Process for preparing a bio-resorbable polyester in the form of a powder

1. A process for preparing a bio-resorbable polyester in the form of a powder, wherein the bio-resorable polyester has

a bulk density of 0.3 g/ml or more,

a tapped density of 0.4 g/ml or more and

a specific surface area of 2.0 m 2 /g or less

the process comprising:

(a) dissolving a bio-resorbable polyester in a first solvent to form a polymer solution,

(b) contacting the polymer solution with a second solvent to result the precipitation of the bio-resorbable polyester in the form of a wet polymer mass, wherein said second solvent comprises water or is a mixture of more than 50% water and the balance of a water soluble solvent,

(c) pre-drying the wet polymer mass at a temperature below the T gO of the bio-resorbable polyester,

(d) comminuting the pre-dried polymer mass to polymer particles with a size below 10 mm,

(e) drying the comminuted polymer particles at a temperature below the T gO of the bio-resorbable polyester to a residual water content of 1% or less by weight/weight,

(f) performing post-treatment of the polymer particles from the drying (e) at a temperature in the range from the T gO to the T gE of the bio-resorbable polyester, and

(g) comminuting the polymer particles from the post-treatment (f) to a powder with a particle size of d 50 of 1-300 μm and d 90 of more than 30 and up to 3000 μm.

2. The process according to claim 1 , wherein the bio-resorbable polyester is a polylactic acid, a polyglycolic acid, a poly-caprolactone, a lactic acid-glycolic acid copolymer, a lactic acid-glycolic acid-polyethylene blockcopolymer, a lactic acid-glycolic acid-caprolactone terpolymer, a lactic acid-caprolactone copolymer, a poly dioxanone or a lactic acid-trimethylene carbonate copolymer or any blend of the polymers.

3. The process according to claim 1 , wherein the bio-resorbable polyester is a poly(D,L-lactide-co-glycolide) copolymer with an inherent viscosity from 0.1-2.0.

4. The process according to claim 3 , wherein the proportion of D,L-lactide to glycolide in the poly(D,L-lactide-co-glycolide) copolymer is from 70:30 to 30:70 parts by weight.

5. The process according to claim 1 , wherein the second solvent is a mixture of more than 60% water and the balance of a water soluble solvent.

6. The process according to claim 1 , wherein the second solvent is a mixture of more than 70% water and the balance of a water soluble solvent.

7. The process according to claim 1 , wherein the second solvent is a mixture of more than 80% water and the balance of a water soluble solvent.

8. The process according to claim 1 , wherein the second solvent is a mixture of more than 90% water and the balance of a water soluble solvent.

9. The process according to claim 1 , wherein the polymer mass in the pre-drying (c) is dried to a residual water content measured as loss on drying from 30 to 70% by weight/weight.

10. The process according to claim 1 , wherein at least one of the pre-drying (c), the drying (e), or the post-treatment (f) are performed in a fluidized bed drying equipment.

11. The process according to claim 1 , wherein the polymer particles in the post-treatment (f) are dried at a temperature in a range from the T gO to the T gE E of the bio-resorbable polyester.

12. The process according to claim 1 , wherein the polymer particles in the post-treatment (f) are dried to a residual water content measured by the Karl Fischer method of 0.5% or less by weight/weight.