Polycarbonate Sterilization Yellowing Stabilizer
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Solution Overview
Problem
Polycarbonate materials used in medical technology products undergo significant yellowing when irradiated for sterilization, which is not adequately addressed by existing stabilizer combinations, leading to high changes in the Yellowing Index even at standard radiation doses.
Innovation Solution
A thermoplastic composition comprising aromatic polycarbonate, polyether polyols, and a combination of thio compounds, specifically 3,3′-thiodipropionic acid, which acts as a stabilizer, reducing yellowing under various oxygen atmospheres during ionizing radiation sterilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ionizing radiation sterilization is applied to polycarbonate medical devices, then sterility is achieved, but yellowing of the material occurs due to degradation and rearrangement reactions
Solution Approach 1:
The patent introduces stabilizer combinations comprising polyether polyols and thio compounds (such as distearyl disulfide, pentaerythrityl tetrakis(3-laurylthiopropionate), and/or bis-(phenylsulfonyl)methane) as intermediary substances that mediate between the ionizing radiation and the polycarbonate material. These stabilizers act as sacrificial agents that absorb the harmful radiation energy and prevent it from causing degradation and yellowing of the polycarbonate, while still allowing the sterilization process to achieve the required sterility level.
Solution Approach 2:
The patent optimizes the concentration ratios and specific types of stabilizers in the combination to achieve maximum protection against yellowing. By carefully adjusting the parameters of the stabilizer formulation (specific combinations and amounts of polyether polyols and thio compounds), the patent finds the optimal balance between maintaining sterility through radiation exposure and minimizing yellowing through enhanced stabilization.
2Reliability
If radiation doses are increased to ensure complete sterilization, then sterility reliability improves, but yellowing of the polycarbonate material increases significantly
Solution Approach 1:
The patent applies stabilizer combinations before the sterilization process to cushion the polycarbonate material against the harmful effects of high radiation doses. The stabilizers are incorporated into the material formulation in advance, creating a protective system that is already in place before sterilization begins. This prior cushioning allows the material to withstand higher radiation doses needed for complete sterilization while minimizing yellowing through the stabilizers' protective action.
3Object-affected harmful factors
If stabilizers are added to reduce yellowing, then material appearance is preserved, but the complexity of the composition increases
Solution Approach 1:
The patent merges multiple stabilizing functions into a single coordinated system by combining polyether polyols and thio compounds in specific ratios. Rather than adding multiple separate stabilizers that would increase complexity, the patent creates a synergistic combination where the components work together to provide comprehensive protection against yellowing. This merging approach maintains relative composition simplicity while achieving effective yellowing reduction through the cooperative action of the stabilizer pair.
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
The composition significantly reduces yellowing after irradiation, maintaining a low Yellowing Index even under oxygen-free conditions, ensuring minimal discoloration and maintaining sterility in medical devices.
Implementation Method 1
When articles made from compositions based on aromatic polycarbonate are irradiated, yellowing of the polycarbonate materials occurs, which is stronger with increasing radiation dose
Implementation Method 2
yellowing of the polycarbonate materials occurs, which is stronger with increasing radiation dose, which is due to degradation and rearrangement reactions
Data Source
AI summary
The invention relates to a thermoplastic composition comprising A) aromatic polycarbonate, B) 0.1 to 5 wt.-% one or more polyether polyol(s) and C) one or more thermal stabilizer(s) selected from the group consisting of thio compounds excluding the following component D, characterized in that the composition additionally comprises D) 3,3′-thiodipropionic acid, wherein the total amount of components C plus D is 0.01 to 1.0 wt.-%. The invention also relates to medical technology products or parts of medical technology products consisting of such compositions as well as to a process for sterilization of such moulded parts by means of irradiation. The polycarbonate compositions according to the invention show significantly less yellowing after irradiation than known compositions.