Bioresorbable Polymer Moisture Control for Extrusion
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Solution Overview
Problem
The challenge in manufacturing biodegradable polymeric stents lies in achieving the right balance of mechanical properties and degradation behavior, which is sensitive to the properties of the biodegradable polymer, particularly in maintaining radial strength and controlling moisture content during the extrusion process to prevent molecular weight loss and monomer generation.
Innovation Solution
A method involving the use of a biodegradable polymer resin with controlled moisture content, achieved by passing a drying gas through the resin prior to extrusion, maintaining the moisture level between 50 ppm and 1000 ppm, and adjusting temperature and flow rate to ensure consistent processing conditions, thereby reducing molecular weight loss and monomer generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the polymer resin is dried to very low moisture content (less than 50 ppm) before extrusion, then molecular weight loss is reduced, but the resin becomes difficult to process due to increased melt viscosity
Solution Approach 1:
The patent applies parameter changes by precisely controlling the moisture content of polymer resin within a specific range (50-1000 ppm) rather than using extreme drying conditions. This optimized parameter range resolves the contradiction by maintaining low enough moisture to prevent excessive molecular weight loss during extrusion, while retaining sufficient moisture to keep melt viscosity at processable levels.
2Manufacturing precision
If the polymer resin is dried to very low moisture content (less than 50 ppm) before extrusion, then monomer generation is reduced, but processing conditions become harder to maintain
Solution Approach 1:
The patent establishes a specific moisture content range (50-1000 ppm) that simultaneously achieves low monomer generation and facilitates processing. This parameter optimization reduces the need for complex processing control systems, as the resin within this range processes more reliably compared to extremely dry resin.
3Ease of manufacture
If higher moisture content is allowed in the polymer resin during extrusion, then processing becomes easier, but molecular weight loss and monomer generation increase
Solution Approach 1:
The patent identifies and implements an optimized moisture content range (50-1000 ppm) that balances processability with molecular weight preservation. This parameter control ensures the resin remains easy to process while preventing excessive hydrolysis that would cause molecular weight loss and monomer generation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures the production of stents with consistent mechanical properties and controlled degradation profiles, maintaining radial strength for an adequate period while minimizing premature absorption and ensuring the stent's structural integrity during its clinical use.
Implementation Method 1
passing a drying gas through the polymer resin during the extrusion process prior to being fed into the extruder to remove moisture from the polymer resin
Implementation Method 2
passing a gas containing dry carbon dioxide through the polymer resin prior to entering the extruder during the extrusion process, wherein the polymer resin absorbs some of the carbon dioxide which reduces melt viscosity of the polymer resin
Data Source
AI summary
Methods and systems for controlling the moisture content of biodegradable and bioresorbable polymer resin during extrusion above a lower limit that allows for plasticization of the polymer resin melt and below an upper limit to reduce or prevent molecular weight loss are disclosed. Methods are further disclosed involving plasticization of a polymer resin for feeding into an extruder with carbon dioxide and freon.