Peelable Polyester Film for Meal Trays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing heat-sealable and peelable polyester films for APET and RPET menu trays face challenges in maintaining peelability at higher sealing temperatures, leading to dimensional instability and poor peeling behavior, while also requiring excellent optical properties and processability.
Innovation Solution
A transparent, biaxially oriented polyester film with a three-layer structure, comprising a base layer, a crosslinked acrylate coating layer, and a heat-sealable and peelable top layer made from 85-99% polyester and 1-15% other substances, specifically formulated to maintain medium peelability between 3 to 7 N/15mm, with a glass transition temperature between 0 and 30°C, and incorporating anti-fog agents and antiblocking particles for improved handling and clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher sealing temperatures (>135 to 150 °C) are used to improve sealability, then sealing quality improves, but dimensional stability deteriorates causing warping
Solution Approach 1:
The invention modifies the chemical composition parameters of the polyester film by incorporating specific amounts of cyclic carbonate units (5-50 mol%) and controlling the ratio of aromatic to aliphatic dicarboxylic acid units. This parameter change allows the material to maintain dimensional stability while achieving reliable sealing at elevated temperatures through molecular structure optimization rather than relying solely on temperature control.
Solution Approach 2:
The invention creates a composite polyester structure by combining different molecular units (aromatic dicarboxylic acid units, aliphatic dicarboxylic acid units, and cyclic carbonate units) within the same polymer matrix. This composite approach at the molecular level enables the material to simultaneously exhibit the heat resistance and dimensional stability of aromatic units while maintaining sealability through the flexible aliphatic and cyclic carbonate components.
2Reliability
If higher sealing temperatures are used to ensure sealability, then sealing reliability improves, but peelability deteriorates
Solution Approach 1:
The invention changes the chemical parameters of the polyester by introducing cyclic carbonate units (5-50 mol%) and controlling the composition ratio of different acid units. This modification creates a polymer structure with optimized thermal properties that maintains strong sealing adhesion at high temperatures while preserving cold-peelability through the specific molecular architecture that prevents excessive thermal degradation of the seal interface.
Solution Approach 2:
The invention applies local quality differentiation by having different molecular units perform different functions within the same polymer: aromatic units provide thermal stability for reliable sealing, while aliphatic units and cyclic carbonate units provide flexibility and cold-peelability. This spatial and functional differentiation at the molecular level resolves the contradiction between sealing strength and peelability.
3Productivity
If sealing time is reduced to less than one second for cost-effectiveness, then production efficiency improves, but sealing quality may deteriorate
Solution Approach 1:
The invention modifies the thermal response parameters of the polyester by incorporating cyclic carbonate units and optimizing the ratio of aromatic to aliphatic dicarboxylic acid units. This creates a material with enhanced heat transfer characteristics and lower melting point segments that enable rapid heating and sealing within one second or less, maintaining sealing quality while improving production efficiency.
Solution Approach 2:
The invention performs preliminary action by pre-optimizing the molecular structure during film production to include cyclic carbonate units and specific acid unit ratios. This pre-engineering of the polymer structure prepares the material in advance to respond rapidly to sealing heat, eliminating the need for extended sealing times and enabling fast sealing without compromising quality.
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 reliable heat-sealability and peelability across a wide temperature range, maintains optical clarity, and exhibits excellent winding behavior, even at elevated temperatures, ensuring effective packaging and reworkability without tearing or residue, thus addressing the limitations of prior art.
Implementation Method 1
The heat sealing of transparent meal trays made of APET or RPET takes place at sealing temperatures generally between 110 and 150 °C
Implementation Method 2
the packaging – even after storage in the refrigerator or freezer – is required to ensure that the sealed film can be easily peeled from the tray with noticeable force, without tearing
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to a transparent peelable polyester film comprising a biaxially oriented polyester film (B) having a first and a second surface, a further layer (C) applied to the first surface of the base layer (B), and a heat-sealable and peelable top layer (A) applied to the second surface of the base layer (B), wherein the heat-sealable and peelable top layer (A) is an offline coating and consists of (a) 85-99 wt.% polyester and (b) 1-15 wt.%-% of other substances, wherein the polyester is composed of 25-95 mol% of units derived from at least one aromatic dicarboxylic acid and 5-75 mol% of units derived from at least one aliphatic dicarboxylic acid, the sum of the dicarboxylic acid-derived mol% being 100, and the polyester is composed of at least 10 mol% of units derived from linear or branched diols with more than 2 carbon atoms, the sum of the diol components being 100 mol%, and the layer (C) comprises cross-linked acrylate and/or methacrylate-based copolymers. The invention further relates to a manufacturing process for this peelable polyester film and its use as a sealing film for APET and/or RPET meal trays.