Styrene-Isoprene Copolymer Durability

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Solution Overview

Problem

Synthetic polyisoprene used in rubber compositions lacks durability compared to natural rubber, particularly in terms of fracture resistance, abrasion resistance, and crack-growth resistance, and existing methods to improve these properties are inadequate.

Innovation Solution

A styrene-isoprene copolymer with a styrene block at its terminals, where styrene monomers constitute less than 5 mol% and cis-1,4 bond content from isoprene is at least 95%, is developed to enhance the durability of rubber compositions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If synthetic polyisoprene is used as an alternative to natural rubber, then it can be produced synthetically, but it has poor durability compared to natural rubber

Engineering Contradiction:

ImprovedurabilityVSAvoidsynthetic production

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the microstructural parameters of synthetic polyisoprene by increasing the cis-1,4 bond content to at least 95% and controlling styrene content below 5 mol%, which transforms the material properties to achieve durability comparable to natural rubber while maintaining synthetic production advantages

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite copolymer structure combining polyisoprene with a styrene block at the terminal, where the styrene block serves as a functional component that enhances durability without significantly affecting the overall polyisoprene properties, achieving natural rubber-like performance

Inventive Principle:

Principle #40Composite materials

2Reliability

If cis-1,4 bond content is increased to improve elongation crystallinity, then durability is improved, but manufacturing complexity increases

Engineering Contradiction:

ImprovedurabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs a two-stage polymerization process where styrene is first polymerized to form a block, then isoprene is added to form the copolymer with high cis-1,4 content. This preliminary formation of the styrene block simplifies the overall process by pre-organizing the structure before final copolymerization

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses an organometallic catalyst as an intermediary to achieve high cis-1,4 bond content in the isoprene portion. The catalyst mediates the polymerization reaction to selectively form the desired microstructure, simplifying the manufacturing process compared to conventional methods

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If styrene content is kept low to maintain polyisoprene properties, then natural rubber-like properties are preserved, but copolymerization control becomes more difficult

Engineering Contradiction:

Improvenatural rubber propertiesVSAvoidcopolymerization control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent segments the copolymer structure by concentrating styrene into a terminal block rather than distributing it randomly throughout the chain. This segmentation allows low overall styrene content (<5 mol%) while maintaining polyisoprene properties, as the styrene is localized to specific regions rather than dispersed throughout the material

Inventive Principle:

Principle #1Segmentation

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 styrene-isoprene copolymer achieves rubber compositions with properties similar to natural rubber, including improved fracture resistance, abrasion resistance, and crack-growth resistance, thereby enhancing the durability of tires and other rubber products.

Implementation Method 1

synthesizing a polymer or an oligomer by polymerization of a styrene monomer in the presence of a catalyst

Methodology Applied

Scientific EffectPolymerization:

Implementation Method 2

adding an isoprene monomer to the polymer or the oligomer for polymerization

Methodology Applied

Scientific EffectPolymerization:

Implementation Method 3

cis-1,4 bond content of a portion derived from isoprene accounts for at least 95% in total

Methodology Applied

Scientific EffectCis-1,4 bonding:

Data Source

PatentEP2873681B1Isoprene copolymer and method of producing the same

Publication Date: 2018.04.18 BRIDGESTONE CORP

AI summary

A copolymer having properties (durability (fracture resistance, abrasion resistance, and crack-growth resistance)) similar to those of natural rubber and a method of producing the copolymer are provided. An isoprene copolymer has a styrene block or a butadiene block at a terminal thereof, wherein styrene monomers account for less than 5 mol% of all monomers forming the isoprene copolymer having the styrene block; butadiene monomers account for 10 mol% or less of all monomers forming the isoprene copolymer having the butadiene block; and cis-1,4 bond content of a portion derived from isoprene accounts for at least 95% in total.