Crystallizable Polyester Shrink Films for PET Recycling
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Solution Overview
Problem
Current polyester shrink films used in packaging with PET bottles face issues such as clumping during recycling due to softening at high temperatures, which reduces PET flake yield and requires additional handling steps, and lack recyclability, impacting the recycling process.
Innovation Solution
Development of crystallizable polyester blends comprising specific combinations of terephthalic acid, neopentyl glycol, 1,4-cyclohexanedimethanol, ethylene glycol, and diethylene glycol, which maintain structural integrity at high temperatures and can be recycled without forming clumps, allowing for seamless integration into PET recycling streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If typical polyester shrink film resins are used, then the film provides good shrink film performance, but the film softens and becomes sticky at high temperatures during recycling, creating clumps with PET flakes and reducing PET flake yield
Solution Approach 1:
The patent changes the chemical composition parameters of the polyester resin by incorporating specific ratios of glycol monomers (ethylene glycol, diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol) to modify the thermal properties. This creates a crystallizable polyester blend that maintains structural integrity at high temperatures during recycling while preserving shrink film performance, preventing clumping with PET flakes.
Solution Approach 2:
The patent creates a composite polyester material by blending multiple polyester compositions with different properties. The blend includes crystallizable polyester components that provide high-temperature stability and amorphous components that provide shrink film performance. This composite structure allows the film to function as a shrink wrap while being compatible with PET recycling processes.
2Reliability
If typical polyester shrink film resins are used, then the film provides adequate shrinkage properties, but additional handling steps are required to remove clumps during recycling
Solution Approach 1:
The patent modifies the thermal and structural parameters of the polyester resin through controlled composition of glycol monomers. The resulting crystallizable polyester blend maintains its shape and does not soften excessively at recycling temperatures, eliminating the need for separate handling steps to remove clumps. The film can be processed with PET flakes through standard recycling procedures.
3Reliability
If the shrink film label is made from non-recyclable materials, then the label provides good shrink film performance, but the entire bottle cannot be recycled without creating additional handling requirements
Solution Approach 1:
The patent changes the chemical composition parameters of the shrink film resin to match the recyclability requirements of PET. By using a crystallizable polyester blend with specific glycol monomer ratios, the film maintains compatibility with PET recycling processes, allowing the entire bottle including label to be recycled together without additional handling requirements.
Solution Approach 2:
The patent creates a shrink film material that serves dual functions: it provides the necessary shrink wrap performance for packaging while being compatible with PET recycling processes. This universal material can be used on PET bottles and processed through standard PET recycling facilities, eliminating the need for separate handling of non-recyclable labels.
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 crystallizable polyester blends ensure efficient recycling by preventing clumping and maintaining film integrity, enabling the entire bottle, including the label, to be recycled without additional handling or environmental issues, thus enhancing recycling efficiency and reducing waste.
Implementation Method 1
they have high strain induced crystalline melting points, so they provide superior performance in recycling processes
Implementation Method 2
PET is dried at temperatures above 200° C.
Data Source
AI summary
The present disclosure relates to crystallizable shrinkable films and thermoformable film(s) or sheet(s) comprising blends of polyester compositions which comprise residues of terephthalic acid, neopentyl glycol (NPG), 1,4-cyclohexanedimethanol (CHDM), ethylene glycol (EG), and diethylene glycol (DEG), in certain compositional ranges having certain advantages and improved properties.