Bio-based Thermally Expandable Microspheres via Copolymer Composition

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Solution Overview

Problem

Conventional thermally expandable microspheres are produced from petrochemical-based monomers, which are not sustainable, and replacing them with bio-based monomers is challenging due to compatibility and performance requirements such as surface energy, gas barrier properties, and viscoelastic properties needed for effective expansion.

Innovation Solution

Thermally expandable microspheres are created using a copolymer of itaconate dialkylesters and aliphatic or aromatic mono-ethylenically unsaturated comonomers, which meet the necessary requirements for encapsulating a blowing agent and expanding satisfactorily, with the copolymer containing 0-50 wt.% of vinyl aromatic comonomers and suitable alkyl groups, and the process involves aqueous suspension polymerization with a free-radical initiator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional petrochemical-based monomers are used to produce thermally expandable microspheres, then the microspheres achieve good expansion properties and thermoplastic shell performance, but the production has a high eco-footprint and is not sustainable

Engineering Contradiction:

Improveexpansion propertiesVSAvoideco-footprint

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the chemical composition parameters of the monomers from petrochemical-based to bio-based sources while adjusting the copolymer composition to maintain 0-50 wt.% vinyl aromatic comonomers, achieving both sustainability and functional performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite polymer system combining bio-based itaconate dialkylester with conventional vinyl aromatic comonomers, merging the sustainability benefits of bio-based materials with the proven performance characteristics of conventional monomers

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If bio-based monomers are used to replace conventional monomers, then the eco-footprint is reduced, but the polymer shell fails to meet surface energy, gas barrier, and viscoelastic property requirements

Engineering Contradiction:

Improveeco-footprintVSAvoidpolymer shell performance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The invention forms a composite copolymer combining bio-based itaconate dialkylester with vinyl aromatic comonomers, where the combination achieves the required surface energy for core-shell particle formation, gas barrier properties for blowing agent retention, and viscoelastic properties for expansion

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention optimizes the compositional parameters of the copolymer, specifically controlling the vinyl aromatic comonomer content at 0-50 wt.%, to achieve the precise balance of surface energy, gas barrier, and viscoelastic properties needed for functional expandable microspheres

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a polymer is formed to meet surface energy requirements for core-shell particle formation, then encapsulation of blowing agent is achieved, but the polymer may lack sufficient gas barrier properties to retain the blowing agent

Engineering Contradiction:

Improvecore-shell particle formationVSAvoidblowing agent retention

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The copolymer combines itaconate dialkylester components that facilitate core-shell particle formation with vinyl aromatic comonomers that provide excellent gas barrier properties, achieving both ease of manufacture and blowing agent retention

Inventive Principle:

Principle #40Composite materials

4Reliability

If the polymer shell is designed for good expansion properties, then the microspheres expand satisfactorily when heated, but the polymer may have insufficient viscoelastic properties above glass transition temperature

Engineering Contradiction:

Improveexpansion propertiesVSAvoidviscoelastic properties

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention adjusts the copolymer composition parameters and controls the vinyl aromatic comonomer content to optimize the glass transition temperature and viscoelastic behavior, ensuring the shell becomes sufficiently soft and stretchable at expansion temperatures while maintaining structural integrity

Inventive Principle:

Principle #35Parameter changes

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 bio-based thermally expandable microspheres exhibit good expansion properties, retaining the blowing agent and having a reduced eco-footprint, suitable for high-temperature applications like foaming in extrusion or injection molding processes.

Implementation Method 1

aqueous suspension polymerization of ethylenically unsaturated monomer(s) using a free-radical initiator

Methodology Applied

Scientific EffectFree-radical polymerization: Photopolymerisation

Implementation Method 2

Upon heating the thermoplastic shell softens

Methodology Applied

Scientific EffectThermal softening: Heating

Implementation Method 3

the blowing agent volatilizes while being retained within the thermoplastic shell

Methodology Applied

Scientific EffectVolatilization: Evaporation

Implementation Method 4

a blowing agent (propellant) encapsulated therein

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Data Source

PatentEP3713664B1Thermally expandable microspheres prepared from bio-based monomers

Publication Date: 2022.01.05 AKZO NOBEL CHEMICALS INTERNATIONAL BV

AI summary

The present invention relates to thermally expandable microspheres at least partially prepared from bio-based monomers and to a process of their manufacture. The microspheres comprise a thermoplastic polymer shell encapsulating a blowing agent, wherein the thermoplastic polymer shell comprises a copolymer of an itaconate dialkylester and at least one aliphatic or aromatic mono-ethylenically unsaturated comonomer, wherein the itaconate dialkylester is according to formula (1): wherein each of R1 and R2, separately from one another,isan alkyl group preferably with 1-4 carbon atoms, and wherein the copolymer contains 0-50 wt.% of vinyl aromatic comonomers, based on the total weight of the comonomers. The invention further provides expanded microspheres, which can be used in a variety of applications.