Hydrogenated Block Copolymer Sterilization pH Stability
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Solution Overview
Problem
The sterilization of medical formed articles using high-energy rays can cause a significant change in pH due to elution in water, leading to potential contamination and quality issues.
Innovation Solution
A method involving a resin composition of a hydrogenated block copolymer with a specific hydrogenation rate and a phenol-based antioxidant, applied in a specific ratio, is used to suppress pH changes during high-energy ray sterilization. This composition includes a block copolymer with aromatic and linear conjugated diene units, and the antioxidant is added in a calculated amount to prevent oxidation and maintain transparency and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-energy rays are applied to sterilize medical formed articles made of hydrogenated block copolymer, then sterilization is achieved, but pH change due to elution occurs
Solution Approach 1:
The patent applies preliminary action by adding a phenol-based antioxidant to the resin composition before sterilization. This antioxidant pre-protection mechanism suppresses oxidative degradation that would otherwise be triggered by high-energy ray exposure, thereby preventing pH change due to elution while maintaining sterilization effectiveness
Solution Approach 2:
The phenol-based antioxidant acts as an intermediary substance between the high-energy rays and the hydrogenated block copolymer. It absorbs the harmful oxidative effects of the sterilization process, protecting the polymer structure from degradation and preventing subsequent pH changes during elution
2Strength
If antioxidant is added to prevent oxidative degradation during forming, then coloration and strength decrease are prevented, but pH change due to elution occurs during sterilization
Solution Approach 1:
The patent applies parameter changes by specifically selecting a phenol-based antioxidant and controlling its content within 0.01-0.50 parts by mass per 100 parts of hydrogenated block copolymer. This optimized parameter range provides sufficient protection during both forming and sterilization processes, preventing pH change while maintaining mechanical strength
3Object-affected harmful factors
If phenol-based antioxidant is used to suppress pH change during sterilization, then elution is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines a specific parameter range for phenol-based antioxidant content (0.01-0.50 parts by mass per 100 parts of polymer) that balances pH change suppression with manufacturing feasibility. This quantified range provides clear manufacturing guidance while achieving the desired sterilization resistance
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 method effectively suppresses pH changes during sterilization, maintaining the integrity and quality of the medical formed articles by preventing oxidative degradation and elution, ensuring excellent heat resistance and content visibility.
Implementation Method 1
applying high-energy rays to a medical formed article
Implementation Method 2
sterilizing a medical formed article by applying high-energy rays
Implementation Method 3
prevent coloration and a decrease in strength due to oxidative degradation
Implementation Method 4
mix an antioxidant (e.g., phenol-based antioxidant, phosphorus-based antioxidant, or sulfur-based antioxidant) with a hydrogenated block copolymer
Implementation Method 5
a hydrogenated block copolymer that exhibits excellent transparency, heat resistance, flexibility
Data Source
AI summary
A method for producing a sterilized medical formed article comprising applying high-energy rays to a medical formed article at an exposure E, the medical formed article being formed of a resin composition that comprises a hydrogenated block copolymer and a phenol-based antioxidant, the hydrogenated block copolymer being obtained by hydrogenating 99% or more of unsaturated bonds of a block copolymer that comprises at least two polymer blocks [A] and at least one polymer block [B], the polymer block [A] comprising a repeating unit derived from an aromatic vinyl compound as a main component, the polymer block [B] comprising a repeating unit derived from a linear conjugated diene compound as a main component, and a ratio (wA:wB) of a weight fraction wA of the polymer block [A] to a weight fraction wB of the polymer block [B] being 30:70 to 70:30, and the resin composition comprising the phenol-based antioxidant in a ratio of W to 0.50 parts by weight based on 100 parts by weight of the hydrogenated block copolymer, W being calculated by an expression (1): W=0.46×100−H+0.04×E/25, where, W is the ratio (parts by weight) of the antioxidant based on 100 parts by weight of the hydrogenated block copolymer, H is the hydrogenation rate (%) of the hydrogenated block copolymer, H is a numerical value from 99 to 100, and E is the exposure (kGy) of the high-energy rays.