Polyester Film Crystallinity Control for Uniform Shrinkage
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Solution Overview
Problem
Conventional polyester films used in heat shrinkage processes exhibit fast shrinkage speed and high shrinkage stress, leading to non-uniform shrinkage and distortions in plastic containers, and pose challenges in recycling due to high crystallinity and residual ink issues, resulting in low recyclability and environmental pollution.
Innovation Solution
A polyester film with controlled crystallinity, achieved by copolymerizing diol and dicarboxylic acid to set the crystallization temperature between 70° C. to 130° C., allowing for a low clumping ratio when thermally treated, and a process for regenerating polyethylene terephthalate containers without separating the film, enhancing recyclability and quality of regenerated chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional polyester film is used for heat shrinkage packaging, then thermal resistance and weatherability are improved, but shrinkage uniformity deteriorates due to fast shrinkage speed and high shrinkage stress
Solution Approach 1:
The patent changes the crystallinity parameter of polyester film from conventional high crystallinity (30-40%) to low crystallinity (5-20%). This parameter change slows down the shrinkage speed and reduces shrinkage stress, allowing the film to shrink uniformly without causing distortion to the container, while maintaining adequate thermal resistance for heat shrinkage processing
Solution Approach 2:
The patent uses composite polyester resin comprising multiple polyester components with different crystallinities (first polyester resin with 10-30% crystallinity and second polyester resin with 30-50% crystallinity). This composite structure balances the contradictory requirements by combining the low crystallinity component for uniform shrinkage with the higher crystallinity component for thermal resistance
2Temperature
If polyester film with high crystallinity is used, then thermal resistance is improved, but recyclability deteriorates due to clumping during thermal treatment
Solution Approach 1:
The patent changes the crystallinity parameter to low range (5-20%), which fundamentally alters the thermal behavior of the polyester film during recycling. This parameter change prevents clumping during thermal treatment at 210°C for 90 minutes, as the lower crystallinity reduces the tendency of polymer chains to aggregate and form clumps, thereby enabling effective recycling with clumping ratio of 10% or less
3Manufacturing precision
If polyester elastomer is added to suppress wrinkles and distortions, then shrinkage uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent achieves shrinkage uniformity by changing the crystallinity parameter of the base polyester resin to low range (5-20%), eliminating the need to add polyester elastomer components. This approach maintains film composition simplicity while achieving the desired shrinkage performance, as the low crystallinity itself provides slow and uniform shrinkage behavior
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 exhibits improved shrinkage characteristics and seaming properties with reduced clumping, enhancing the recyclability and quality of regenerated polyester chips, while preventing environmental pollution and saving time and cost in the regeneration process.
Implementation Method 1
a copolymerized polyester resin in which a diol and a dicarboxylic acid are copolymerized
Implementation Method 2
the crystallization temperature (Tc) of the film is not measured or is 70° C. to 130° C. by differential scanning calorimetry
Implementation Method 3
when the flakes obtained by crushing a polyethylene terephthalate (PET) container provided with the polyester film are thermally treated at a temperature of 210° C. for 90 minutes, the clumping ratio is 10% or less
Implementation Method 4
a heat shrinkable film is cut, printed in a desired design, rolled up, bonded at both ends with an adhesive solvent, loosely wrapped around a container, and then shrunk as heat is applied thereto
Data Source
AI summary
Embodiments relate to a polyester film, preparation method thereof and method for reproducing polyethyleneterephthalate (PET) container using same, the crystallization temperature (Tc) of the polyester film is not measured or is 70° C. to 130° C., as measured by differential scanning calorimetry, whereby it is possible to easily control the crystallinity. Accordingly, the polyester film has excellent shrinkage characteristics and recyclability, and clumping rarely occurs even if it is dried at high temperatures for a long period of time in the regeneration process.