Heat-Shrinkable Polyester Film for Thin Labels With Drop Resistance
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Solution Overview
Problem
Existing heat-shrinkable polyester-based films used for PET bottle labels face issues with reduced thickness leading to bag-drop resistance and stiffness, resulting in label tearing and attaching failures, while existing solutions require complex biaxial drawing facilities.
Innovation Solution
A heat-shrinkable polyester-based film with specific composition and properties, including 60-95% ethylene terephthalate units, 5-40% diethylene glycol, and controlled shrinkage ratios and puncture strength, produced through uniaxial drawing in the width direction to enhance bag-drop resistance and stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the film thickness is reduced to decrease waste and weight, then the amount of waste and weight are reduced, but the bag-drop resistance and stiffness deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the polyester resin by controlling the molar ratio of ethylene glycol to diethylene glycol (within 0.3 to 1.5) and the intrinsic viscosity (within 0.60 to 1.00 dl/g). These parameter changes enable the film to achieve both reduced thickness (15-35 μm) and maintained/high puncture strength, resolving the contradiction between thinness and bag-drop resistance
Solution Approach 2:
The patent creates a composite polyester resin system combining ethylene glycol and diethylene glycol in specific proportions, along with controlled crystallinity (30-70%). This composite material approach allows the film to achieve optimal balance between flexibility, stiffness, and puncture strength at reduced thickness, improving both waste reduction and reliability
2Volume of moving object
If the film thickness is reduced for volume reduction, then the volume is reduced, but the stiffness is lowered causing label bending and attaching failure
Solution Approach 1:
The patent controls specific parameters including intrinsic viscosity (0.60-1.00 dl/g) and crystallinity (30-70%) of the polyester resin. These parameter changes enable the film to maintain adequate stiffness for label attachment while achieving reduced thickness (15-35 μm) for volume reduction, preventing label bending during attachment
3Strength
If biaxial drawing is used to improve label strength in the non-shrinkage direction, then the label strength is improved, but the facility becomes long and complex
Solution Approach 1:
The patent extracts the longitudinal drawing step from the biaxial drawing process, using only width-direction (lateral) drawing. The resin composition and crystallinity control compensate for the missing longitudinal drawing, maintaining label strength without requiring complex biaxial drawing facilities, thus simplifying the production line
Solution Approach 2:
The patent changes the resin parameters (intrinsic viscosity 0.60-1.00 dl/g, crystallinity 30-70%) to achieve the desired mechanical properties without biaxial drawing. This parameter optimization allows uniaxial drawing to suffice, reducing facility complexity while maintaining label strength in both directions
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 shrinkage ratios with improved puncture strength and stiffness, reducing bag breakage and attaching failures, even when dropped, using simpler production equipment.
Implementation Method 1
a hot water heat shrinkage ratio in the film width direction is 40% or more and 80% or less when the film is immersed in hot water at 90° C. for 10 seconds
Data Source
AI summary
The invention provides a heat-shrinkable polyester-based film which has a high heat shrinkage ratio in the main shrinkage direction, as well as a high film puncture strength, bag breakage resistance upon bottle dropping, and excellent stiffness because of the high density of the film. The heat-shrinkable polyester-based film contains 60-95 mol % ethylene terephthalate units in 100 mol % of all ester units, 5-40 mol % diethylene glycol in 100 mol % of the polyhydric alcohol component, and 0-5 mol % constituent units derived from a monomer component that can be an amorphous component in all polyester resin components, in which the hot water heat shrinkage ratio, the puncture strength of the film, the density of the film, and the refractive index in the longitudinal direction of the film are within predetermined ranges when the film is immersed in hot water at 90° C. for 10 seconds.