EVOH Multilayer Pipe Resin Composition Oxidation Resistance
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Solution Overview
Problem
Multilayered pipes used in hot water circulation systems, particularly those with EVOH layers, face issues with oxidation degradation at high temperatures, leading to cracks and loss of gas barrier properties, which affects the longevity and performance of the pipes, especially under the constraints of limited installation space in Japanese homes where bending radii are smaller.
Innovation Solution
A resin composition containing 0.001 to 5 parts by mass of an antioxidant and 0.00001 to 0.3 parts by mass of a conjugated polyene compound, such as sorbic acid, is used with ethylene-vinyl alcohol copolymer (EVOH) to inhibit oxidation degradation and maintain mechanical strength, with the EVOH layer being the outermost layer to prevent exposure to oxygen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EVOH layer is used as outermost layer to provide excellent oxygen barrier property, then gas barrier property is improved, but oxidation degradation occurs at high temperatures leading to cracks and loss of mechanical strength
Solution Approach 1:
The patent applies preliminary action by incorporating antioxidants and conjugated polyene compounds into the EVOH resin composition before the pipe is installed and used. These additives pre-establish protection against oxidation degradation, enabling the EVOH layer to maintain its mechanical strength and gas barrier properties even when exposed to high temperatures and oxygen over long periods.
Solution Approach 2:
The patent uses antioxidants and conjugated polyene compounds as intermediary substances that mediate between the EVOH layer and the harmful oxidative environment. These intermediaries scavenge free radicals and inhibit oxidation reactions, protecting the EVOH polymer chains from degradation while allowing the layer to maintain its oxygen barrier function.
2Reliability
If EVOH layer is exposed to high temperatures for long periods, then oxygen barrier property is maintained, but oxidation degradation accelerates causing cracks parallel to the lengthwise direction
Solution Approach 1:
The patent incorporates antioxidants and conjugated polyene compounds into the EVOH resin composition before use, establishing preliminary protection against temperature-accelerated oxidation. These additives are positioned in advance to counteract the increased oxidation rate that occurs at elevated temperatures, preventing crack formation while maintaining barrier properties.
Solution Approach 2:
The patent changes the chemical composition parameters of the EVOH layer by adding specific antioxidants (0.001-5 parts by mass) and conjugated polyene compounds (0.00001-0.3 parts by mass). This parameter modification enables the material to resist oxidation degradation at high temperatures without compromising its oxygen barrier performance.
3Adaptability or versatility
If secondary processing is performed to bend the pipe with small bending radius, then adaptability to installation space is improved, but cracking occurs in direction perpendicular to the lengthwise direction of EVOH layer
Solution Approach 1:
The patent applies preliminary action by incorporating antioxidants and conjugated polyene compounds into the EVOH resin composition before the pipe undergoes secondary processing. This pre-established protection ensures that the EVOH layer maintains sufficient mechanical strength and flexibility to withstand bending with small radii without developing cracks perpendicular to its lengthwise direction.
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 resin composition significantly reduces cracking in EVOH layers due to oxidation degradation, maintaining excellent gas barrier properties and mechanical strength even at high temperatures, thereby extending the lifespan of the pipes and improving handling and insulation performance.
Implementation Method 1
the exposure of the EVOH layer to remarkably high temperatures for a long period of time gradually accelerates oxidation degradation of EVOH due to the oxygen present in the air
Implementation Method 2
The addition of an antioxidant is effective against the oxidation degradation of EVOH in the air
Implementation Method 3
a multilayered pipe using an ethylene-vinyl alcohol copolymer (hereinafter, may be abbreviated as EVOH) is confirmed to have the highest oxygen barrier property
Data Source
AI summary
An object of the present invention is to provide a multilayered pipe having a layer comprising a resin composition containing EVOH, which is unlikely to exhibit the occurrence of cracking in the EVOH layer due to oxidative degeneration and has excellent gas barrier property even during long-term usage at high temperatures, and also to provide a resin composition for obtaining the multilayered pipe. The present invention relates to a resin composition containing 0.001 to 5 parts by mass of an antioxidant (B) and 0.00001 to 0.3 parts by mass of a conjugated polyene compound (C) having a molecular weight of 1000 or less, relative to 100 parts by mass of an ethylene-vinyl alcohol copolymer (A).