Polyamide composition containing a polyamide and an additive

Abstract

The present invention relates to a polyamide composition (PC) which comprises at least one polyamide (P) and at least one additive (A). The present invention further relates to the use of the polyamide composition (PC) in a selective laser sintering process, in an injection molding process, for producing molded articles and in an extrusion process.

Claims

1. A polyamide composition (PC) which comprises at least one polyamide (P) and at least one additive (A), wherein the at least one additive (A) is selected from compounds of general formula (I) ##STR00003## in which R.sup.1 and R.sup.3 are independently of one another selected from the group consisting of H, C.sub.1- to C.sub.10-alkyl and NR.sup.5R.sup.6, wherein R.sup.5 and R.sup.6 are independently of one another selected from the group consisting of H and C.sub.1- to C.sub.10-alkyl; R.sup.2 and R.sup.4 are independently of one another selected from the group consisting of H, C.sub.1- to C.sub.10-alkyl and NR.sup.7R.sup.8, wherein R.sup.7 and R.sup.8 are independently of one another selected from the group consisting of H and C.sub.1- to C.sub.10-alkyl; X represents N, O.sup.+ or S.sup.+; wherein the compounds of general formula (I) have a positive charge when X represents O.sup.+ or S.sup.+ and the compounds of general formula (I) then comprise an anion Y.sup.−, wherein Y.sup.− is selected from the group consisting of hydroxide, chloride, bromide, iodide, sulfate, sulfite, phosphate and phosphite, wherein the polyamide composition (PC) is present in the form of a powder having a particle size in the range from 1 to 200 μm, wherein the composition is a sintering powder; and wherein the polyamide composition (PC) comprises in the range from 95 to 99.9 wt % of the at least one polyamide (P) and in the range from 0.1 to 5 wt % of the at least one additive (A) in each case based on the sum of the weight percentages of the at least one polyamide (P) and of the at least one additive (A); wherein the polyamide composition has a D10 value in the range of from 10 to 30 μm.

2. The composition according to claim 1, wherein the at least one polyamide (P) present in the polyamide composition (PC) 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 510, PA 610, PA 612, PA 613, PA 1212, PA 1313, PA 6T, PA MXD6, PA 61, PA 6-3-T, PA 6/6T, PA 6/66, PA 66/6, PA 6/12, PA 66/6/610, PA 61/6T, PA PACM 12, PA 61/6T/PACM, PA 12/MACMI, PA 12/MACMT, PA PDA-T and copolyamides composed of two or more of the abovementioned polyamides.

3. The composition according to claim 1, wherein the at least one polyamide (P) present in the polyamide composition (PC) is selected from the group consisting of polyamide 6 (PA 6), polyamide 66 (PA 66), polyamide 6/66 (PA 6/66), polyamide 66/6 (PA 66/6), polyamide 610 (PA 610), polyamide 6/6T (PA 6/6T), polyamide 12 (PA12) and polyamide 1212 (PA1212).

4. The composition according to claim 1, wherein the substituents of the compounds of general formula (I) are defined as follows: R.sup.1 and R.sup.3 are independently of one another selected from the group consisting of H and C.sub.1- to C.sub.5-alkyl; R.sup.2 and R.sup.4 are independently of one another selected from the group consisting of C.sub.1- to C.sub.5-alkyl and NR.sup.7R.sup.8, wherein R.sup.7 and R.sup.8 are independently of one another selected from the group consisting of H and C.sub.1- to C.sub.5-alkyl; X is N or S.sup.+, wherein the compounds of general formula (I) have a positive charge when X represents S.sup.+ and the compounds of general formula (I) then comprise an anion Y.sup.−, wherein Y.sup.− is selected from the group consisting of hydroxide, chloride, bromide and iodide.

5. The composition according to claim 1, wherein the at least one additive (A) present in the polyamide composition (PC) is selected from the group consisting of neutral red and methylene blue.

6. The composition according to claim 1, wherein the polyamide composition (PC) comprises further additives (fA), wherein the further additives (fA) are selected from the group consisting of stabilizers, dyes, pigments, fillers, reinforcers, impact modifiers and plasticizers.

7. The composition according to claim 1, wherein the polyamide composition (PC) comprises in the range from 0.1 to 60 wt % of further additives (fA) based on the total weight of the polyamide composition (PC).

8. A method comprising selective laser sintering the polyamide composition (PC) according to claim 1.

9. A method comprising producing a molded article from the polyamide composition (PC) according to claim 1.

Description

EXAMPLES

(1) The following components were employed:

(2) Polyamide (P):

(3) (P1) Polyamide 12 (PA 2200, EOS) (P2) Polyamide 6 (Ultramid® B27; BASF SE)
Additive (A) (A1) Neutral red (3-amino-7-dimethylamino-2-methylphenazine hydrochloride; Carl Roth, Fluka, Alfa Aesar)
Production of the Sintering Powder

(4) Table 1 indicates whether the sintering powder was produced by precipitation or by grinding.

(5) For the sintering powders produced by grinding the components reported in table 1 were compounded in the ratio reported in table 1 in a twin-screw extruder (ZSK 40) at 200 rpm, a barrel temperature of 240° C. and a throughput of 50 kg/h with subsequent extrudate pelletization. The thus obtained pelletized material was subjected to cryogenic grinding to obtain the sintering powder (SP).

(6) To produce the sintering powder by precipitation the polyamide (P) was dissolved in the amounts reported in table 1 in a solvent consisting of 40 wt % of caprolactam and 60 wt % of water in each case based on the total weight of the solvent using a temperature ramp of 2 hours at 120° C., 2 hours at 160° C. and 0.5 hour at 175° C. and subsequently precipitated by cooling. After washing with water and drying, the polyamide (P) was obtained as a powder. The thus obtained powder of the polyamide (P) was subsequently contacted with a solution of the additive (A), the polyamide (P) and the additive (A) being employed in the ratio reported in table 1. The solvent employed in the solution of the additive (A) was water. After drying the sintering powder (SP) was obtained.

(7) TABLE-US-00001 TABLE 1 (P1) (P2) (A1) Example [wt %] [wt %] [wt %] Production C1 100 — — — C2 — 100 — grinding C3 100 precipitation E4 — 99.875 0.125 precipitation E5 99.5 0.5 precipitation

(8) The onset temperature of melting (T.sub.M.sup.onset) and the onset temperature of crystallization (T.sub.C.sup.onset) of the sintering powder were determined as described for FIG. 1. The sintering window (W) was determined therefrom.

(9) Tensile bars were also produced to determine warpage.

(10) Production of Tensile Bars

(11) The sintering powders were introduced with a layer thickness of 0.1 mm into the construction space at the temperature reported in table 2. The sintering powder was subsequently irradiated with a laser with the laser power output reported in table 2 and the reported point spacing, wherein the speed of the laser over the sample during irradiation was as reported in table 2. The point spacing is also known as laser track spacing or lane spacing. In selective laser sintering scanning is typically effected in stripes. The point spacing denotes the distance between the centers of the stripes, i.e. between the two centers of the laser beam of two stripes.

(12) TABLE-US-00002 TABLE 2 Laser power Temperature output Laser speed Point spacing Example [° C.] [W] [m/s] [mm] C1 171 11 5 0.15 C2 209 18 5 0.2 C3 201 23 5 0.2 E4 201 18 5 0.15 E5 208 15 5 0.15
Determination of Warpage

(13) To determine the warpage of the obtained sintered bars the sintered bar was placed concave side down on a planar surface. The distance (a.sub.m) between the planar surface and the upper edge of the middle of the sintered bar was then determined. The thickness (d.sub.m) in the middle of the sintered bar was also determined. Warpage in % is then given by the following formula:
V=100.Math.(a.sub.m−d.sub.m)/d.sub.m

(14) The dimensions of the sintered bars were typically 80 mm in length, 10 mm in width and 4 mm in thickness.

(15) The results for the measurement of the sintering window (W) and of warpage are reported in table 3.

(16) TABLE-US-00003 TABLE 3 Sintering T.sub.m.sup.onset T.sub.c.sup.onset window W Warpage Example [° C.] [° C.] [K] [%] C1 178.7 152.5 26.2 — C2 207.4 190.7 10.7 50 C3 214.1 188.8 25.3 20 E4 213.2 181.3 31.9 — E5 211.5 175.6 35.9  5

(17) It is clearly apparent from table 3 that the use of at least one additive (A) in the sintering powder (SP) results in a markedly widened sintering window. In addition, warpage is markedly reduced.