Tread Cap Rubber Composition for Tire Chipping Resistance
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Solution Overview
Problem
The chipping resistance performance of conventional tires is insufficient, particularly when driving on uneven ground, necessitating further improvement.
Innovation Solution
A tire design with a cap rubber layer containing 40 to 60 parts by mass of styrene-butadiene rubber (SBR) with 20% or less styrene content, 30 parts by mass or less isoprene-based rubber, and up to 100 parts by mass of silica, along with a loss tangent of 0.25 or less, and a thickness ratio of the cap rubber layer to the base rubber layer of 2.3 or more, to enhance chipping resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional rubber compositions and tread surface shapes are used to improve chipping resistance, then some chipping resistance is achieved, but the chipping resistance performance is still not sufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the styrene content in SBR (20% or less) and the thickness ratio of cap rubber layer to base rubber layer (2.3 or more). These specific parameter ranges optimize the balance between chipping resistance and crack propagation suppression, resolving the insufficiency of conventional formulations.
Solution Approach 2:
The patent uses composite materials by combining SBR with low styrene content (20% or less) and isoprene-based rubber in specific proportions (40-60 parts SBR, 30 parts or less isoprene-based rubber per 100 parts rubber component). This composite approach creates synergistic effects that simultaneously improve chipping resistance and reduce crack propagation.
2Strength
If the cap rubber layer thickness is increased to improve chipping resistance, then chipping resistance improves, but heat build-up increases
Solution Approach 1:
The patent controls the thickness ratio parameter (cap rubber layer to base rubber layer) at 2.3 or more, which provides sufficient chipping resistance while the specific rubber composition (low styrene SBR with loss tangent ≤0.25) manages heat generation, balancing both requirements.
Solution Approach 2:
The patent applies local quality by creating a cap rubber layer with specific composition characteristics (low styrene content SBR, loss tangent ≤0.25) that is optimized for chipping resistance, while the base rubber layer has different composition suitable for heat management and overall structural integrity.
3Strength
If silica content is increased to improve reinforcing properties, then reinforcing properties improve, but manufacturing complexity increases
Solution Approach 1:
The patent specifies silica content within the range of 100 parts by mass or less per 100 parts rubber component, which provides adequate reinforcing properties while avoiding excessive manufacturing complexity. This parameter optimization balances performance and manufacturability.
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 tire design effectively suppresses the propagation of impacts and cracks, improving chipping resistance while maintaining reinforcing properties and reducing heat build-up, thereby enhancing durability and ride comfort.
Implementation Method 1
a loss tangent 30°C tan δ of 0.25 or less measured under conditions of temperature of 30°C, frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%, and deformation mode: tensile
Data Source
AI summary
A tire having improved chipping resistance performance is provided, wherein the tire has a tread portion, the tread portion has a cap rubber layer and a base rubber layer provided radially inward of the cap rubber layer, the cap rubber layer contains, as a rubber component, 40 parts by mass or more and 60 parts by mass or less of styrene-butadiene rubber (SBR) with a styrene content of 25% by mass or less, and 30 parts by mass or less of isoprene-based rubber, in 100 parts by mass of the rubber component, and, as a filler, 100 parts by mass or less of silica with respect to 100 parts by mass of the rubber component; and is formed from a rubber composition having a loss tangent 30°C tan δ of 0.25 or less measured under conditions of temperature of 30°C, frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%, and deformation mode: tensile; and the ratio of the thickness of the cap rubber layer to the thickness of the base rubber layer is 2.3 or more.