Heat-shrinkable Polyester Film with Low Amorphous Content
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Solution Overview
Problem
Conventional heat-shrinkable polyester films have limitations in mechanical strength, surface flaws, and environmental sustainability due to high amorphous component content, which affects their shrinkage characteristics and recyclability.
Innovation Solution
A heat-shrinkable polyester film with a main component of ethylene terephthalate, containing not more than 5 mol% amorphous component, exhibiting specific shrinkage rates, low orientation distortion, and minimal surface flaws, produced through controlled biaxial stretching without heating above the film's Tg.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common heat-shrinkable polyester films use a large quantity of amorphous component monomer to provide shrinkage characteristics, then shrinkage performance is improved, but mechanical strength deteriorates and surface flaws increase
Solution Approach 1:
The patent changes the chemical composition parameters by limiting amorphous component content to 5 mol% or less and using specific crystalline polyester resins with controlled intrinsic viscosity (0.6-1.0 dl/g). This parameter optimization allows achieving shrinkage characteristics through controlled crystallization rather than relying on high amorphous content, thereby maintaining mechanical strength while providing reliable shrinkage performance.
Solution Approach 2:
The patent creates a composite structure by combining crystalline polyester resin with specific additives (nucleating agents, plasticizers) in controlled amounts. This composite approach enables the film to achieve shrinkage characteristics through the synergistic effect of crystalline phases and additives, rather than relying solely on amorphous components, thus improving both shrinkage reliability and mechanical strength.
2Reliability
If common heat-shrinkable polyester films use a large quantity of amorphous component monomer, then shrinkage characteristics are improved, but surface quality deteriorates due to increased flaws
Solution Approach 1:
The patent optimizes composition parameters by limiting amorphous component content to 5 mol% or less and controlling crystalline resin properties (intrinsic viscosity 0.6-1.0 dl/g). This reduces the formation of surface flaws during processing while maintaining shrinkage characteristics through controlled crystallization, thereby improving surface quality without sacrificing shrinkage reliability.
3Reliability
If films are stretched at high ratio in width direction to develop shrinkage characteristics, then shrinkage performance in width direction is improved, but mechanical strength in lengthwise direction deteriorates
Solution Approach 1:
The patent changes the approach by controlling the degree of crystallinity and molecular orientation through specific stretching ratios and heat treatment conditions. By using crystalline polyester resin with controlled intrinsic viscosity and applying biaxial stretching with subsequent heat treatment, the film develops shrinkage characteristics through crystallization rather than relying on extreme orientation, thereby maintaining mechanical strength in the lengthwise direction while providing adequate shrinkage performance.
4Reliability
If films containing large quantity of amorphous component are used, then shrinkage characteristics are improved, but recyclability deteriorates due to limited recycled raw material mixing ratio
Solution Approach 1:
The patent changes the compositional parameters by using primarily crystalline polyester resin with minimal amorphous component content (5 mol% or less). This composition is compatible with recycled PET materials, allowing high proportions of recycled content to be incorporated while maintaining shrinkage characteristics through controlled crystallization. This enables both shrinkage reliability and recyclability to be achieved simultaneously.
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 film achieves high mechanical strength, reduced surface flaws, and increased recyclability, enabling efficient fitting and appearance on containers with minimal distortion and wrinkles, while allowing for high recycled content usage.
Implementation Method 1
the film is stretched in a width direction and thereafter stretched in a lengthwise direction
Implementation Method 2
the heat-shrinkable polyester film has a hot-water heat shrinkage rate in the lengthwise direction of not less than 15% and not more than 60% when being treated in hot water at 90° C. for 10 seconds
Data Source
AI summary
A heat-shrinkable polyester film comprising ethylene terephthalate as a main component, containing not less than 0 mol % and not more than 5 mol % of a monomer component capable of serving as an amorphous component relative to the total of a polyester resin component, and having a main shrinkage direction in a lengthwise direction, wherein the heat-shrinkable polyester film satisfies heat shrinkage characteristics of the width direction and the lengthwise direction and the molecular orientation angle difference which is a difference between a molecular orientation angle of an edge of one end in the width direction and a molecular orientation angle of an edge of the other end.