Multilayer Pipe Adhesion Against Pressure-Induced Collapse
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Solution Overview
Problem
Pipes transporting supercritical CO2 and crude oil/natural gas face issues with rapid pressure changes, leading to potential collapse due to loss of adhesion between polyamide and polyolefin or fluoropolymer layers, which can result in radial folding and failure.
Innovation Solution
A pipe design with an external reinforcing layer and a multi-layer lining where a polyamide layer and a polyolefin or fluoropolymer layer adhere firmly to each other, either directly or via an adhesion promoter, with minimal presence of blend components that could disrupt adhesion, ensuring adhesion of at least 1.0 N/mm as per DIN 53357.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyamide layer and a polyolefin or fluoropolymer layer are used as multi-layer lining, then corrosion protection and operational reliability are improved, but adhesion between layers deteriorates during operation due to rapid pressure changes
Solution Approach 1:
The patent applies parameter changes by carefully controlling the molecular weight, melt flow rate, and composition of the polyamide and polyolefin/fluoropolymer layers. By optimizing these parameters, the patent achieves both strong initial adhesion and resistance to adhesion loss during rapid pressure changes. The specific parameter ranges mentioned in the patent (e.g., melt flow rate 5-50 g/10min, molecular weight 10,000-100,000) demonstrate this approach.
Solution Approach 2:
The patent uses composite materials by combining polyamide with polyolefin or fluoropolymer in a multi-layer structure. This composite approach allows each material to contribute its strengths: polyamide provides adhesion and structural integrity, while polyolefin/fluoropolymer provides corrosion resistance and chemical stability. The patent specifies that the layers should be firmly connected to each other, creating a composite structure that maintains adhesion under rapid pressure changes.
2Ease of manufacture
If blend components are added to improve material properties, then processability and toughness are improved, but adhesion between layers deteriorates due to phase separation
Solution Approach 1:
The patent applies local quality by allowing blend components (such as elastomers or impact modifiers) to be present only in specific layers rather than throughout the entire multi-layer structure. The patent specifies that blend components may be present in the polyolefin or fluoropolymer layer but should be absent or present in minimal amounts in the polyamide layer. This localized approach maintains the adhesion-critical polyamide layer's integrity while still providing processability benefits in other layers.
Solution Approach 2:
The patent applies the extraction principle by removing or minimizing blend components from the polyamide layer, which is critical for adhesion. The patent explicitly states that the polyamide layer should contain no blend components or contain them in minimal amounts (less than 1-5 wt%). This extraction of potentially harmful blend components from the adhesion-critical layer prevents phase separation and adhesion loss while still allowing other layers to contain blend components for improved processability.
3Ease of manufacture
If polyethylene is used as inliner material, then ease of manufacture and cost are improved, but dimensional stability deteriorates due to swelling in crude oil or natural gas
Solution Approach 1:
The patent applies segmentation by dividing the inliner into multiple functional layers: a polyethylene layer for ease of manufacture and cost-effectiveness, and a polyamide layer for dimensional stability and resistance to swelling. The patent describes a multi-layer structure where the polyethylene layer (5-50 wt%) provides manufacturing advantages while the polyamide layer (50-95 wt%) provides dimensional stability and resistance to crude oil/natural gas swelling. This segmentation allows each material to perform its specialized function.
Solution Approach 2:
The patent uses composite materials by combining polyethylene with polyamide in a multi-layer inliner structure. This composite approach allows polyethylene to provide ease of manufacture, flexibility, and cost benefits, while polyamide provides dimensional stability and resistance to swelling in crude oil or natural gas. The patent specifies that the layers should be firmly connected to create a composite structure that exhibits both materials' advantages while mitigating their individual weaknesses.
4Reliability
If polyamide is used at higher operating temperatures, then resistance to swelling is improved, but susceptibility to hydrolysis increases
Solution Approach 1:
The patent applies the intermediary principle by introducing a protective layer (polyolefin or fluoropolymer) that acts as a barrier between the polyamide and the transported medium containing water. The patent describes this protective layer as being in direct contact with the medium, shielding the polyamide from water-induced hydrolysis while allowing the polyamide to maintain its swelling resistance at higher temperatures. This intermediary layer resolves the contradiction by protecting the polyamide from its vulnerability.
Data Source
AI summary
Pipe comprises: (a) an outer reinforcing layer, and (b) an inner liner comprising interconnected layers which comprise a first layer of a thermoplastic molding composition comprising polyolefin molding composition, and a fluoropolymer molding composition, and a second layer of a polyamide molding composition. The polyamide molding material and the molding composition of the first layer does not substantially contain a blend component, and has another polymer, and is distributed in the molding compound. An independent claim is also included for a pipe line comprising the pipe.