Styrenic Block Copolymer Composition for Balanced Viscosity and Strength
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Solution Overview
Problem
There is a need to produce styrenic block copolymers with a balance of low viscosity, high tensile strength, and isotropic mechanical properties, which existing technologies have not adequately addressed.
Innovation Solution
A block copolymer composition comprising specific weight percentages of tetra-branched, tri-branched, di-branched, and linear diblock copolymers, coupled using an alkoxy silane coupling agent, and subsequently hydrogenated to enhance mechanical properties and reduce viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional coupling methods are used to produce styrenic block copolymers, then polymer composition is achieved, but viscosity is high and mechanical properties are insufficient
Solution Approach 1:
The patent applies parameter changes by controlling the molecular weight of the conjugated diene block (Mn = 7,000 to 20,000 g/mol) and the styrene block (Mn = 4,000 to 7,500 g/mol) within specific ranges, and by controlling the ratio of branched to linear copolymers (60-95 wt% di-branched). These parameter optimizations resolve the contradiction by achieving high tensile strength through appropriate molecular weight selection while maintaining low viscosity through controlled branching architecture.
2Strength
If branched copolymers are increased to improve mechanical properties, then tensile strength improves, but viscosity increases
Solution Approach 1:
The patent applies local quality by creating a heterogeneous mixture of different branched architectures (di-branched, tri-branched, and tetra-branched copolymers) rather than using a single uniform structure. The di-branched copolymer (60-95 wt%) provides the primary mechanical strength, while tri-branched (0-36 wt%) and tetra-branched (0-5 wt%) components contribute to isotropic properties. This local differentiation of structural quality allows optimization of both strength and viscosity characteristics.
Solution Approach 2:
The patent applies composite materials by combining multiple copolymer species with different branching degrees in a single composition. The composite consists of di-branched copolymer (60-95 wt%), tri-branched copolymer (0-36 wt%), and tetra-branched copolymer (0-5 wt%), each contributing different properties. This composite approach resolves the contradiction by distributing the functional requirements across different components, achieving high tensile strength through the di-branched phase while the overall composition maintains low viscosity.
3Strength
If molecular weight is increased to improve tensile strength, then strength improves, but solution viscosity increases
Solution Approach 1:
The patent applies parameter changes by establishing specific molecular weight ranges: conjugated diene block Mn = 7,000 to 20,000 g/mol and styrene block Mn = 4,000 to 7,500 g/mol. These optimized parameters achieve the contradiction resolution by ensuring that the molecular weight is sufficient for high tensile strength (≥1,500 psi) while remaining low enough to maintain solution viscosity between 100-400 cP at 20 wt% concentration.
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 solution achieves a balance of low viscosity and high tensile strength with isotropic mechanical properties, as demonstrated by improved solution viscosity, melt flow rate, and tensile strength measurements.
Implementation Method 1
lithium-terminated polymers of one or more conjugated dienes and of one or more mono alkenyl arenes are coupled by reaction with an alkoxy silane coupling agent
Implementation Method 2
The polymer compositions are subsequently selectively hydrogenated
Data Source
AI summary
This disclosure relates to a block copolymer composition comprising a tetra-branched block copolymer (IV) having a true number average molecular weight of 40,000 to 120,000 represented by the general formula (A-B)4X; a tri-branched block copolymer (III) having a true number average molecular weight of from 30,000 to 90,000 represented by the general formula (A-B)3X; di-branched block copolymer (II) having a true number average molecular weight of from 20,000 to 60,000 represented by the general formula (A-B)2X; and a linear diblock copolymer (I) having a true number average molecular weight of from 10,000 to 30,000 represented by the general formula A-B; where A represents a polymer block of a mono alkenyl arene; B represents a polymer block of a conjugated diene, wherein the B has a true number average molecular weight ranging from 7,000 to 20,000 g/mol; and X represents the residue of an alkoxy silane coupling agent.