[0195] For the inventive examples, ultimate strength was measured in the dry state to ISO 527-2:2012. For sintered specimens that have been produced from pure PA6 powder, a ultimate strength of 57.7 MPa was ascertained. For the sintered specimens that have been produced by laser sintering of the inventive powder mixtures EB1, EB2 and EB4, ultimate strengths of 51.8, 42 and 47.9 MPa respectively were ascertained. Thus, based on sintered specimens that have been produced from pure PA6 powder, the decrease in ultimate strength is only 10.2%, 27.2% and 17.0% respectively, and hence much lower than in the case of sintered specimens that have been produced from powder mixtures according to the prior art. The determination of the ultimate strength of a sintered specimen that has been produced from a pure PA66 powder (see VP2) was not possible in the present case since the sintering of the powder (VP2) gave only very poor, highly discolored and hence untestable sintered specimens.

TABLE-US-00004 TABLE 3 Standard deviation P1 [% P2 [% Ultimate in ultimate Example by wt.] by wt.] strength [MPa] strength [MPa] 100.0 — 57.7 2.0 EB1 85.0 15.0 51.8 1.0 EB2 70.0 30.0 42.0 1.8 EB4 80.0 20.0 47.9 2.0 VP2 — 100.0 n.d. n.d.