Within the last ten years or so, synthetic absorbable polymers have become widely used in surgical practice. The principal utility has been in sutures. However, shaped articles other than sutures are also beginning to become important in medical/surgical procedures. For instance, ligating clips, staples, other fastening devices, temporary support members, and the like are beginning to be fabricated from synthetic absorbable polymers so that such articles can be employed during a surgical procedure, implanted in the body to perform a function, and then will gradually be absorbed in the body after the device is no longer needed.
An important class of synthetic absorbable polymers that are starting to be employed to make absorbable shaped articles are polydioxanones. Typically, the shaped articles made from these polymers are injection molded by procedures that are analogous to well known injection molding techniques. One characteristic of polydioxanone polymers that has tended to limit production rates and has thus tended to increase the cost of shaped articles made from them, is that after the polymer has been injected into a mold, and the mold has been cooled in accordance with conventional injection molding techniques, the polymer can be very slow to crystallize. Sometimes, the polymer will tend to cool to a temperature well below its optimal crystallization temperature without solidifying. As a result, the molding cycles employed in the production of shaped articles from these polymers tend to be much slower than would be desirable.
The present invention is directed to a means for increasing the rate of solidification of polydioxanone by crystallization in a molding process utilizing said polymer.
USPTO Backgrounds
USPTO Backgrounds