Amorphous Copolymerized Polyester Film for Heat-Shrinkable Labels
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Solution Overview
Problem
Heat-shrinkable polyester films exhibit high natural shrinking rates and significant changes in shrinking rates after aging, leading to inadequate finishing and distortion when used in packaging applications, especially with low heat transfer coefficient hot air systems.
Innovation Solution
An amorphous copolymerized polyester film with specific composition and processing conditions, including 18-30% neopentyl glycol, 8-16% diethylene glycol, intrinsic viscosity of 0.70-0.86 dl/g, and melt viscosity of 200 Pa·S or less, which maintains high heat-shrinking rates and low natural shrinking rates even after aging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the shrinking rate is adjusted to be high to deal with various containers, then the heat-shrinking performance is improved, but the natural shrinking rate increases and the heat-shrinking rate at 70°C decreases after aging
Solution Approach 1:
The invention changes the chemical composition parameters of the polyester by controlling the molar ratios of specific glycols (18-30% neopentyl glycol, 8-16% diethylene glycol) and adjusting intrinsic viscosity (0.68-0.85 dl/g) and melt viscosity (≤200 Pa·S at 250°C). These parameter changes enable the film to achieve high heat-shrinking rate (60-85% at 98°C) while maintaining stable natural shrinking rate (≤0.5%) and consistent heat-shrinking performance at 70°C even after aging
Solution Approach 2:
The invention uses a composite polyester structure formed by copolymerization of multiple glycol components (ethylene glycol, neopentyl glycol, diethylene glycol, and 1,4-cyclohexanedimethanol) with terephthalic acid. This composite material approach creates a balanced molecular structure that provides both high heat-shrinking capability and dimensional stability after aging, resolving the contradiction between shrinkage performance and natural shrinking control
2Speed
If the shrinking rate is adjusted to be high to deal with various containers, then the heat-shrinking performance is improved, but the finish after shrinking becomes bad due to distortion and insufficient shrinking
Solution Approach 1:
By optimizing the viscosity parameters (intrinsic viscosity 0.68-0.85 dl/g and melt viscosity ≤200 Pa·S at 250°C) and compositional parameters (specific glycol ratios), the invention ensures uniform heat distribution and consistent shrinking behavior during hot air processing. This results in excellent finish after shrinking with minimal distortion and uniform coverage, even when dealing with various container geometries
3Speed
If the initial shrinking rates by hot air are different before and after aging, then the heat-shrinking performance varies, but consistent processing becomes difficult
Solution Approach 1:
The invention modifies the polyester's molecular structure parameters (intrinsic viscosity 0.68-0.85 dl/g, specific glycol composition) to create a material where the physical and chemical properties remain stable before and after aging. This ensures that the initial shrinking rate by hot air remains consistent, enabling reliable and repeatable processing results throughout the product's storage life
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 stable and high heat-shrinking performance with minimal size change and wrinkle formation, ensuring consistent processing and appearance in packaging, even after long storage, and is suitable for a broader range of container sizes.
Implementation Method 1
a heat-shrinkable polyester-based film which exhibits high heat resistance... a film which greatly shrinks in a widthwise direction... a film which stretches by heating
Data Source
AI summary
The invention provides an amorphous copolymerized polyester raw material for a film. The raw material contains ethylene terephthalate as a main constituent component, and contains from 18% by mol to 30% by mol of neopentyl glycol when a total amount of a glycol component in a total polyester resin component is taken as 100% by mol. The raw material contains from 8% by mol to 16% by mol of a constituent unit derived from diethylene glycol in the total amount (100% by mol) of the glycol component in the total polyester resin component. The raw material has an intrinsic viscosity of from 0.70 dl/g to 0.86 dl/g. The raw material has a melt viscosity of 200 Pa·S or less, when measured at a shear rate of 6080/S at 250° C.