Heat-Shrinkable Polyester Film Composition for Shrinkage Stress and Aging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing heat-shrinkable polyester films face issues with high shrinkage stress leading to label peeling and container deformation, and decreased tensile elongation over time due to hydrolysis and aging, which complicates post-processing and affects film functionality.
Innovation Solution
A heat-shrinkable polyester film with specific composition and manufacturing process, including ethylene terephthalate as the main component, diethylene glycol content between 6-25 mol%, and optimized planar orientation, ensuring high heat shrinkage, low shrinkage stress, and maintained tensile elongation even after aging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the shrinkage stress is increased to improve heat shrinkage performance, then the heat shrinkage is improved, but the label peeling and container deformation occur
Solution Approach 1:
The patent changes the chemical composition parameters of the polyester film by controlling the content of diethylene glycol (6-25 mol%) and other polyhydric alcohols to achieve optimal balance between shrinkage stress and adhesion strength. This parameter optimization allows the film to maintain sufficient heat shrinkage while preventing label peeling during the shrinking process.
2Temperature
If the shrinkage stress is increased to improve heat shrinkage performance, then the heat shrinkage is improved, but the container deformation occurs
Solution Approach 1:
The patent optimizes the polyester composition parameters, specifically controlling diethylene glycol content at 6-25 mol% and limiting other polyhydric alcohols to 5-20 mol%, to achieve a balanced shrinkage stress that enables adequate heat shrinkage without causing container deformation. This compositional control ensures the film shrinks sufficiently while maintaining container shape integrity.
3Strength
If the tensile elongation is maintained to prevent film rupture during storage, then the film strength is improved, but the shrinkage performance may be reduced
Solution Approach 1:
The patent creates a composite polyester system combining ethylene terephthalate with specific ratios of diethylene glycol (6-25 mol%) and other polyhydric alcohols (5-20 mol%). This composite material structure simultaneously provides high tensile elongation to prevent film rupture during storage and maintains adequate heat shrinkage performance through the synergistic effect of the polymer components.
4Stress or pressure
If the diethylene glycol content is increased to improve shrinkage stress, then the shrinkage stress is reduced, but the tensile elongation decreases after aging
Solution Approach 1:
The patent precisely controls the diethylene glycol content parameter at 6-25 mol% and combines it with controlled amounts of other polyhydric alcohols (5-20 mol%). This dual-parameter control achieves the optimal balance where shrinkage stress is sufficiently reduced for good heat shrinkage performance while tensile elongation is maintained at 20% or more even after aging, preventing film rupture during post-processing.
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 maintains high heat shrinkage and low shrinkage stress, preventing label peeling and container deformation, while retaining tensile elongation over time, enhancing processing reliability and film functionality.
Implementation Method 1
it is known that the hydrolysis of polyester becomes easily proceed by containing a constituent unit derived from diethylene glycol, and reduced molecular weight by hydrolysis may cause decrease in tensile elongation
Implementation Method 2
a drawn film, so called heat-shrinkable film, composed of a polyvinyl chloride resin, a polystyrene resin, a polyester resin or the like has been widely used for both the label packaging of a glass bottle and a PET bottle
Data Source
AI summary
A heat-shrinkable polyester film that has (1) a hot-water heat shrinkage of 40% or more in a main shrinkage direction of the film when immersed in hot water of 98° C. for 10 seconds; (2) a planar orientation coefficient of 0.035-0.070; (3) ethylene terephthalate as a main constituent component and 6-25 mol % diethylene glycol (DEG) constituent in 100 mol % of polyhydric alcohol in all the polyester resin constituting the film; (4) a maximum shrinkage stress of 2-17 MPa in the main shrinkage direction of the film when measured in hot air of 90° C.; and (5) a tensile elongation at break of 20% or more in a direction orthogonal to the main shrinkage direction after the film is aged in an atmosphere with an atmospheric temperature of 40° C. and a relative humidity of 85% for 28 days.