Polycarbonate Sterilization Stabilizer Composition

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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 suboptimal sterilization results and processability issues.

Innovation Solution

A thermoplastic composition comprising aromatic polycarbonate, polyether polyols, and 3,3′-thiodipropionic acid, which effectively stabilizes the material against ionizing radiation-induced yellowing, even in oxygen-free atmospheres, while maintaining processability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polycarbonate materials are irradiated for sterilization, then sterility is achieved, but significant yellowing occurs

Engineering Contradiction:

ImprovesterilityVSAvoidyellowing

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a stabilizer combination comprising polyether polyols and sulfur-containing additives as intermediary substances that mediate between the irradiation process and the polycarbonate material. These stabilizers act as protective intermediaries that absorb radiation-induced stress and prevent direct harmful effects on the polycarbonate chains, thereby reducing yellowing while allowing sterilization to proceed effectively.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a composite stabilizer system combining multiple components: polyether polyols (providing bulk stabilization) and sulfur-containing additives (providing radical scavenging and yellowing prevention). This composite approach creates a synergistic protective effect that is greater than individual stabilizers alone, effectively addressing the yellowing issue while maintaining sterilization efficacy.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If stabilizers are added to reduce yellowing, then appearance is improved, but processability may be affected

Engineering Contradiction:

ImproveyellowingVSAvoidprocessability

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent optimizes the concentration parameters of the stabilizers within specific ranges: polyether polyols at 0.1-5 wt.% and sulfur-containing additives at 0.01-0.30 wt.%. By carefully controlling these parameter values, the patent achieves effective yellowing prevention while maintaining the material's processability and avoiding negative impacts on injection molding or extrusion operations.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If radiation dose is increased to ensure sterility, then sterility is improved, but yellowing increases

Engineering Contradiction:

ImprovesterilityVSAvoidyellowing

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of radiation-induced yellowing into a beneficial outcome by using the radiation process itself to activate or enhance the stabilizer mechanism. The sulfur-containing additives and polyether polyols work synergistically with the radiation field to protect the polycarbonate structure, transforming what would be pure harm into a controlled process that achieves both sterilization and color stability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 combination significantly reduces yellowing after irradiation, ensuring high sterility and maintaining the material's properties, allowing for efficient sterilization of medical devices without compromising their appearance or functionality.

Implementation Method 1

sterilization by means of radiation allows a sterilization of medical technology products in their closed packaging

Methodology Applied

Scientific EffectIonizing radiation: Radiation

Implementation Method 2

the yellowing directly after irradiation partly recedes with relaxation of the sample

Methodology Applied

Scientific EffectStabilization against radiation-induced degradation:

Data Source

PatentUS11680164B2By means of ionizing radiation sterilizable moulded parts made from polycarbonate

Publication Date: 2023.06.20 COVESTRO DEUTSCHLAND AG

AI summary

The invention relates to a thermoplastic composition comprising A) aromatic polycarbonate, B) 0.1 to 5 wt.-% one or more polyether polyols and C) 0.01 to 0.30 wt.-% 3,3′-thiodipropionic acid. 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 and still have good mechanical properties.