Thiocarboxyl Silane Rubber Process for Scorch Control
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Solution Overview
Problem
Current rubber compositions using silica/silane systems face challenges with high reactivity leading to scorch during processing, incomplete filler dispersion, and suboptimal reinforcing efficiency, resulting in increased production costs and unsatisfactory end-use properties like abrasion resistance.
Innovation Solution
A process involving thiocarboxyl-functional hydrolyzable silane, rubber with carbon-carbon double bonds, silane-reactive filler, activating agent, and water, subjected to reactive-mechanical-working conditions followed by vulcanizing agent addition and non-reactive-mechanical-working conditions, to achieve improved filler dispersion and coupling without premature crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polysulfurized alkoxysilanes are used as coupling agents, then coupling efficiency is improved, but processing quality deteriorates due to scorch from high reactivity
Solution Approach 1:
The silane is pre-grafted onto the filler surface during filler preparation before rubber compounding. This preliminary action ensures the silane is already attached to the filler, preventing premature reaction with rubber and eliminating scorch during mixing, while still achieving effective coupling in the final product
Solution Approach 2:
The process is segmented into distinct stages: (1) silane grafting onto filler under controlled conditions, (2) drying to remove water, and (3) subsequent rubber compounding. This segmentation allows each step to be optimized independently, preventing unwanted side reactions during mixing
2Ease of manufacture
If multiple non-productive mixing cycles are used, then scorch is reduced, but production time and cost increase
Solution Approach 1:
The silane grafting is performed as a preliminary action during filler preparation, so that when the filler is incorporated into rubber, the silane is already activated and ready to couple. This eliminates the need for multiple non-productive mixing cycles, allowing single-pass efficient production
Solution Approach 2:
The grafted silane acts as an intermediary that is pre-prepared on the filler surface. This intermediary form prevents direct reaction between free silane and rubber during mixing, enabling efficient single-stage processing without scorch
3Ease of manufacture
If blocked mercapto-functional silanes are used, then processing problems are reduced, but filler dispersion and coupling efficiency deteriorate
Solution Approach 1:
The invention changes the chemical parameters by using thiocarboxyl-functional silane instead of blocked mercapto-functional silane. The thiocarboxyl group provides both improved processing behavior and superior coupling efficiency, achieving the desired balance through parameter optimization
Solution Approach 2:
The invention creates a composite structure where silane is grafted onto the filler surface, forming a silane-modified filler. This composite material combines the benefits of good processing behavior with enhanced filler-rubber coupling, achieving properties superior to either component alone
4Ease of manufacture
If silane is partially removed during mixing, then processing is improved, but filler dispersion and coupling efficiency deteriorate
Solution Approach 1:
The silane is pre-attached to the filler surface in a controlled grafting step before mixing. This preliminary attachment ensures the silane remains on the filler during subsequent processing, maintaining both good processing behavior and effective filler dispersion without partial removal
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 process results in rubber articles with enhanced mechanical properties, including increased reinforcing efficiency, abrasion resistance, and higher modulus at 300% elongation, while minimizing scorch and processing waste.
Implementation Method 1
thiocarboxyl-functional hydrolyzable silane
Implementation Method 2
silane only partially reacting with the filler surface
Implementation Method 3
filler coupling to the rubber matrix
Implementation Method 4
adding at least one vulcanizing agent (vi) to the composition of step (b); mixing the composition of step (c) under non-reactive-mechanical-working conditions; and, optionally, curing the rubber composition
Implementation Method 5
in the substantial absence of vulcanizing agent(s)
Data Source
AI summary
A process for preparing a rubber composition comprises:(a) forming a mixture of:(i) at least one thiocarboxyl-functional hydrolyzable silane,(ii) at least one rubber containing carbon-carbon double bonds,(iii) at least one silane-reactive filler,(iv) at least one activating agent, and(v) water;(b) mixing the composition formed in step (a) under reactive-mechanical-working conditions and in the absence of vulcanizing agent(s);(c) adding at least one vulcanizing agent (vi) to the composition of step (b);(d) mixing the composition of step (c) under non-reactive-mechanical-working conditions; and,(e) optionally, curing the rubber composition of step (d).