Polyester Coating Electron Beam Radiation Heat-Sealability

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Solution Overview

Problem

Polyesters, particularly polylactide, face challenges in heat-sealability due to high melting temperatures and poor adhesion to fibrous substrates, making them difficult to use as a surface layer in packaging, and existing solutions either require expensive additives or additional processing steps or have limited effectiveness.

Innovation Solution

Subjecting polyester coatings to electron beam (EB) radiation to lower melt viscosity and improve heat-sealability, avoiding catalysts that promote cross-linking, and combining with other treatments like UV radiation and flame treatment to enhance adhesion and reduce heat-sealing temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polylactide is used as a coating material, then biodegradability and barrier properties are improved, but heat-sealability deteriorates due to high melting temperature

Engineering Contradiction:

ImprovebiodegradabilityVSAvoidheat-sealability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies electron beam radiation to change the physical-chemical parameters of polylactide, specifically reducing melt viscosity and lowering the effective heat-sealing temperature range, thereby improving heat-sealability while maintaining biodegradability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces conventional thermal processing methods with electron beam radiation processing to achieve the desired polymer chain scission and viscosity reduction, enabling heat-sealing at lower temperatures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If polylactide is used as a coating material, then barrier properties are improved, but adhesion to fibrous substrate deteriorates

Engineering Contradiction:

Improvebarrier propertiesVSAvoidadhesion to substrate

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

Electron beam radiation modifies the surface and bulk properties of polylactide, creating functional groups and reducing crystallinity that enhance adhesion to fibrous substrates while preserving water vapour and gas barrier properties

Inventive Principle:

Principle #35Parameter changes

3Temperature

If polyethylene terephthalate is used as coating material, then heat-resistance is improved, but heat-sealability deteriorates

Engineering Contradiction:

Improveheat-resistanceVSAvoidheat-sealability

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent applies electron beam radiation to PET coating materials to reduce melt viscosity and lower the heat-sealing temperature range, enabling effective heat-sealing while maintaining the inherent heat-resistance and barrier properties of PET

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If polylactide is blended with other polyesters to improve heat-sealability, then heat-sealability is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improveheat-sealabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the need for polymer blending by using electron beam radiation to directly modify polylactide properties, simplifying the manufacturing process to a single-step radiation treatment instead of multi-component blending and processing

Inventive Principle:

Principle #2Taking out (Extraction)

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

EB radiation significantly improves heat-sealability by reducing melt viscosity and heat-sealing temperatures, eliminating the need for additional adhesion layers and costly additives, while maintaining biodegradability and enhancing adhesion to fibrous substrates, allowing for cost-effective manufacturing of heat-sealed containers and packages.

Implementation Method 1

subjecting polyester to electron beam (EB) radiation. There is thus provided a novel method of lowering the melt viscosity of polyester

Methodology Applied

Scientific EffectElectron beam radiation: Electron Beam

Implementation Method 2

EB radiation significantly improves heat-sealability by reducing melt viscosity

Methodology Applied

Scientific EffectChain scission:

Implementation Method 3

WO 2011/135182, which teaches ultraviolet (UV) radiation of a polyester layer to improve its heat-selability

Methodology Applied

Scientific EffectUltraviolet radiation:

Implementation Method 4

combining with other treatments like UV radiation and flame treatment to enhance adhesion

Methodology Applied

Scientific EffectFlame treatment:

Data Source

PatentEP3097143B1Methods for lowering melt viscosity and improving heat-sealability of polyester and for manufacturing a heat-sealed container or package

Publication Date: 2020.03.11 STORA ENSO OYJ

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AI summary

The invention relates to methods for lowering the melt viscosity and thereby improving heat-sealability of a polyester. The invention also relates to a method for manufacturing a heat-sealed container or package from fibrous- based, polyester-coated packaging material, and a method for heat-sealing polyester. The solution according to the invention is subjecting polyester to electron beam (EB) radiation. The lowered melt viscosity allows a lower heat- sealing temperature, and permits sealing of polyester to an uncoated fibrous surface. The preferred polyester for the invention is polylactide, as such or as blended with another polyester.