Cap Tread Rubber Composition for Low-Resistance Off-Road Tires
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Solution Overview
Problem
Existing pneumatic tires struggle to provide reduced rolling resistance while maintaining excellent off-road durability, wet performance, and snow performance in a compatible manner due to conflicting properties of tread rubber compositions.
Innovation Solution
A pneumatic tire design with a tread portion composed of two layers, a cap tread layer and an undertread layer, using a rubber composition of 50-100 parts silica, 5-25 parts carbon black, and specific styrene-butadiene rubber, along with a unique tread pattern, to enhance durability, wet, and snow performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tan δ at 0°C is increased to improve wet performance, then wet performance is improved, but tan δ at 60°C increases and rolling resistance cannot be reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the glass transition temperature (Tg) within -40°C to -10°C and tan δ at 0°C within 0.08 to 0.18, while maintaining tan δ at 60°C at 0.65 or less. This multi-parameter optimization resolves the contradiction by finding a specific range where both wet performance and rolling resistance are optimized simultaneously.
2Reliability
If butadiene rubber is increased to improve snow performance, then snow performance is improved, but dispersibility of silica degrades and rolling resistance reduction becomes difficult
Solution Approach 1:
The patent resolves this contradiction by changing the parameter composition of the rubber blend, specifying that styrene-butadiene rubber content is 20-40 mass% and butadiene rubber content is 5-20 mass%. This controlled composition maintains silica dispersibility while achieving excellent snow performance through optimized cold-temperature flexibility.
Solution Approach 2:
The patent uses composite materials by combining multiple rubber types (natural rubber, styrene-butadiene rubber, butadiene rubber, and isoprene rubber) in specific proportions, along with silica and carbon black fillers. This composite approach allows simultaneous achievement of snow performance, rolling resistance reduction, and silica dispersibility.
3Loss of energy
If silica dispersibility is improved to reduce rolling resistance, then rolling resistance is reduced, but off-road durability performance may degrade
Solution Approach 1:
The patent applies composite materials by combining silica (50-100 parts by mass) and carbon black (5-25 parts by mass) as filler components in the rubber composition. This dual-filler composite system maintains silica dispersibility for rolling resistance reduction while carbon black provides reinforcement for off-road durability.
Solution Approach 2:
The patent resolves this contradiction by optimizing the silica content within 50-100 parts by mass per 100 parts by mass of diene rubber, and controlling the carbon black content at 5-25 parts by mass. This parameter optimization ensures both good silica dispersibility and sufficient mechanical strength for off-road durability.
Data Source
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AI summary
Provided is a pneumatic tire that can provide reduced rolling resistance and improved off-road durability performance, wet performance, and snow performance and provide these performances in a compatible manner to a high degree. The cap tread layer (11) is made of a rubber composition in which 50 parts by mass to 100 parts by mass of silica and 5 parts by mass to 25 parts by mass of carbon black are blended per 100 parts by mass of diene rubber containing 50 mass% or more of natural rubber and 20 mass% or more and 40 mass% or less of styrene-butadiene rubber. As the styrene-butadiene rubber, terminal-modified styrene-butadiene rubber having a vinyl content of 35 mass% to 70 mass% is used. As the carbon black, carbon black having a nitrogen adsorption specific surface area N2SA of less than 130 m2/g is used. The rubber composition constituting the cap tread layer (11) is set to have a tensile product TB × EB of 12000 or more and a hardness of 60 or more and 70 or less.