Sidewall Rubber Composition Conductivity Cost Balance

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Solution Overview

Problem

Existing rubber compositions for tire sidewalls face challenges in achieving a balance between conductivity, anti-spew-cutting property, and extrusion processability while maintaining low production costs, with high-cost carbon blacks and complex production processes being major issues.

Innovation Solution

A rubber composition comprising 2 to 15 parts by mass of wet processed silica with a BET specific surface area of 70 to 250 m^2/g and 40 to 62 parts by mass of carbon black with a BET specific surface area of 37 to 125 m^2/g, along with phenylenediamine antioxidant and/or quinone antioxidant, and 2,2,4-trimethyl-1,2-dihydroquinoline polymer, without a silane coupling agent, to achieve the desired properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high structure carbon black is used to secure conductivity, then conductivity is improved, but production cost increases

Engineering Contradiction:

ImproveconductivityVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive high structure carbon black with cheaper conventional carbon black (N220, N330, or N550) to reduce production cost while maintaining adequate conductivity through optimized formulation and processing

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the carbon black parameters by selecting specific types (N220, N330, or N550) and controlling their content (20-40 parts by mass per 100 parts rubber component) along with silica content (10-30 parts by mass) to achieve the desired balance between conductivity and cost

Inventive Principle:

Principle #35Parameter changes

2Reliability

If ply topping rubber layer is thickened to improve conductivity, then conductivity is improved, but heat build-up property and rolling resistance deteriorate

Engineering Contradiction:

ImproveconductivityVSAvoidheat build-up property and rolling resistance

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the approach from increasing layer thickness to optimizing filler composition and distribution within the existing sidewall structure, using specific ratios of carbon black and silica to achieve conductivity without adding excess material that would increase heat build-up

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical approach of thickening the rubber layer with a compositional approach, using electrically conductive filler particles (carbon black and silica) dispersed within the rubber matrix to achieve conductivity while maintaining optimal layer thickness for heat dissipation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If content of natural rubber is increased to prevent spew cutting, then anti-spew-cutting property is improved, but production cost increases

Engineering Contradiction:

Improveanti-spew-cutting propertyVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the approach from increasing natural rubber content to optimizing the filler system (carbon black and silica) and their interaction with the rubber matrix, improving spew cutting resistance through enhanced filler-rubber bonding and optimized compounding rather than simply adding more expensive natural rubber

Inventive Principle:

Principle #35Parameter changes

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 composition provides excellent conductivity, anti-spew-cutting property, and extrusion processability in a balanced manner, reducing production costs and improving tire performance without the need for a silane coupling agent.

Implementation Method 1

The conductivity of a tire is a property for discharging static electricity accumulated on a vehicle to a ground, and generally static electricity is discharged through a rim, a clinch, a ply, a sidewall, a belt or a breaker

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

Without such discharging, static electricity is accumulated on a vehicle and there arises a problem such that a person riding on a vehicle receives an electric shock, a spark occurs when filling fuel to cause a fire

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Data Source

PatentEP2743303B1Sidewall rubber composition and tire using same

Publication Date: 2020.03.18 SUMITOMO RUBBER INDUSTRIES LTD

Figure 1

AI summary

An object of the present invention is to provide a rubber composition for a sidewall having excellent conductivity, anti-spew cutting property and extrusion processability in good balance and assuring low production cost. The present invention provides a rubber composition for a sidewall comprising 2 to 15 parts by mass of a wet processed silica having a BET specific surface area of 70 to 250 m2/g and 40 to 62 parts by mass of a carbon black having a BET specific surface area of 37 to 125 m2/g based on 100 parts by mass of a diene rubber component, wherein the rubber composition does not contain a silane coupling agent, and has a volume resistivity of not more than 1×108 Ω·cm