Halogen-Free Thermally Expandable Microspheres with Low Expansion Temperature

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Solution Overview

Problem

Thermally expandable microspheres containing halogenated monomers, such as VDC, face sustainability and health concerns due to high halogen content, and halogen-free alternatives require high expansion temperatures, leading to storage stability issues and increased energy demands.

Innovation Solution

Developing thermoplastic thermally expandable microspheres with polymer shells composed of acrylonitrile, methacrylonitrile, and methyl acrylate/methyl methacrylate, free from halogen-containing monomers, which can be expanded at lower temperatures and maintain excellent barrier and storage stability, even in a wet state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If halogen-free monomers are used to replace halogenated monomers, then sustainability and health safety are improved, but expansion temperature increases and storage stability deteriorates

Engineering Contradiction:

Improvehalogen contentVSAvoidexpansion temperature

Core Design Contradiction:

Object-affected harmful factorsVSTemperature

Solution Approach 1:

The patent uses a composite monomer system comprising acrylonitrile (40-70 wt%), methacrylonitrile (10-30 wt%), and methyl acrylate or methyl methacrylate (10-30 wt%). This composite approach combines the benefits of different monomers: acrylonitrile provides barrier properties, methacrylonitrile enhances structural integrity, and methyl acrylate/methacrylate reduces glass transition temperature for lower expansion temperature, all while maintaining halogen-free composition and improving storage stability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes the compositional parameters of the monomer mixture to achieve the desired balance. By adjusting the weight percentages of each monomer within specific ranges and controlling the propellant content (5-20 wt%), the polymer shell achieves optimal glass transition temperature and barrier properties, enabling lower expansion temperature while maintaining storage stability in halogen-free microspheres.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If halogen-free monomers are used to replace halogenated monomers, then sustainability and health safety are improved, but storage stability deteriorates

Engineering Contradiction:

Improvehalogen contentVSAvoidstorage stability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The composite monomer system with acrylonitrile, methacrylonitrile, and methyl acrylate/methacrylate creates a polymer shell with enhanced structural integrity and barrier properties. This composite structure prevents propellant diffusion and maintains microsphere stability during storage, resolving the storage stability issue associated with halogen-free alternatives.

Inventive Principle:

Principle #40Composite materials

3Reliability

If high expansion temperature is used for halogen-free microspheres, then barrier properties are maintained, but energy consumption increases

Engineering Contradiction:

Improvebarrier propertiesVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

By modifying the polymer shell composition to include methyl acrylate or methyl methacrylate (10-30 wt%), the glass transition temperature is reduced, allowing expansion to occur at lower temperatures (below 100°C). This parameter change maintains barrier properties through optimized monomer ratios while significantly reducing the energy consumption required for expansion.

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 microspheres achieve excellent barrier properties and long-term storage stability without halogen content, enabling flexible expansion at lower temperatures and improved handling characteristics.

Implementation Method 1

a polymer shell formed from ethylenically unsaturated monomers and encapsulates the propellant

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Implementation Method 2

the propellant vaporizes and expands, thus expanding the microsphere

Methodology Applied

Scientific EffectVaporization: Evaporation

Implementation Method 3

the propellant vaporizes and expands, thus expanding the microsphere

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 4

the thermoplastic polymeric shell softens, and the propellant vaporizes and expands

Methodology Applied

Scientific EffectSoftening: Melting

Data Source

PatentUS20240360291A1Expanded microspheres with excellent barrier properties

Publication Date: 2024.10.31 AKZO NOBEL CHEMICALS INTERNATIONAL BV

AI summary

Thermoplastic thermally expandable microspheres comprise a polymer shell and a propellant, wherein the polymer shell is formed from ethylenically unsaturated monomers and encapsulates the propellant, and wherein the ethylenically unsaturated monomers comprise acrylonitrile in an amount from 45 to 80 weight %, methacrylonitrile in an amount of from 10 to 45 weight %, and methyl acrylate and/or methyl methacrylate in an amount of 5 to 35 weight %, each based on the total weight of ethylenically unsaturated monomers, and wherein the thermoplastic thermally expandable microspheres comprise the propellant in an amount of 5 to 17 weight %, based on the total weight of the thermoplastic thermally expandable microspheres. The thermoplastic thermally expandable microspheres are formed in a process of the disclosure and may be present in an aqueous slurry.