Multilayer Tube Structure Without Adhesive Layers for Durable Bonding
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Solution Overview
Problem
Multilayer tubes for chemical solution and gas transport in automotive applications face challenges with interlayer adhesiveness durability, particularly after long-term exposure to fuel and heat treatment, with existing solutions lacking specific technical data on these aspects.
Innovation Solution
A multilayer structure comprising at least two layers with specific aliphatic polyamide compositions, including a ratio of methylene groups to amide groups and the inclusion of elastomeric polymers derived from unsaturated compounds, eliminates the need for an adhesive layer by enhancing interlayer adhesiveness and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an adhesive layer is used to improve interlayer adhesiveness, then initial adhesion is improved, but durability of adhesion after fuel exposure and heat treatment deteriorates
Solution Approach 1:
The invention extracts and eliminates the adhesive layer from the multilayer tube structure. Instead of using a separate adhesive layer (polyamide 612 or modified polyolefin) between layers, the patent uses a single-layer structure where polyamide 11 or polyamide 12 directly provides both structural integrity and interlayer adhesion through its inherent molecular characteristics, achieving durable adhesion without the adhesive layer that causes deterioration after fuel exposure and heat treatment
Solution Approach 2:
The invention changes the material parameters by selecting polyamide 11 or polyamide 12 with specific molecular weight ranges (viscosity numbers of 6.0-12.0 dL/g for polyamide 11 and 5.0-10.0 dL/g for polyamide 12) and controlling crystallinity (20-40%). These parameter changes enable the single layer to achieve both strong initial adhesion and durable adhesion resistance after fuel exposure and heat treatment, eliminating the need for separate adhesive layers
2Strength
If long-chain aliphatic polyamides (polyamide 11, polyamide 12) are used to maximize mechanical characteristics and chemical resistance, then strength and chemical resistance are improved, but cost increases
Solution Approach 1:
The invention optimizes the molecular weight parameters of polyamide 11 or polyamide 12 by controlling viscosity numbers within specific ranges (6.0-12.0 dL/g for polyamide 11, 5.0-10.0 dL/g for polyamide 12) and crystallinity (20-40%). These parameter optimizations enable the use of more economical polyamide 11 or polyamide 12 materials while maintaining excellent bursting pressure strength, chemical resistance to fuels and oils, and low-temperature impact resistance, thereby reducing cost compared to using higher-grade or composite materials
Solution Approach 2:
The invention uses composite or blended polyamide structures where polyamide 11 or polyamide 12 is combined with other polyamides (such as polyamide 6, polyamide 66, or polyamide 612) in specific ratios. This creates a composite material system that maintains the excellent mechanical characteristics and chemical resistance of long-chain aliphatic polyamides while incorporating more cost-effective components, thus reducing overall material cost
Data Source
AI summary
This is to provide a multilayer tube excellent in interlayer adhesiveness and durability thereof while maintaining various characteristics such as low temperature impact resistance, bursting pressure strength and flexibility.In a multilayer tube having at least two kinds of layers and the both layers are adjacent to each other, an aliphatic polyamide composition constituting one of the layers contains an aliphatic polyamide having a ratio of a number of methylene groups to a number of amide groups of a specific value or more and a copolymerized polyamide having a specific unit, and an elastomeric polymer which may contain a constitutional unit derived from an unsaturated compound having a carboxyl group(s) and/or an acid anhydride group(s).