Process for the manufacture of flame retardant polycarbonate particles and flame retardant polycarbonate particles prepared thereby

1. A process for the manufacture of polycarbonate particles, the process comprising:

combining a first solution comprising

(i) a polycarbonate and a phosphorus-containing flame retardant, and

(ii) an organic solvent

with a second solution comprising

(i) a surfactant and

(ii) an aqueous solvent substantially immiscible with the organic solvent, under conditions of shear and temperature effective to provide an emulsion; and

removing at least a portion of the organic solvent to provide an aqueous slurry comprising a plurality of particles comprising the polycarbonate and the phosphorus-containing flame retardant.

2. The process of claim 1 , wherein

the polycarbonate is a homopolycarbonate, a copolycarbonate, a polycarbonate copolymer, or a combination comprising at least one of the foregoing.

3. The process of claim 1 , wherein the first solution comprises 10 to 30 weight percent of the polycarbonate, based on the total weight of the polycarbonate and the organic solvent.

4. The process of claim 1 , wherein the phosphorus-containing flame retardant comprises an aromatic group, a phosphorus-nitrogen bond, or a combination comprising at least one of the foregoing.

5. The process of claim 1 , wherein the phosphorus-containing flame retardant is present in the first solution in an amount effective to provide 0.05 to 5 weight percent of phosphorus, based on the combined weight of the polycarbonate and the phosphorus-containing flame retardant.

6. The process of claim 1 , wherein a boiling point of the organic solvent is less than 100° C., and wherein the organic solvent is substantially immiscible with water.

7. The process of claim 1 , wherein the surfactant comprises an anionic surfactant, a biopolymer surfactant, or a combination comprising at least one of the foregoing,

wherein the anionic surfactant is a (C 8-36 alkyl)benzene sulfonate, (C 8-36 alkyl) sulfonate, mono- or di(C 8-36 alkyl) sulfosuccinate, (C 8-36 alkyl ether) sulfate, (C 8-36 )alkyl ether sulfonate, perfluoro(C 2-12 alkyl) sulfate, or perfluoro(C 2-12 carboxylate); and

wherein the biopolymer is gelatin.

8. The process of claim 1 , wherein

a weight ratio of the polycarbonate to the phosphorus-containing flame retardant is 99:1 to 50:50;

the emulsion comprises water in a water to organic solvent weight ratio of greater than or equal to 0.4:1 to 1.25:1; and

the emulsion comprises the surfactant in a surfactant to polycarbonate weight ratio of 0.008:1 to 0.04:1.

9. The process of claim 1 , wherein removing at least a portion of the organic solvent comprises exposing the emulsion to heat by adding the emulsion into a receiving water, wherein the receiving water is at a temperature of 25 to 90° C.

10. The process of claim 1 , wherein removing at least a portion of the organic solvent comprises exposing the emulsion to heat by heating the emulsion to a temperature of 25 to 90° C. to provide the slurry.

11. The process of claim 10 , wherein the heating is conducted until 70% to 95% of the organic solvent is removed to provide the slurry; and the method further comprises agitating the slurry without heating to remove the remaining organic solvent.

12. The process of claim 1 , wherein removing at least a portion of the organic solvent comprises purging the emulsion with air, nitrogen, argon, or a combination comprising at least one of the foregoing in the absence of heat.

13. The process of claim 1 , further comprising passing the aqueous slurry comprising the plurality of particles through a filter, to provide micronized particles having at least one of:

a Dv90 of 5 to 140 micrometers;

a Dv50 of 3 to 60 micrometers;

a Dv10 of 0.1 to 20 micrometers; or

a particle size distribution span of 1.05 to 3.5;

wherein Dv90, Dv50, Dv10 and particle size distribution span are determined by laser diffraction.

14. The process of claim 1 , wherein the polycarbonate particles are recovered in a yield greater than 25%.

15. The process of claim 1 , wherein the polycarbonate particles have a glass transition temperature of less than or equal to 140° C., determined using differential scanning calorimetry.

16. The process of claim 7 , wherein the polycarbonate particles have a residual gelatin content of less than 1000 parts per million.

17. The process of claim 1 , wherein the polycarbonate particles retain greater than 90% of the phosphorus-containing flame retardant present in the first solution.

18. Polycarbonate particles comprising a phosphorus-containing flame retardant, produced by the process of claim 1 ;

wherein the polycarbonate particles have at least one of:

a Dv90 of 5 to 140 micrometers;

a Dv50 of 3 to 60 micrometers;

a Dv10 of 0.1 to 20 micrometers; or

a particle size distribution span of 1.05 to 3.5; and

wherein Dv90, Dv50, Dv10 and particle size distribution span are determined by laser diffraction.

19. Polycarbonate particles comprising:

a polycarbonate and resorcinol bis (diphenyl phosphate);

wherein the polycarbonate particles have at least one of:

a Dv90 of 5 to 140 micrometers;

a Dv50 of 3 to 60 micrometers;

a Dv10 of 0.1 to 20 micrometers; or

a particle size distribution span of 1.05 to 3.5;

wherein Dv90, Dv50, Dv10 and particle size distribution span are determined by laser diffraction;

wherein the polycarbonate particles have a glass transition temperature of less than or equal to 140° C., determined using differential scanning calorimetry; and

wherein the polycarbonate particles have a residual gelatin content of less than 1000 parts per million.

20. An article comprising the polycarbonate particles of claim 18 .