Readily absorbable copolymer compositions for high strength sutures having enhanced strength retention post-implantation

A method of making an absorbable copolymer of the structure A-B-A comprising end segments A and middle segment B, wherein end-segments A comprise polymerized glycolide and the middle segment B comprises a polymerized glycolide and lactide, comprising the steps of:

• A) forming a fully amorphous prepolymer reaction product, which will result in a precursor to middle segment B, by polymerizing about 30 mole percent to about 80 mole percent of polymerized lactide and about 20 mole percent to about 70 mole percent of polymerized glycolide at a temperature between about 175° C. to about 195° C., in the presence of diethylene glycol as an initiator having concentration between 500:1 to 1,500:1 (mole of monomer:
• mole of initiator), and in the presence of a catalyst in the total amount of 50,000:1 to 300,000:1 (moles of monomer:moles of catalyst), for total reaction time of the first stage between 120 minutes and 180 minutes;
• B) adding additional glycolide monomer in solid or molten form into the reaction product of the previous step in the reactor vessel with a first agitation speed sufficient to allow complete mixing of the prepolymer and added glycolide monomer within about 30 minutes to 90 minutes;
• C) increasing the reactor batch temperature up to about 205° C. to 210° C., and,
• D) lowering the agitation to a second agitation speed, which is about 40 percent to about 70 percent lower than the first agitation speed until sufficient conversion is achieved as measured by real-time FT-NIR remote spectroscopy, with total time of about 150 minutes to 240 minutes after the glycolide addition of step B above,
• wherein the total amount of polymerized glycolide is about 88 mole percent to about 92 mole percent of said absorbable copolymer and the amount of polymerized lactide is about 8 mole percent to about 12 mole percent of said absorbable copolymer.