Rubber Composition Zinc Oxide Aggregate Control Fatigue Resistance
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Solution Overview
Problem
Conventional rubber compositions using diene rubber and zinc oxide as a vulcanization accelerator face challenges in achieving excellent fatigue resistance due to the aggregation of zinc oxide, which leads to deterioration in reinforcement performance and wear resistance.
Innovation Solution
A rubber composition with a total volume fraction of zinc oxide aggregates greater than 20 μm of 0.008 or less, combined with a carbon black having a surface average acidic functional group amount of 0.15 to 3.00 μeq/m², and crosslinked with a density of 4.5×10⁻⁴ mol/cm³ or less, to enhance dispersibility and reduce aggregate size, thereby improving fatigue resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If zinc oxide is compounded in the rubber composition, then vulcanization acceleration is improved, but aggregate formation occurs leading to deterioration of reinforcement performance and wear resistance
Solution Approach 1:
The patent applies preliminary action by pre-dispersing zinc oxide in a masterbatch containing rubber, carbon black, and other additives before final compounding. This preliminary dispersion prevents aggregate formation during subsequent mixing processes, allowing the zinc oxide to maintain its vulcanization acceleration function without forming harmful aggregates that would deteriorate reinforcement performance
Solution Approach 2:
The patent uses a masterbatch as an intermediary medium to disperse zinc oxide. The masterbatch contains rubber, carbon black, and other additives that act as mediators to prevent zinc oxide aggregation. This intermediary approach allows effective dispersion of zinc oxide while maintaining its vulcanization acceleration capability
2Strength
If zinc oxide is dispersed at nanolevel to improve reinforcement performance, then breaking strength and wear resistance are improved, but fatigue resistance is not improved
Solution Approach 1:
The patent applies parameter changes by controlling the volume fraction of zinc oxide aggregates with diameter of 20 μm or more to be 0.008 or less. This precise parameter control ensures that zinc oxide is sufficiently dispersed to improve breaking strength and wear resistance, while simultaneously preventing the formation of large aggregates that would act as stress concentration points and reduce fatigue resistance
3Reliability
If zinc oxide aggregates with diameter of 20 μm or more are reduced to 0.008 or less by volume fraction, then fatigue resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by preparing a masterbatch with pre-dispersed zinc oxide before final compounding. This preliminary dispersion action achieves the required low aggregate volume fraction (0.008 or less) through controlled mixing in the masterbatch stage, rather than requiring complex dispersion processes during final product manufacturing
Solution Approach 2:
The patent applies segmentation by dividing the compounding process into two stages: masterbatch preparation and final compounding. This segmentation allows the complex dispersion requirement (achieving 0.008 or less aggregate volume fraction) to be addressed in the masterbatch stage, simplifying the final manufacturing process
Data Source
AI summary
As a rubber composition excellent in fatigue resistance and a method for producing the same, this disclosure provides a rubber composition containing a zinc oxide, wherein: a total volume of aggregates of the zinc oxide with a diameter of 20 μm or more is 0.008 or less in the rubber composition by volume fraction; and a method for producing the rubber composition, comprising: preparing a wet masterbatch by using a carbon black with a surface average acidic functional group amount (μeq/m2) of 0.15 or more and less than 3.00, preferably 0.40 or more and less than 1.50; and compounding a zinc oxide with the wet masterbatch.