Rubber-Cord Composite Adhesion After Heat and Humidity Aging

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Solution Overview

Problem

Conventional rubber/cord composites face challenges in maintaining good adhesion both initially and after high temperature and high humidity aging, which affects the performance and durability of pneumatic tires.

Innovation Solution

A composite with a topping rubber composition having a fatty acid content of 0.8% by mass or less and a copper-containing layer on the adherend, along with a sulfate ion concentration of 0.8% by mass or less in the rubber composition, ensures strong adhesion between the rubber and the cord, even under harsh conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional rubber compositions with higher fatty acid content are used to improve initial adhesion to cords, then initial adhesion is enhanced, but adhesion deteriorates after high temperature and high humidity aging

Engineering Contradiction:
Improveinitial adhesionVSAvoidadhesion after aging
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The invention changes the chemical composition parameters of the rubber composition by strictly limiting fatty acid content to 0.8% by mass or less. This parameter change resolves the contradiction by eliminating the source of adhesion deterioration (fatty acids that migrate and cause degradation) while maintaining sufficient initial adhesion through alternative bonding mechanisms between the rubber and copper-containing layer.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If rubber compositions containing more adhesion promoters are used to ensure good adhesion after aging, then adhesion after aging is improved, but initial adhesion performance is compromised

Engineering Contradiction:
Improveadhesion after agingVSAvoidinitial adhesion
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The invention extracts and removes the problematic component (fatty acids) from the rubber composition by imposing a strict content limit of 0.8% by mass or less. This extraction approach resolves the contradiction by eliminating the substance that causes adhesion deterioration over time, allowing the system to achieve both good initial adhesion and sustained adhesion after aging without relying on excessive adhesion promoters.

Inventive Principle:
Principle #2Taking out (Extraction)

3Ease of manufacture

If natural rubber with higher fatty acid content is used to simplify material selection, then ease of manufacture is improved, but adhesion performance after aging deteriorates

Engineering Contradiction:
Improvematerial selectionVSAvoidadhesion after aging
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The invention changes the selection criterion for natural rubber from accepting typical commercial grades to specifically selecting rubber with fatty acid content of 0.8% by mass or less. This refined parameter specification resolves the contradiction by guiding material selection toward rubber that maintains adhesion performance after aging, while still being manufacturable through standard processes.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP3421528B1Composite and pneumatic tire
Publication Date: 2023.11.22 SUMITOMO RUBBER INDUSTRIES LTD

AI summary

The present invention provides a composite that has good initial adhesion and good adhesion after high temperature and high humidity aging. Provided is a composite including: a topping rubber composition having a fatty acid content of 0.8% by mass or less; and an adherend plated with a copper-containing layer.