Unsaturated Siloxane Coupling for Lower-Viscosity Polydiene Rubber
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Solution Overview
Problem
There is a need for alternative coupling agents for coupling diene rubbers, as existing coupling agents may not provide optimal processing and performance characteristics.
Innovation Solution
A method of making polydiene rubber involving polymerizing aliphatic conjugated diene monomers to produce polymers with reactive chain ends, and then reacting these ends with a coupling agent comprising 2 to 20 unsaturated siloxane units, which forms a cyclic structure but is not polycyclic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional coupling agents (silicon tetrachloride, methyltrichlorosilane, etc.) are used to improve diene rubber processing, then the polymer chains are linked to create branched or star-shaped architecture which reduces Mooney viscosity and facilitates processing, but there is a need for alternative coupling agents to provide optimal processing and performance characteristics
Solution Approach 1:
The patent changes the chemical parameters of the coupling agent by using unsaturated siloxane units (containing C=C bonds) instead of conventional saturated silanes. This parameter change provides both the coupling function to link polymer chains and introduces unsaturation that enables additional reactions during vulcanization, thus resolving the need for alternatives while maintaining processing benefits
Solution Approach 2:
The coupling agent combines siloxane units with unsaturated hydrocarbon groups (vinyl, allyl, or propenyl groups) to create a composite molecular structure. This composite structure integrates the chain-linking capability of siloxanes with the reactivity of unsaturated groups, achieving both improved processing and enhanced vulcanization performance
2Manufacturing precision
If coupling agents are used to link polymer chains and create branched or star-shaped architecture, then the molecular weight distribution broadens and Mooney viscosity reduces, but the specific structure (cyclic with 2-20 unsaturated siloxane units, not polycyclic) is required to achieve optimal results
Solution Approach 1:
The patent specifies local structural qualities of the coupling agent: cyclic structure with 2-20 unsaturated siloxane units per molecule, with each unit containing specific functional groups. This local quality control ensures the coupling agent creates the desired branched architecture without forming polycyclic structures, achieving precise molecular weight distribution control
Solution Approach 2:
The coupling agent is segmented into multiple unsaturated siloxane units (2-20 per molecule) rather than using a single unit or polycyclic structure. This segmentation allows controlled branching without excessive complexity, optimizing the balance between molecular weight distribution broadening and processability
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 use of unsaturated siloxane-based coupling agents allows for the creation of polydiene rubbers with improved molecular weight distribution and reduced Mooney viscosity, facilitating better processing and potentially enhancing the performance of rubber compounds.
Implementation Method 1
Coupling agents link the polymer chains of the rubbers with each other to create a branched or star-shaped polymer architecture
Implementation Method 2
polymerizing at least one aliphatic conjugated diene monomer to produce a polymer having reactive polymer chain ends
Data Source
AI summary
Method of making a polydiene rubber comprising(i) polymerizing at least one aliphatic conjugated diene monomer, preferably having from 4 to 25 carbon atoms, to produce polymers having reactive polymer chain ends,(ii) reacting at least some of the reactive polymer chain ends with a coupling agent comprising from 2 to 20 unsaturated siloxane units, preferably from 3 to 15 units, more preferably from 3 to 10 units.Also provided are polydiene rubbers obtained by the method, curable compositions comprising the polydiene rubber and composition comprising the cured polydiene rubber.