Thermoplastic Copolyester Foams for Low-Density, Crack-Free Cells

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Solution Overview

Problem

Existing foamed compositions suffer from high densities and plasticizer leaching, and often exhibit cracks due to cell wall overstretching, which are undesirable in lightweight applications.

Innovation Solution

A foamed composition comprising a thermoplastic copolyester elastomer with a relative solution viscosity (RSV) of at least 4.1, composed of polyester repeating units from aliphatic diol and aromatic dicarboxylic acid, and soft segments of polytetramethylene oxide, is prepared using a solid state post condensation process to minimize cracks and reduce plasticizer use.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If conventional foamed compositions are used to achieve low density, then weight is reduced, but cracks form due to cell wall overstretching

Engineering Contradiction:

ImprovedensityVSAvoidcrack formation

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters by using specific polyester repeating units (from aliphatic diol and aromatic dicarboxylic acid) combined with polytetramethylene oxide in a copolyester elastomer system. This compositional parameter change enables the material to achieve low density while preventing crack formation through improved cell wall integrity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite thermoplastic copolyester elastomer system combining hard segments (from polyester repeating units) and soft segments (polytetramethylene oxide). This composite structure provides both the necessary flexibility for low density and the structural integrity to prevent cracks during foaming.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If plasticizer is added to improve processing properties, then ease of manufacture is improved, but plasticizer leaching occurs

Engineering Contradiction:

Improveprocessing propertiesVSAvoidplasticizer leaching

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

The patent extracts and eliminates the need for separate plasticizer additives by incorporating plasticizing functionality directly into the copolyester elastomer structure itself. The copolyester composition provides processing properties without requiring external plasticizers that would subsequently leak out.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The copolyester elastomer serves multiple functions simultaneously: it provides structural integrity, enables low density foaming, and delivers processing properties traditionally requiring separate plasticizers. This multi-functional material eliminates the need for additional plasticizer components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Strength

If high density foamed compositions are used, then structural integrity is improved, but weight increases

Engineering Contradiction:

Improvestructural integrityVSAvoiddensity

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent changes the molecular weight and compositional parameters of the copolyester elastomer to optimize the balance between structural integrity and density. By adjusting the ratio of hard to soft segments and the molecular architecture, the material achieves sufficient strength at low densities.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates local quality differentiation within the foam structure through the copolyester elastomer's segmented structure. The hard segments provide localized structural reinforcement while the soft segments provide flexibility and low density, creating an optimal local composition that prevents both cracks and excessive weight.

Inventive Principle:

Principle #3Local quality

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 low-density, crack-free foams suitable for lightweight applications by maintaining the integrity of cell structures, enabling lower plasticizer content and improved processing properties.

Implementation Method 1

a thermoplastic copolyester elastomer, wherein the thermoplastic copolyester elastomer comprises hard segments built up from polyester repeating units derived from at least one aliphatic diol and at least one aromatic dicarboxylic acid or an ester thereof and soft segments being polytetramethylene oxide

Methodology Applied

Scientific EffectPhase separation:

Implementation Method 2

hard segments built up from polyester repeating units derived from at least one aliphatic diol and at least one aromatic dicarboxylic acid or an ester thereof

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Data Source

PatentUS12404402B2Foamed composition

Publication Date: 2025.09.02 ENVALIOR BV

AI summary

The invention relates to a foamed composition comprising a thermoplastic copolyester elastomer, wherein the foamed composition has a relative solution viscosity of at least 4.1 as measured according to ISO 1628-5:2015 and wherein the thermoplastic copolyester elastomer comprises hard segments built up from polyester repeating units derived from at least one aliphatic diol and at least one aromatic dicarboxylic acid or an ester thereof and soft segments being polytetramethylene oxide. The invention also relates to a process for preparing the foamed composition.