PRODUCING SEMI-CRYSTALLINE PULVERULENT POLYCARBONATE AND USE THEREOF IN ADDITIVE MANUFACTURING
Ways of preparing a partially crystalline polycarbonate powder are provided that include dissolving an amorphous polycarbonate in a polar aprotic solvent to form a first solution of solubilized polycarbonate at a first temperature. The first solution is then cooled to a second temperature, the second temperature being lower than the first temperature, where a portion of the solubilized polycarbonate precipitates from the first solution to form a second solution including the partially crystalline polycarbonate powder. Certain partially crystalline polycarbonate powders resulting from such methods are particularly useful in additive manufacturing processes, including powder bed fusion processes.
1 . A method of preparing a partially crystalline polycarbonate powder, the method comprising:
dissolving an amorphous polycarbonate in a polar aprotic solvent to form a first solution of solubilized polycarbonate at a first temperature; and
cooling the first solution to a second temperature, the second temperature being lower than the first temperature, wherein a portion of the solubilized polycarbonate precipitates from the first solution to form a slurry comprised of the partially crystalline polycarbonate powder and a less-than-saturated or saturated solution of the polycarbonate, wherein the second temperature is room temperature.
2 . The method of claim 1 , further comprising separating the partially crystalline polycarbonate powder from the slurry.
3 . The method of claim 2 , wherein, prior to or during the separating, a low molecular weight miscible solvent that does not dissolve the polycarbonate is added to the slurry.
4 . The method of claim 3 , wherein the low molecular weight miscible solvent is a C 1 to C 4 alcohol and the separation is performed using filtration.
5 . The method of claim 1 , further comprising repeating the dissolving step using the remainder of the second solution as the polar aprotic solvent and repeating the cooling step to form the second solution including another partially crystalline polycarbonate powder, wherein at least a portion of the polycarbonate dissolved is leftover from the prior dissolving and precipitating.
6 . The method of claim 1 , wherein the polar aprotic solvent is comprised of one or more of the following: dimethyl sulfoxide; diphenyl ether; or anisole.
7 . The method of claim 1 , wherein the polar aprotic solvent consists essentially of one of the following: dimethyl sulfoxide; diphenyl ether; or anisole.
8 . The method of claim 1 , wherein the dissolving step includes heating the amorphous polycarbonate in the polar aprotic solvent to form the first solution of solubilized polycarbonate at the first temperature, the first temperature being greater than room temperature.
9 . The method of claim 8 , wherein the cooling step includes cooling the first solution to the second temperature at a cooling rate, the second temperature being room temperature and the cooling rate being at most about 5° C./min.
10 . The method of claim 1 , wherein the first solution is saturated with amorphous polycarbonate at the first temperature.
11 . The method of claim 1 , wherein the partially crystalline polycarbonate powder has a D 90 particle size of less than about 150 μm and a D 10 of at least 10 μm.
12 . (canceled)
13 . The method of claim 11 , wherein the partially crystalline polycarbonate powder has an average particle diameter from about 30 μm to about 40 μm.
14 . The method of claim 13 , wherein the partially crystalline polycarbonate powder has at least about 90% of the particles by number having a circularity of 0.65 or greater.
15 . (canceled)
16 . The method of claim 14 , wherein the partially crystalline polycarbonate powder has a crystallinity of about 25% to about 35%.
17 . (canceled)
18 . (canceled)
19 . (canceled)
20 . (canceled)
21 . (canceled)
22 . (canceled)
23 . The method of claim 1 , wherein the concentration of the polycarbonate in the first solution is about 5% to about 30% by weight.
24 . (canceled)
25 . The method of claim 1 , wherein the first temperature is from about 100° C. to 150° C.
26 . The method of claim 25 , wherein the first temperature is at most about 145° C.
27 . The method of claim 1 , wherein the dissolving and cooling are carried out under a pressure within 1% of atmospheric pressure.
28 . The method of claim 27 , wherein the dissolving and cooling are carried out under an inert atmosphere.