Pneumatic Tire Bead Apex Rubber Composition for Run-Flat Durability
Solution Overview
Problem
Current rubber compositions for pneumatic tire bead apexes and sidewall reinforcing layers face challenges in achieving balanced improvements in high-hardness properties, elongation at break, and self-heating properties while maintaining good processability, which is crucial for run-flat durability and fuel efficiency.
Innovation Solution
A rubber composition comprising 10-75% modified butadiene rubber, 5-40% polybutadiene rubber with 1,2-syndiotactic polybutadiene crystals, and 10-40% diene rubber, along with 35-65 parts by mass of carbon black with a BET specific surface area of 18-50 m^2/g, optimized with specific modifications and additives for improved properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large amount of carbon black with large reinforcing effect is used to increase complex elastic modulus (E*), then handling stability is improved, but fuel efficiency deteriorates
Solution Approach 1:
The patent changes the particle size parameter of carbon black from conventional small particles to large particles (D50: 20-50 μm, D90: 50-80 μm). This parameter change reduces the reinforcing effect per unit mass, allowing lower carbon black content (35-65 parts by mass) to achieve the required E*, thereby improving fuel efficiency while maintaining handling stability.
Solution Approach 2:
The patent creates a composite rubber composition combining multiple rubber components (modified butadiene rubber, polybutadiene rubber with 1,2-syndiotactic polybutadiene crystals, and other diene rubber) with large particle size carbon black. This composite structure achieves synergistic effects where the specific rubber composition enhances the reinforcing efficiency of the large particle carbon black, maintaining E* while reducing carbon black content for better fuel efficiency.
2Loss of energy
If the amount of carbon black is reduced to improve fuel efficiency, then fuel efficiency is improved, but complex elastic modulus (E*) decreases
Solution Approach 1:
The patent changes the particle size parameter of carbon black to large particles (D50: 20-50 μm, D90: 50-80 μm) and optimizes the quantity to 35-65 parts by mass. This parameter optimization allows achieving sufficient E* with reduced carbon black content, improving fuel efficiency while maintaining handling stability.
Solution Approach 2:
The patent applies large particle size carbon black specifically in the bead apex and sidewall reinforcing layer where structural support is critical. This localized application ensures adequate E* in key areas while reducing overall carbon black content for improved fuel efficiency.
3Loss of energy
If silica is used to improve fuel efficiency, then fuel efficiency is improved, but extrusion and building processabilities decrease
Solution Approach 1:
The patent extracts silica from the rubber composition and replaces it with large particle size carbon black. This extraction eliminates the processing problems associated with silica (poor extrusion and building processability) while maintaining fuel efficiency benefits through reduced overall filler content and use of large particle carbon black.
Solution Approach 2:
The patent uses conventional carbon black as a substitute for silica, leveraging its well-established processing characteristics. While carbon black has lower inherent fuel efficiency benefits compared to silica, the large particle size and optimized dosage (35-65 parts by mass) achieve comparable fuel efficiency without compromising processability.
4Loss of energy
If crosslinking agents such as sulfur or accelerators are added to provide high hardness and fuel efficiency, then fuel efficiency is improved, but elongation at break and tensile strength decrease
Solution Approach 1:
The patent optimizes the dosage of crosslinking agents (sulfur and accelerators) to balanced levels that achieve sufficient hardness and fuel efficiency without excessive crosslinking. This parameter optimization prevents over-crosslinking that would cause brittleness, maintaining adequate elongation at break and tensile strength while improving fuel efficiency.
5Loss of energy
If low-grade carbon black such as FEF and GPF is used, then fuel efficiency is improved, but elongation at break decreases and run-flat durability is reduced
Solution Approach 1:
The patent changes the particle size parameter to large particles (D50: 20-50 μm, D90: 50-80 μm) and optimizes the dosage to 35-65 parts by mass. This parameter optimization provides sufficient reinforcing effect to maintain elongation at break and run-flat durability while achieving fuel efficiency benefits through reduced overall filler content.
Solution Approach 2:
The patent creates a composite system combining specific rubber components (modified butadiene rubber, polybutadiene rubber with 1,2-syndiotactic polybutadiene crystals) with large particle size carbon black. This composite structure achieves synergistic reinforcement that maintains mechanical properties and run-flat durability while improving fuel efficiency.
Data Source
AI summary
Provided is a pneumatic tire including a bead apex and/or sidewall reinforcing layer, which achieves balanced improvements in high-hardness properties, elongation at break, and self-heating properties to provide good run-flat durability while maintaining good processability. The pneumatic tire includes a bead apex and/or sidewall reinforcing layer formed from a rubber composition, the composition containing a rubber component (A) and carbon black (B), the rubber component (A) containing, per 100% by mass thereof: 10-75% by mass of a modified butadiene rubber (A1) with a cis content of 50% by mass or less; 5-40% by mass of a polybutadiene rubber (A2) containing 1,2-syndiotactic polybutadiene crystals; and 10-40% by mass of a diene rubber (A3) different from (A1) and (A2), the composition containing 35-65 parts by mass of carbon black (B) per 100 parts by mass of rubber component (A), the carbon black (B) having a BET specific surface area of 18-50 m2/g.