Rubber composition for tire tread and tire
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Solution Overview
Problem
Existing rubber compositions for tire treads face challenges in simultaneously achieving low-temperature performance and wet grip performance, as incorporating butadiene rubber for low-temperature performance tends to deteriorate wet grip, and adding resin for wet grip performance compromises low-temperature performance, while high silica content makes it difficult to maintain fracture strength.
Innovation Solution
A rubber composition comprising 100 parts by mass of a diene rubber component with a butadiene rubber and styrene butadiene rubber having a glass transition temperature of -50°C or less, 60 to 200 parts by mass of silica, and 20 to 60 parts by mass of a terpene-based resin with a β-pinene unit content of 40 mass%, along with a thioester group-containing silane coupling agent, which improves silica dispersion and fracture strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If butadiene rubber is incorporated to improve low-temperature performance, then low-temperature performance is improved, but wet grip performance deteriorates
Solution Approach 1:
The invention changes the glass transition temperature parameter of the diene rubber component to -60°C or lower through specific rubber selection and blending ratios. This parameter change allows the rubber to maintain softness at low temperatures while the terpene-based resin compensates for wet grip performance, resolving the contradiction between low-temperature and wet grip performance.
Solution Approach 2:
The invention uses a composite material system combining diene rubber component, silica, and terpene-based resin. The resin acts as a modifier that compensates for the wet grip deterioration caused by low-Tg rubber, creating a synergistic composite that achieves both low-temperature flexibility and wet grip performance simultaneously.
2Reliability
If resin is added to improve wet grip performance, then wet grip performance is improved, but low-temperature performance deteriorates
Solution Approach 1:
The invention carefully controls the glass transition temperature of the diene rubber component to be -60°C or lower, and selects specific terpene-based resin with β-pinene unit content of 40 mass% or more. By optimizing these parameters, the resin improves wet grip without excessively raising the overall Tg, thus maintaining low-temperature performance.
3Reliability
If large amount of silica is incorporated to improve wet grip performance, then wet grip performance is improved, but fracture strength becomes difficult to maintain
Solution Approach 1:
The invention uses a silane coupling agent as an intermediary substance between silica and rubber matrix. The coupling agent improves silica dispersion and interfacial adhesion, allowing high silica content (60-200 parts) to be incorporated while maintaining fracture strength through enhanced stress transfer at the filler-matrix interface.
4Temperature
If butadiene rubber is incorporated for low-temperature performance, then low-temperature performance is improved, but the glass transition temperature of the rubber composition decreases leading to wet grip deterioration
Solution Approach 1:
The invention creates a composite system where terpene-based resin (20-60 parts) modifies the rubber composition. The resin compensates for the wet grip deterioration caused by low Tg rubber by providing appropriate Tg and polar interactions with silica, achieving synergistic performance in both low-temperature flexibility and wet grip.
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
This composition effectively achieves simultaneous low-temperature performance, wet grip performance, and improved fracture strength, making it suitable for winter and all-season tires.
Implementation Method 1
a thioester group-containing silane coupling agent, which improves silica dispersion and fracture strength
Implementation Method 2
the glass transition temperature of the entire rubber composition decreases, leading to a tendency for wet grip performance to deteriorate
Data Source
AI summary
A rubber composition for a tire tread according to an embodiment includes 100 parts by mass of a diene rubber, 60 to 200 parts by mass of silica, and 20 to 60 parts by mass of a terpene-based resin having a β-pinene unit content of 40 mass% or more, and further includes 5 to 20 parts by mass of a thioester group-containing silane coupling agent per 100 parts by mass of silica. The diene rubber component contains a butadiene rubber and a styrene butadiene rubber having a glass transition temperature of -50°C or less, in which the content of the butadiene rubber is 20 parts by mass or more, and the average glass transition temperature of the diene rubber component is -60°C or less.