Method of preparing polymer particles and polymer particles prepared thereby

1. A method of preparing polymer particles, the method comprising

combining a polyetherimide and a solvent at a first temperature to provide a slurry, wherein the polyetherimide is not soluble in the solvent at the first temperature;

heating the slurry to a second temperature and at a pressure effective to dissolve the polyetherimide in the solvent to provide a homogenous solution;

cooling the homogenous solution to a third temperature to provide a dispersion comprising a plurality of polymer particles; and

isolating the polymer particles from the dispersion;

wherein the polymer particles have a Dv90 particle size of less than or equal to 250 micrometers, and

wherein the polyetherimide comprises repeating units of the formula

wherein

at least 90 mole percent of the R groups are para-phenylene and the remaining R groups are each independently the same or different, and are a substituted or unsubstituted C 6-20 aromatic hydrocarbon group, a substituted or unsubstituted, straight or branched chain C 4-20 alkylene group, a substituted or unsubstituted C 3-8 cycloalkylene group, or a combination comprising at least one of the foregoing; and

each Z is independently an aromatic C 6-24 monocyclic or polycyclic group optionally substituted with 1 to 6 C 1-8 alkyl groups, 1 to 8 halogen atoms, or a combination comprising at least one of the foregoing.

2. The method of claim 1 , wherein the polymer particles are substantially spherical in morphology.

3. The method of claim 1 , wherein the first temperature is less than or equal to 100° C.

4. The method of claim 1 , wherein the second temperature is greater than or equal to 200° C., at a pressure of 0.03 to 0.69 MPa.

5. The method of claim 1 , wherein the third temperature is less than or equal to 100° C., and at a pressure of 0 to 0.69 MPa.

6. The method of claim 1 , wherein at least 90 mole percent of the R groups are para-phenylene and the remaining R groups are meta-phenylene.

7. The method of claim 1 , wherein

R is a divalent group of the formula

wherein

Q 1 is —O—, —S—, —C(O)—, —SO 2 —, —SO—, —P(R a )(═O)— wherein R a is a C 1-8 alkyl or C 6-12 aryl, —C y H 2y — or a halogenated derivative thereof;

y is an integer from 1 to 5, or —(C 6 H 10 ) z —;

z is an integer from 1 to 4; and

Z is a group derived from a dihydroxy compound of the formula

wherein

R a and R b are each independently a halogen atom or a monovalent C 1-6 alkyl group;

p and q are each independently integers of 0 to 4;

c is 0 to 4; and

X a is a single bond, —O—, —S—, —S(O)—, —SO 2 —, —C(O)—, or a C 1-18 organic bridging group.

8. The method of claim 1 , wherein each Z is 4,4′-diphenylene isopropylidene.

9. The method of claim 1 , wherein the solvent is an organic solvent comprising ortho-dichlorobenzene, ortho-cresol, meta-cresol, para-cresol, chlorobenzene, bromobenzene, anisole, veratrole, dichlorotoluene, di chlorobenzene, 1,2,4-trichlorobenzene, xylene, toluene, benzene, ethylbenzene, propylbenzene, mesitylene, N-methylpyrrolidinone, dimethylacetamide, dimethylformamide, diphenyl sulfone, diphenylether, phenetole, dimethyl sulfoxide, sulfolane, dimethyl sulfolane, methylene chloride, ethylene tetrachloride, trichloromethane, acetone, methanol, ethanol, cyclopentanone, tetrahydrofuran, or a combination comprising at least one of the foregoing.

10. The method of claim 1 , wherein cooling the homogenous solution is at a constant cooling rate of greater than or equal to 1° C./second.

11. The method of claim 1 , wherein cooling the homogenous solution is by a stepwise cooling process.

12. The method of claim 1 , wherein the slurry has a solids content of less than 40%.

13. The method of claim 1 , wherein isolating the polymer powder is by filtration.

14. The method of claim 1 , wherein the slurry further comprises a surfactant.

15. The method of claim 14 , wherein the surfactant is present in an amount of 0.1 to 10 weight percent based on the total weight of the slurry.

16. The method of claim 1 , where no anti-solvent is used to precipitate the polymer to provide the polymer particles.

17. The method of claim 1 , further comprising washing the isolated polymer particles with an organic solvent.

18. The method of claim 1 , comprising

combining

a polyetherimide comprising repeating units of the formula

 and

a solvent comprising ortho-dichlorobenzene

at a first temperature of 20 to 50° C. to provide a slurry, wherein the polyetherimide is not soluble in the solvent at the first temperature, and the polyetherimide is present in the slurry at a concentration of 1 to 10 wt %;

heating the slurry to a second temperature of 240 to 260° C. and a pressure of 137 to 689 kPa to provide a homogenous solution comprising dissolved polyetherimide and the solvent;

cooling the homogenous solution at a constant rate of 2 to 2.5° C./second to a third temperature of 40 to 60° C. and a pressure of 0 to 689 kPa to provide a dispersion comprising a plurality of polyetherimide particles; and

isolating the polyetherimide particles by filtration;

wherein the polymer particles have a Dv90 particle size of less than or equal to 75 micrometers.

19. A polymer powder prepared by the method of claim 1 , wherein

the polymer powder comprises a plurality of polymer particles having a Dv90 particle size of less than or equal to 250 micrometers;

the polymer particles are substantially spherical in morphology; and

the polymer particles are semi-crystalline.

20. A polymer powder prepared by the method of claim 1 , wherein

the polymer powder comprises a plurality of polymer particles having a Dv90 particle size of less than or equal to 250 micrometers;

the polymer particles are irregularly shaped in morphology; and

the polymer particles are semi-crystalline.