Rubber Composition for Pneumatic Tires Using Molecular Weight Control
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Solution Overview
Problem
Current rubber compositions for high-performance tires face challenges in achieving a balance between grip performance, durability of grip performance, abrasion resistance, processability, and bleed resistance, with existing solutions often resulting in trade-offs between these properties.
Innovation Solution
A rubber composition is developed with a high molecular weight diene polymer and a low molecular weight diene polymer, specifically formulated to have a temperature dependence curve of tan δ with a half-width of 45 or less, a temperature dependence of hardness of 4.3 or less, and a peak temperature of 10° C. or lower, utilizing a combination of high molecular weight styrene-butadiene rubber and liquid styrene-butadiene rubber with controlled styrene content and solubility parameters to enhance grip, durability, and abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SBR with high glass transition temperature is used to improve grip performance, then grip performance is improved, but temperature dependence increases and processability deteriorates
Solution Approach 1:
The patent changes the molecular weight parameter of SBR from conventional high molecular weight to low molecular weight (number average molecular weight Mn: 10,000-50,000, weight average molecular weight Mw: 30,000-100,000). This parameter change reduces the glass transition temperature and temperature dependence, thereby improving processability while maintaining grip performance through optimized molecular weight distribution and combination with other rubber components.
Solution Approach 2:
The patent creates a composite rubber composition by combining low molecular weight SBR with other rubber components (natural rubber, polybutadiene rubber, styrene-isoprene-butadiene rubber) and specific fillers. This composite approach balances the properties of individual components to achieve good grip performance, processability, and temperature dependence characteristics simultaneously.
2Reliability
If process oil is replaced with high softening point resin to improve grip performance, then grip performance is improved, but temperature dependence increases
Solution Approach 1:
The patent changes the softener component from high softening point resin to specific process oils with optimized softening points (50-150°C). This parameter change in the softener's physical properties reduces temperature dependence while maintaining grip performance through proper selection of process oil type and amount (5-30 parts by mass per 100 parts by mass of rubber component).
3Reliability
If small particle size carbon black is used to improve grip performance, then grip performance is improved, but carbon black dispersion becomes poor and abrasion resistance reduces
Solution Approach 1:
The patent applies local quality by using different particle size carbon blacks in specific proportions and positions within the rubber composition. It combines small particle size carbon black (for grip performance at the rubber-surface interface) with large particle size carbon black (for structural strength and abrasion resistance in the bulk). The specific surface area ratio and amount of each carbon black type are precisely controlled to optimize both grip performance and abrasion resistance.
4Ease of manufacture
If low molecular weight diene polymer is used to improve processability, then processability is improved, but bleed resistance deteriorates
Solution Approach 1:
The patent optimizes the molecular weight parameters of the diene polymer by specifying narrow ranges for number average molecular weight (10,000-50,000) and weight average molecular weight (30,000-100,000), with molecular weight ratio Mw/Mn controlled at 1.05-2.00. This precise parameter control ensures low molecular weight for processability while preventing excessive low molecular weight components that would cause bleeding.
Solution Approach 2:
The patent uses local quality by combining low molecular weight diene polymer (for processability) with high molecular weight diene polymer (for bleed resistance). The composition includes both low molecular weight components (10-50 parts by mass per 100 parts by mass of rubber component) and high molecular weight components (50-90 parts by mass per 100 parts by mass of rubber component), creating a balanced molecular weight distribution that provides both processability and compositional stability.
Data Source
AI summary
The present invention provides a rubber composition excellent in grip performance, durability of grip performance, and abrasion resistance. Also provided is a pneumatic tire formed from the rubber composition. The present invention relates to a rubber composition exhibiting a temperature dependence curve of tan δ with a half-width defined by Equation (1) of 45 or less as measured at a strain of 0.1% and a frequency of 10 Hz, the rubber composition having a temperature dependence of hardness defined by Equation (2) of 4.3 or less, the temperature dependence curve having a peak temperature of 10° C. or lower,half-width=(temperature at half-peak height on high temperature side)−(temperature at half-peak height on low temperature side), Equation (1):temperature dependence of hardness=(hardness index at 0° C.)/(hardness index at 100° C.). Equation (2):