Polyester Sealant Film Composition for Sealing Without Curling
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Solution Overview
Problem
Conventional polyester sealants face issues such as adsorption of organic compounds, low heat sealing strength in low temperature regions, curling, and poor foldability, which affect their suitability for packaging applications.
Innovation Solution
A polyester sealant film with specific layer compositions and properties, including ethylene terephthalate as a main component, controlled diol monomer content, and reversible heat capacity differences, ensuring high heat sealing strength, resistance to curling, and excellent foldability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyolefin resin sealant layer is used to achieve high sealing strength, then heat sealing strength is improved, but the sealant adsorbs organic compounds such as fat or oil, changing the aroma or taste of content
Solution Approach 1:
The invention changes the chemical composition parameters of the sealant by using polyester resin instead of polyolefin resin, specifically controlling the diol component content (30-50 mol%) to achieve both high heat sealing strength and low adsorption of organic compounds
Solution Approach 2:
The invention uses a composite polyester resin system combining specific diol components (ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol) with terephthalic acid to create a material that exhibits both high sealing strength and resistance to organic compound adsorption
2Object-generated harmful factors
If an acrylonitrile resin sealant is used to reduce adsorption of organic compounds, then adsorption resistance is improved, but heat sealing strength becomes low in low temperature region (150°C or lower)
Solution Approach 1:
The invention changes the chemical composition by using polyester resin with controlled diol content (30-50 mol%) which provides both low organic compound adsorption and high heat sealing strength at low temperatures, replacing acrylonitrile resin
Solution Approach 2:
The invention optimizes the local chemical structure by selecting specific diol components and their ratios to create regions within the polymer chain that provide both adsorption resistance and low-temperature sealing capability
3Object-generated harmful factors
If a polyester sealant containing 2,6-naphthalene dicarboxylic acid and 1,3-propanediol is used to achieve non-adsorptivity, then adsorption resistance is improved, but the sealant melts and forms holes upon heat sealing due to low heat resistance
Solution Approach 1:
The invention changes the chemical composition by using terephthalic acid instead of 2,6-naphthalene dicarboxylic acid, and controlling diol content (30-50 mol%) to achieve both adsorption resistance and high heat resistance that prevents melting and hole formation
Solution Approach 2:
The invention extracts and removes the problematic 2,6-naphthalene dicarboxylic acid component from the polyester structure while retaining the beneficial low-adsorption properties through alternative chemical composition
4Strength
If a polyester sealant with laminated layers of greatly different compositions is used to achieve high heat sealing performance, then heat sealing strength is improved, but the sealant curls towards the heat sealing layer due to differential shrinkage
Solution Approach 1:
The invention applies local quality by using the same polyester base resin in both layers but varying only the diol component content (heat sealing layer: 30-50 mol%, heat resistant layer: 9-20 mol%) to achieve both high sealing strength and minimal curling through controlled differential shrinkage
Solution Approach 2:
The invention changes the compositional parameters by controlling the diol content difference between layers (20-35 mol%) to optimize both heat sealing performance and dimensional stability, preventing excessive curling
5Strength
If a polyester sealant with high heat sealing performance is used, then heat sealing strength is improved, but foldability becomes poor
Solution Approach 1:
The invention changes the chemical composition parameters by using polyester resin with controlled diol content (30-50 mol% in heat sealing layer) that provides both high heat sealing strength and good foldability through optimized molecular structure
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 solution provides a polyester sealant with enhanced heat sealing strength, resistance to curling, and improved foldability, making it suitable for packaging applications without holes or curling, and reducing adsorption of organic compounds.
Implementation Method 1
heat sealing strength, wherein the polyester sealant film satisfies following requirements (1) to (6): (1) a heat sealing strength of the heat sealing layer being heat-sealed to another heat sealing layer at 140°C and 0.2 MPa for 2 seconds is 8 N/15 mm or more and 20 N/15 mm or less
Implementation Method 2
the heat sealing layer has a difference in reversible heat capacity (ΔCp) between a glass transition temperature and 140°C of 0.5 J/g/K or more and 1.1 J/g/K or less when measured with a temperature modulated DSC
Data Source
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AI summary
The present invention provides a polyester sealant film that is less prone to adsorb a component of its content, having not only high heat strength in a low temperature region but also no hole thereon upon heat sealing. Furthermore, the polyester sealant film is little curl attributed to laminating and is excellent in foldability. The present invention also provides a laminate comprising at least one layer of the polyester sealant and provide a packaging bag comprising the laminate. The polyester sealant film having at least one of a heat sealing layer and a heat resistant layer, wherein each layer consists of a polyester component which comprises ethylene terephthalate as a main component, wherein the polyester sealant film satisfies following requirements (1) to (6): (1) a heat sealing strength of the heat sealing layers being heat-sealed to another heat sealing layer at 140°C and 0.2 MPa for 2 seconds is 8 N/15 mm or more and 20 N/15 mm or less; (2) the heat sealing layer has a difference in reversible heat capacity (ΔCp) between a glass transition temperature and 140°C of 0.5 J/g/K or more and 1.1 J/g/K or less when measured with a temperature modulated DSC; (3) the heat resistant layer has a ΔCp of 0.1 J/g/K or more and less than 0.6 J/g/K when measured with the temperature modulated DSC; (4) the film has a fold holding angle of 20 degrees or more and 60 degrees or less; (5) the film has a smaller curvature radius of 50 mm or more and 300 mm or less in a longitudinal direction or a widthwise direction; and (6) the film has a heat shrinkage ratio of -5% or more and 5% or less in both a longitudinal direction and a widthwise direction after immersed in hot water of 80°C for 10 seconds.