Thermoplastic Elastomer Seal Cap for Prefilled Syringe
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Solution Overview
Problem
Existing seal caps for prefilled syringes made of cyclic polyolefin barrels tend to stick to the barrel after high-pressure steam sterilization and storage, compromising their autoclave sterilization performance and durability.
Innovation Solution
A seal cap formed from a thermoplastic elastomer composition, primarily consisting of a mixture of styrene-based thermoplastic elastomer and hydrocarbon-based rubber softener, which prevents sticking to the cyclic polyolefin barrel and maintains satisfactory autoclave sterilization performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a seal cap is mounted on a cyclic polyolefin barrel and subjected to high-pressure steam sterilization, then sterilization is achieved, but the seal cap sticks to the barrel after sterilization and storage
Solution Approach 1:
The seal cap is constructed from a composite material system consisting of a thermoplastic elastomer base resin combined with a specific lubricant. This composite formulation creates a surface composition that prevents adhesion to the cyclic polyolefin barrel while maintaining the structural integrity and sterilization resistance required for medical applications.
Solution Approach 2:
The invention modifies the surface properties of the seal cap by controlling the lubricant content (0.1-10 parts by weight per 100 parts of base resin) and its molecular structure (kinematic viscosity at 100°C). These parameter changes create an low-energy surface that repels the cyclic polyolefin barrel material, preventing sticking without compromising sterilization performance.
2Ease of operation
If the seal cap is made from conventional elastic rubber material to seal the needle tip, then sealing function is achieved, but the material deteriorates upon ozone exposure and sticks to the barrel
Solution Approach 1:
The invention transitions from conventional crosslinked rubber to a thermoplastic elastomer system with specific compositional parameters. The base resin selection (styrene-based, olefin-based, or polyester-based) and lubricant formulation create a material with inherent ozone resistance and low surface energy, eliminating both deterioration and sticking issues while preserving sealing capability.
Solution Approach 2:
The thermoplastic elastomer is combined with a specifically selected lubricant (paraffinic oil, naphthenic oil, or ester) to create a composite material that simultaneously provides sealing function, ozone resistance, and anti-sticking properties. The synergistic interaction between the base resin and lubricant achieves all required functions without the drawbacks of conventional rubber materials.
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 solution ensures the seal cap does not adhere to the barrel after sterilization or storage, maintaining effective sterilization capabilities and resisting ozone exposure, thus preventing premature deterioration.
Implementation Method 1
a seal cap (3) formed of a thermoplastic elastomer composition containing as a main component a mixture of a styrene-based thermoplastic elastomer and a softener for hydrocarbon-based rubber... the seal cap does not stick to the barrel
Data Source
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AI summary
An assembly (10) of the present invention for a syringe is composed of a barrel (2), made of cyclic polyolefin, which has a barrel body (21) having a distal end part (22) and a piercing needle (6) which has a piercing needle tip (61) at its distal end and is fixed to a piercing needle fixing portion of the barrel and a seal cap (3) mounted on the barrel (2). The seal cap (3) is formed of a thermoplastic elastomer composition containing as its main component a mixture of a styrene-based thermoplastic elastomer and a softener, for hydrocarbon-based rubber, which has a kinematic viscosity of 1 to 5,000mm2s-1 at 100 degrees C and a naphthenic carbon ratio (%CN) of not more than 20% when said naphthenic carbon ratio is measured by ring analysis.