Biodegradable aliphatic polyester particles and production process thereof

• US 8,865,304 B2
• Filed: 04/20/2012
• Issued: 10/21/2014
• Est. Priority Date: 04/22/2011
• Status: Expired due to Fees

• Current Assignee: Kureha Corporation
• Original Assignee: Kureha Corporation
• Inventors: Yamazaki, Masahiro, Abe, Shunsuke, Kuruhara, Nanako, Saigusa, Kotaku, Sato, Hiroyuki
• Primary Examiner(s): PATEL, RONAK C
• Application Number:
  US13/452,119
• Publication Number:
  US 20120270048A1
• Time in Patent Office: 914 Days
• Field of Search: None
• US Class Current: 428/402
• CPC Class Codes: C08G 63/08 Lactones or lactides
• CPC Class Codes: C08G 63/88 Post-polymerisation treatment
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

Biodegradable aliphatic polyester particles have: (A) an average particle diameter of 10 to 500 μm, and (B) a quantity of heat of low-temperature crystallization calculated as an exotherm attending on crystallization, detected in the course of heating by DSC, of at least 1 J/g, and preferably: (C) a quantity of heat of crystal melting calculated as an endotherm attending on melting of a crystal, detected in the course of the heating, of less than 100 J/g, and (D) a difference between the quantity of heat of crystal melting and the quantity of heat of low-temperature crystallization of less than 90 J/g. A process for producing the particles comprises grinding a particular biodegradable aliphatic polyester having a weight average molecular weight of at least 50,000 at not lower than 0° C. and lower than the glass transition temperature of the polyester while applying high shearing force.

Claims

1. Biodegradable aliphatic polyester particles, wherein the particles are soluble in an organic solvent at a temperature of 40°

C. or lower and wherein;

(A) a biodegradable aliphatic polyester contained in the biodegradable aliphatic polyester particles is a polyglycolic acid having a weight average molecular weight of from 150,000 to 1,000,000,

(B) the average particle diameter (50% D) of the particles is 10 to 500 μ

m,

(C) the quantity of heat of low-temperature crystallization thereof as calculated out as an exotherm attending on crystallization, which is detected in the course of heating by a differential scanning calorimeter, is at least 1 J/g,

(D) the quantity of heat of crystal melting thereof as calculated out as an endotherm attending on melting of a crystal, which is detected in the course of heating by the differential scanning calorimeter, is less than 100 J/g,

(E) the biodegradable aliphatic polyester particles can be dissolved at a concentration of at least 2% by mass in an organic solvent at a temperature not higher than the glass transition temperature (Tg) of the biodegradable aliphatic polyester contained in the biodegradable aliphatic polyester particles−

5°

C., to prepare a solution, and

(F) solution viscosity is within a range of from 10 to 1,000 mPa·

s, wherein the solution viscosity is determined by pouring 2 g of the biodegradable aliphatic polyester particles into 20 ml of hexafluoroisopropanol, stirring the resultant mixture for 2 hours while keeping the temperature of the system at 25°

C., thereby preparing a solution, and conducting measurement on the solution at a temperature of 25°

C. and a shear rate of 20 sec<sup>−

1</sup>.

2. The biodegradable aliphatic polyester particles according to claim 1, wherein the organic solvent is at least one solvent selected from the group consisting of ester solvent, dibasic acid ester solvent, ketone solvent, hydrocarbon solvent, halogen-containing solvent, alcohol solvent, ether solvent, amide solvent, and pyrrolidone solvent.

3. The biodegradable aliphatic polyester particles according to claim 1, wherein the average particle diameter thereof is 12 to 450 μ

m.

4. The biodegradable aliphatic polyester particles according to claim 1, wherein the average particle diameter thereof is 20 to 300 μ

m.

5. The biodegradable aliphatic polyester particles according to claim 1, wherein the average particle diameter thereof is 30 to 200 μ

m.

6. The biodegradable aliphatic polyester particles according to claim 1, wherein the particles are soluble in an organic solvent at a temperature of 35°

C. or lower.

7. The biodegradable aliphatic polyester particles according to claim 1, wherein the particles are soluble in an organic solvent at a temperature of 30°

C. or lower.

8. The biodegradable aliphatic polyester particles according to claim 1, wherein the particles are soluble in an organic solvent at a temperature of 20 to 25°

C.

9. The biodegradable aliphatic polyester particles according to claim 1, wherein the particles can be dissolved at a concentration of at least 3% by mass in an organic solvent at a temperature not higher than the glass transition temperature (Tg) of the biodegradable aliphatic polyester contained in the biodegradable aliphatic polyester particles−

5°

C., to prepare a solution.

10. The biodegradable aliphatic polyester particles according to claim 1, wherein the particles can be dissolved at a concentration of at least 4% by mass in an organic solvent at a temperature not higher than the glass transition temperature (Tg) of the biodegradable aliphatic polyester contained in the biodegradable aliphatic polyester particles−

5°

C., to prepare a solution.

11. The biodegradable aliphatic polyester particles according to claim 1, wherein the particles can be dissolved at a concentration of at least 5% by mass in an organic solvent at a temperature not higher than the glass transition temperature (Tg) of the biodegradable aliphatic polyester contained in the biodegradable aliphatic polyester particles−

5°

C., to prepare a solution.

12. The biodegradable aliphatic polyester particles according to claim 1, wherein the solution viscosity is within a range of from 50 to 800 mPa·

s.

13. The biodegradable aliphatic polyester particles according to claim 1, wherein the solution viscosity is within a range of from 100 to 600 mPa·

s.

14. The biodegradable aliphatic polyester particles according to claim 1, wherein the solution viscosity is within a range of from 150 to 500 mPa·

s.

15. The biodegradable aliphatic polyester particles according to claim 1, wherein (G) a difference between the quantity of heat of crystal melting and the quantity of heat of low-temperature crystallization is less than 90 J/g.

16. A process for producing the biodegradable aliphatic polyester particles according to claim 1, which comprises grinding a particular biodegradable aliphatic polyester containing a polyglycolic acid at a temperature not lower than 0°

C. and lower than the glass transition temperature of the biodegradable aliphatic polyester while applying high shearing force.