Nitrile Rubber Composition for Oil and Cold Resistance
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Solution Overview
Problem
Nitrile group-containing highly saturated copolymer rubber exhibits insufficient cold resistance, compression set resistance, resistance to swelling in oil, and resistance to hardening in oil, particularly when immersed in fuels containing condensed polycyclic aromatic compounds.
Innovation Solution
A nitrile rubber composition is developed by mixing a filler in the range of 50 to 90 parts by weight with an adipic acid ester-based plasticizer and/or an ether ester-based plasticizer, along with a nitrile group-containing highly saturated copolymer rubber having an α,β-ethylenically unsaturated nitrile monomer unit content of 14 wt% to 20.5 wt% and an iodine value of 120 or less, to enhance the cross-linked rubber's properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitrile group-containing highly saturated copolymer rubber is used, then heat resistance and oil resistance are improved, but cold resistance deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters of the rubber by controlling the nitrile monomer content (14-20.5 wt%) and iodine value (120 or less), and by adding specific plasticizers (adipic acid ester-based and/or ether ester-based) in controlled amounts (5-27.5 parts by weight per 100 parts rubber). This compositional adjustment resolves the contradiction between heat/oil resistance and cold resistance.
Solution Approach 2:
The invention creates a composite rubber composition by combining the nitrile group-containing highly saturated copolymer rubber with fillers (50-90 parts by weight per 100 parts rubber) and specific plasticizers. This composite approach allows the material to simultaneously achieve heat resistance, oil resistance, and improved cold resistance.
2Reliability
If the nitrile group-containing highly saturated copolymer rubber is cross-linked, then compression set resistance is improved, but resistance to swelling in oil deteriorates
Solution Approach 1:
The invention optimizes the cross-linking parameters and rubber composition parameters, specifically controlling the nitrile monomer content (14-20.5 wt%) and iodine value (120 or less), to achieve a balance where the cross-linked structure provides compression set resistance while the controlled unsaturation level prevents excessive swelling in oil.
3Strength
If the cross-linked rubber is immersed in fuel oil containing condensed polycyclic aromatic compounds, then hardness increase occurs, but cold resistance deteriorates
Solution Approach 1:
The invention changes the rubber's chemical composition parameters, specifically controlling the nitrile monomer content (14-20.5 wt%) and adding specific plasticizers (adipic acid ester-based and/or ether ester-based in 5-27.5 parts by weight per 100 parts rubber), to reduce the rubber's affinity for condensed polycyclic aromatic compounds. This prevents excessive hardness increase and cold resistance deterioration when immersed in such fuels.
Data Source
AI summary
The present invention provides a nitrile rubber composition comprising a filler (B) in a content of 50 to 90 parts by weight and an adipic acid ester-based plasticizer and/or an ether ester-based plasticizer (C) in a content of 0 to 29.9 parts by weight in relation to 100 parts by weight of a nitrile group-containing highly saturated copolymer rubber (A) comprising an α,β-ethylenically unsaturated nitrile monomer unit in an proportion of 14 wt% or more and less than 21 wt%, and having an iodine value of 120 or less.