Automotive Air Hose NBR Composition Heat Resistance
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Solution Overview
Problem
Conventional air hoses for automobiles, particularly PCV hoses, face limitations in heat resistance due to the use of butadiene-acrylonitrile copolymer rubber (NBR), which is not sufficiently resistant to high temperatures, and existing methods to enhance heat resistance, such as using hydrogenated NBR or specific vulcanization accelerators, do not provide sufficient improvements at a low cost.
Innovation Solution
A two-layered air hose structure with an inner tube made of an NBR composition that includes a specific blend of thiuram compounds, 4,4′-dithio dimorpholine, and thiazole compounds as vulcanization accelerators, along with a plasticizer of molecular weight 700 to 2000, to enhance heat resistance and maintain elongation properties, while keeping costs low.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional NBR is used for the inner tube, then the air hose can be manufactured at low cost, but the heat resistance is insufficient
Solution Approach 1:
The patent changes the chemical parameters of NBR by controlling the acrylonitrile content (30-50 mass%) and Mooney viscosity (50-90), and optimizes vulcanization parameters including accelerator ratios and curing conditions to achieve sufficient heat resistance while maintaining cost-effectiveness
Solution Approach 2:
The patent creates a composite vulcanization system combining multiple accelerators (thiuram compound, 4,4'-dithio dimorpholine, and thiazole compound) with specific ratios to achieve synergistic effects that improve heat resistance beyond what single accelerators can provide
2Temperature
If HNBR is used instead of NBR, then heat resistance is improved, but the manufacturing cost increases
Solution Approach 1:
The patent modifies NBR parameters (acrylonitrile content, viscosity) and vulcanization conditions to achieve heat resistance comparable to HNBR while maintaining the lower cost advantage of NBR material
Solution Approach 2:
The patent uses cost-effective NBR material with optimized vulcanization rather than expensive HNBR, achieving acceptable heat resistance at lower material cost
3Productivity
If dibenzothiazyl disulfide or tetramethylthiuram monosulfide is used as vulcanization accelerator, then vulcanization speed is improved, but sufficient heat resistance is not achieved
Solution Approach 1:
The patent combines multiple vulcanization accelerators (thiuram compound, 4,4'-dithio dimorpholine, and thiazole compound) in specific ratios to achieve both fast vulcanization speed and sufficient heat resistance that single accelerators cannot provide
Solution Approach 2:
The patent creates a composite accelerator system where different accelerator compounds work synergistically to simultaneously improve vulcanization kinetics and thermal stability
4Temperature
If the air hose is exposed to high temperature, then the elongation decreases and hardness increases, but the structural integrity must be maintained
Solution Approach 1:
The patent optimizes NBR composition parameters (acrylonitrile content, viscosity) and vulcanization parameters to achieve heat resistance while limiting elongation decrease and hardness increase within acceptable ranges after heat aging
Solution Approach 2:
The patent uses a two-layer structure with NBR inner tube and CSM outer cover, where each layer is optimized for its specific function and requirements
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 significantly improves the heat resistance of the air hose, suppressing the decrease in elongation and increase in hardness due to heat, meeting high heat aging test standards at 120°C for 20 days with hardness HS of 90 or less and elongation at break EB of 140% or more.
Implementation Method 1
an unvulcanized NBR is vulcanized in the presence of 0.5 to 7.0 parts by mass of a thiuram compound serving as a vulcanization accelerator, 0 to 2.5 parts by mass of 4,4'-dithio dimorpholine, and 2.0 to 7.0 parts by mass of a thiazole compound
Implementation Method 2
5 to 50 parts by mass of a plasticizer having a molecular weight of 700 to 2,000 is blended to 100 parts by mass of the unvulcanized NBR
Data Source
AI summary
An air hose for an automobile, which has a two-layered structure of an inner tube made of an NBR composition and an outer cover made of a CSM composition, wherein the NBR composition satisfies (A) and (B) below: (A) an unvulcanized NBR in which an amount of AN is 30 to 50 and a Mooney viscosity (ML (1+4) 100° C.) is 50 to 90, is vulcanized in the presence of 0.5 to 7.0 parts by mass of a thiuram compound serving as a vulcanization accelerator, 0 to 2.5 parts by mass of 4,4′-dithio dimorpholine, and 2.0 to 7.0 parts by mass of a thiazole compound to 100 parts by mass of the unvulcanized NBR; and (B) 5 to 50 parts by mass of a plasticizer having a molecular weight of 700 to 2,000 is blended to 100 parts by mass of the unvulcanized NBR.