UV Treatment for Polylactide Heat Sealability

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Solution Overview

Problem

Polylactide and other biodegradable polyester films in packaging materials face challenges with poor heat sealability due to high melting temperatures and require expensive additives or complex blending processes, while conventional heat-sealing methods are inefficient for materials like PET.

Innovation Solution

Ultraviolet radiation is applied to the polyester layer of packaging materials, reducing the heat-sealing temperature required for polylactide and its blends to levels comparable to low-density polyethylene, allowing for improved heat sealability without the need for additional adhesives or costly additives.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polylactide is used in packaging 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 invention changes the physical-chemical parameters of polylactide by subjecting it to ultraviolet radiation, which modifies its molecular structure and lowers the heat-sealing temperature from above 100°C to levels comparable with LDPE, thereby improving heat sealability while maintaining biodegradability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the conventional thermal modification method with ultraviolet radiation treatment. Instead of using heat or chemical additives to modify polylactide, UV radiation is applied to achieve the desired lowering of heat-sealing temperature, providing a more efficient and cost-effective solution

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Temperature

If conventional heat-sealing methods are used on PET films, then heat resistance is maintained, but heat sealability deteriorates

Engineering Contradiction:

Improveheat resistanceVSAvoidheat sealability

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The invention changes the physical-chemical parameters of PET by applying ultraviolet radiation, which modifies the polymer structure to enable heat sealing at lower temperatures while preserving the material's inherent heat resistance properties for its intended application

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If expensive additives or polymer blending is used to improve heat sealability, then heat sealability is improved, but manufacturing cost increases

Engineering Contradiction:

Improveheat sealabilityVSAvoidmanufacturing cost

Core Design Contradiction:

Ease of manufactureVSQuantity of substance

Solution Approach 1:

The invention extracts the need for expensive additives and complex blending processes by using ultraviolet radiation to directly modify the polylactide or PET material. This eliminates additional material costs and simplifies the manufacturing process while achieving the desired heat sealability improvement

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention enables the packaging material to self-modify its heat-sealing properties through ultraviolet radiation treatment. The material itself undergoes structural changes that improve heat sealability without requiring external additives or complex processing steps

Inventive Principle:

Principle #25Self-service

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

UV radiation significantly lowers the heat-sealing temperature for polylactide and its blends, enhancing seal strength and reducing processing costs, while maintaining biodegradability and barrier properties, and improving sealability of PET films.

Implementation Method 1

Ultraviolet radiation is applied to the polyester layer of packaging materials, reducing the heat-sealing temperature required for polylactide and its blends

Methodology Applied

Scientific EffectUltraviolet radiation: Radiation

Data Source

PatentUS10857753B2Method for improving the heat sealability of packaging material and method for manufacturing heat-sealed container or package

Publication Date: 2020.12.08 STORA ENSO OYJ

AI summary

A method for improving the heat sealability of a packaging material and a method for manufacturing a heat-sealed container or package are described. The material can be polymer-coated packaging paper or cardboard, or a polymeric packaging film. The material includes a polymer layer that contains polyester, particularly polylactide, the heat sealability of which is improved by ultraviolet radiation. Polylactide is useful as such or when blended, for example, with other biodegradable polyester. The containers and packages thus manufactured include disposable drinking cups and cardboard carton and box packages.