Patent ID: 8865304

Claim:
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 μm, (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 −1 .