Dual Functionalized SBR Rubber Composition for Silica Dispersion
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Solution Overview
Problem
High loadings of pre-hydrophobated precipitated silica in rubber compositions can lead to accelerated sulfur cure rates, resulting in pre-curing or scorching, and may reduce the beneficial effects on rolling resistance and fuel economy when combined with zinc fatty acid salts, necessitating a balance to maintain optimal properties.
Innovation Solution
Incorporating a pre-formed zinc salt of fatty acids with pre-hydrophobated precipitated silica and using dual functionalized styrene/butadiene elastomers with reactive groups to manage cure rates and maintain improved rolling resistance and fuel economy, while minimizing zinc oxide addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high loadings of pre-hydrophobated precipitated silica are added to rubber composition, then rolling resistance is reduced and fuel economy is improved, but sulfur cure rate increases causing pre-curing or scorching
Solution Approach 1:
A zinc salt of a fatty acid is introduced as an intermediary substance between the pre-hydrophobated precipitated silica and the rubber matrix. This intermediary acts as a cure rate modulator that counterbalances the accelerated sulfur cure rate induced by high silica loadings, preventing pre-curing or scorching while preserving the low rolling resistance benefits of the silica reinforcement
Solution Approach 2:
The invention changes the chemical parameter of the zinc salt of fatty acid from being formed in situ (traditional approach) to being pre-formed and added directly (innovative approach). This parameter change allows precise control over the cure rate modulation, enabling the system to maintain both high silica loading for low rolling resistance and controlled cure characteristics to prevent scorching
2Ease of manufacture
If pre-formed zinc salt of fatty acid is added with pre-hydrophobated silica, then cure rate is balanced and processability is improved, but rebound property increases and tangent delta decreases reducing rolling resistance benefit
Solution Approach 1:
The invention optimizes the parameter of zinc salt loading level to achieve a balance point. By controlling the amount of pre-formed zinc salt of fatty acid added, the system achieves sufficient cure rate moderation for good processability while limiting the increase in rebound property and tangent delta changes that would adversely affect rolling resistance
Solution Approach 2:
The invention applies partial action by using a controlled, moderate amount of zinc salt rather than excessive amounts. This partial application is sufficient to counterbalance the silica-induced cure acceleration and provide good processability, while avoiding over-modulation that would excessively increase rebound property and harm rolling resistance performance
3Ease of operation
If zinc oxide and fatty acids are added to form zinc salt in situ, then traditional compounding is maintained, but cure rate acceleration by silica is not sufficiently counterbalanced
Solution Approach 1:
The invention applies preliminary action by pre-forming the zinc salt of fatty acid before adding it to the rubber composition. This preliminary preparation ensures that the zinc salt is immediately available to counterbalance the silica-induced cure acceleration from the start of mixing, providing more effective cure rate control compared to in situ formation which occurs gradually during processing
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 combination of pre-formed zinc fatty acid salts and dual functionalized styrene/butadiene elastomers with pre-hydrophobated silica effectively balances cure rates, maintaining low rolling resistance and improved fuel economy while ensuring good processability and traction properties.
Implementation Method 1
the addition of a preferably pre-formed zinc salt of fatty acid(s) with the silica, preferably the pre-hydrophobated precipitated silica, to the rubber composition
Implementation Method 2
dual functionalized styrene/butadiene elastomers with reactive groups to manage cure rates
Implementation Method 3
the silica reinforcement may be provided as a pre-hydrophobated precipitated silica which has been hydrophobated by reaction with the silica coupling agent prior to its addition to the rubber composition
Data Source
AI summary
A rubber composition is disclosed. comprising, based on parts by weight per 100 parts by weight rubber (phr): (A) 100 phr of at least one conjugated diene-based elastomer which includes: (1) 20 to 100 phr of a functionalized styrene/butadiene elastomer derived from organic solvent solution polymerization of styrene and 1,3-butadiene monomers which contains 10 to 50 percent bound styrene and has a vinyl 1,2-content based on its butadiene component in a range of from 10 to 70 percent, said functionalized styrene/butadiene elastomer comprising: (a) 10 to 50 phr of a first functionalized styrene/butadiene elastomer containing functional groups comprising siloxy and amine groups reactive with hydroxyl groups on a silica, and (b) 10 to 50 phr of a second functionalized styrene/butadiene elastomer containing functional groups comprising siloxy and thiol groups reactive with hydroxyl groups on a silica; (B) 10 to 170 phr of a particulate rubber reinforcing filler; and (C) 0.1 to 10 phr of a zinc salt of a fatty acid soap. Also a pneumatic tire comprising such a rubber composition in its tread is disclosed.