Soft Elastomeric Films via Selective Hydrogenation
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Solution Overview
Problem
Soft elastomeric films used in personal hygiene articles, such as gloves and diapers, face challenges with thermal, oxidative, and UV degradation due to their unsaturated nature, limiting their stability and performance over time.
Innovation Solution
Development of selectively hydrogenated block copolymers with specific molecular weights and vinyl content, combined with coupling agents and hydrogenation processes, to create stable and soft elastomeric films that retain strength and elasticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If unsaturated block copolymers (SIS) are used to produce soft elastomeric films, then softness and strength are achieved, but thermal, oxidative and UV stability deteriorate
Solution Approach 1:
The patent applies parameter changes by partially hydrogenating the unsaturated block copolymer to reduce double bond content from 100% (in SIS) to a controlled level (0-50% retention), thereby improving oxidative and UV stability while maintaining sufficient softness and strength for personal hygiene applications
Solution Approach 2:
The patent creates a composite material system by combining hydrogenated block copolymer with specific additives including antioxidants, UV absorbers, and processing aids, forming a stable elastomeric film composition that addresses multiple performance requirements simultaneously
2Reliability
If saturated block copolymers (SEBS) are used to improve stability, then thermal and oxidative stability improve, but softness and strength deteriorate
Solution Approach 1:
The patent applies partial action by performing partial hydrogenation rather than complete hydrogenation, retaining 0-50% of double bonds to maintain the elastomeric properties and softness characteristic of unsaturated polymers while gaining sufficient stability for commercial applications
Solution Approach 2:
The patent modifies the saturation level parameter to an intermediate state (partially hydrogenated) that balances the conflicting requirements of stability and softness, avoiding the extremes of fully unsaturated (unstable) or fully saturated (too rigid) states
3Productivity
If high temperatures are used during melt processing, then processing efficiency improves, but thermal degradation of unsaturated films worsens
Solution Approach 1:
The patent applies preliminary action by pre-hydrogenating the block copolymer before processing, which stabilizes the material against thermal degradation during subsequent melt processing operations, allowing for more robust processing conditions
Solution Approach 2:
The patent changes the chemical composition parameter (double bond content) to reduce susceptibility to thermal degradation, enabling processing at temperatures and shear rates that would otherwise cause degradation of fully unsaturated polymers
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 resulting films exhibit improved thermal, oxidative, and UV stability while maintaining softness and strength, suitable for prolonged use in personal hygiene applications.
Implementation Method 1
selectively hydrogenated block copolymers which has the softness of conventional SIS-based films but the stability inherent in saturated conjugated diene rubbers
Data Source
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AI summary
Elastomeric films which are both soft and thermally, UV and oxidatively stable are provided. The films are composed of coupled, selectively hydrogenated block copolymers having a relatively high molecular weight and high vinyl content. In addition to the block copolymer other components may be present in formulated films such as other block copolymers, hydrocarbon resins, polyolefins, metallocene polyolefins, homopolystyrene or mineral oils. The softness of the films is determined by the stress at 100% tensile elongation where the films with suitable softness have a 100% stress of about 100 psi or less. While soft, the films also are strong with tensile strengths of 1000 psi or more and suitable hysteresis properties. The elastomeric films are useful as integral components of personal hygiene articles such as gloves, diapers, incontinence products, disposable swimwear and disposable undergarments.