Tire Rubber Composition for Stable Complex Modulus Over Time
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Solution Overview
Problem
Conventional rubber compositions for tires experience an increase in complex modulus E* over time, leading to a decrease in wet grip performance, indicating a need for reduced changes in complex modulus E* over time.
Innovation Solution
The development of rubber compositions containing a copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound, with a heat aging resistance index of 27 or less, incorporating hydrogenated styrene-butadiene rubber and silica, and specific softeners to maintain stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional rubber compositions are used, then abrasion resistance is improved, but complex modulus E* increases over time leading to decreased wet grip performance
Solution Approach 1:
The patent changes the chemical composition parameters of the rubber by incorporating hydrogenated styrene-butadiene rubber with specific molecular weight (200,000 to 2,000,000) and degree of hydrogenation (60 mol% or more), along with controlling the A value between rubber and softener to less than 4.5. This parameter optimization resolves the contradiction by maintaining stable complex modulus over time while preserving abrasion resistance.
Solution Approach 2:
The patent creates a composite rubber composition combining hydrogenated styrene-butadiene rubber with specific softeners where the A value is less than 4.5. This composite structure achieves both improved abrasion resistance and maintained wet grip performance by preventing excessive crosslinking while ensuring good interfacial compatibility between rubber and softener phases.
2Strength
If rubber composition is optimized for initial performance, then complex modulus E* increases during service, but this leads to performance degradation over time
Solution Approach 1:
The patent applies beforehand cushioning by pre-selecting rubber and softener combinations with A value less than 4.5, which creates a stable formulation that resists excessive crosslinking during service. This preliminary optimization of composition parameters cushions against the natural tendency of rubber to harden over time, maintaining wet grip performance throughout the service life.
3Stability of the object's composition
If hydrogenated styrene-butadiene rubber with high degree of hydrogenation is used, then stability is improved, but compatibility with softener may be reduced
Solution Approach 1:
The patent optimizes the parameter A (calculated from Hansen solubility parameters) to be less than 4.5, which balances the degree of hydrogenation (60 mol% or more) with softener compatibility. This parameter control ensures that the rubber composition achieves both compositional stability and adequate compatibility with softeners for processing and performance.
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 rubber compositions effectively reduce changes in complex modulus E* over time, maintaining good tire performance, including wet grip, for an extended period, as demonstrated by heat treatment simulations and real-world tire testing up to 50,000 km.
Implementation Method 1
containing at least one copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound
Implementation Method 2
the heat treatment involves allowing the rubber composition to stand at a temperature of 90° C. and an oxygen concentration of 20% for 336 hours
Implementation Method 3
the copolymer is at least one hydrogenated styrene-butadiene rubber having a weight average molecular weight of 200,000 to 2,000,000 and a degree of hydrogenation of 60 mol % or more
Data Source
AI summary
The purpose is to provide rubber compositions and pneumatic tires which have reduced changes in complex modulus E* over time. The present invention relates to rubber compositions containing at least one copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound, the rubber compositions having a heat aging resistance index defined by equation (1) of 27 or less.