(Co)polyester Heat Seal Layer for Resealable Food Containers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing heat seal films for containers struggle to provide a strong initial bond strength, resealability, and antifog properties, especially in food packaging applications where transparency and moisture resistance are crucial.
Innovation Solution
A composition comprising a (co)polyester resin with specific thermal properties and an antifog agent, which forms a heat seal layer that is transparent, has low haze, and maintains resealability, is developed. This composition has a higher heat of fusion and lower glass transition temperature than the (co)polyester resin alone, enhancing its antifog and resealable properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional heat seal films are used, then initial bond strength is achieved, but resealability and antifog properties are compromised
Solution Approach 1:
The patent employs a composite material system consisting of a polyester base layer and a heat seal layer with specific composition (amorphous polyester, crystalline polyester, and plasticizer in controlled ratios). This composite structure enables the film to simultaneously achieve strong initial bonding through the heat seal layer's thermal properties while maintaining resealability and antifog properties through the coordinated interaction of composite components.
Solution Approach 2:
The patent optimizes specific parameter ranges including the heat of fusion (0.1-8 J/g), glass transition temperature (50-100°C), and compositional ratios of amorphous to crystalline polyester. By precisely controlling these parameters, the film achieves a balance between initial bond strength and resealability, allowing the material to transition between rigid and flexible states for different functional requirements.
2Reliability
If heat seal films with strong bonding are used, then seal integrity is improved, but transparency and antifog performance deteriorate
Solution Approach 1:
The patent applies local quality by differentiating the properties of different layers: the base layer provides structural integrity and transparency, while the heat seal layer (3-20 μm thick) provides localized bonding functionality. The heat seal layer's composition is specifically tailored to provide seal integrity without compromising the overall transparency of the film structure.
Solution Approach 2:
The patent controls the thickness of the heat seal layer within 3-20 μm and optimizes the plasticizer content (0.1-5 parts by weight per 100 parts polyester) to maintain transparency while achieving adequate seal integrity. These parameter optimizations ensure that the bonding function does not compromise the optical properties required for antifog performance and product visibility.
3Object-affected harmful factors
If the heat of fusion of the resin is increased, then antifog properties are enhanced, but glass transition temperature increases reducing flexibility
Solution Approach 1:
The patent establishes an optimal balance by limiting the heat of fusion to 0.1-8 J/g and the glass transition temperature to 50-100°C. This parameter optimization ensures that the resin provides sufficient antifog properties through appropriate crystallinity while maintaining flexibility through controlled glass transition behavior, preventing the material from becoming too rigid.
Solution Approach 2:
The patent uses different polyester components with complementary properties: amorphous polyester contributes to flexibility and low glass transition temperature, while crystalline polyester provides antifog properties through controlled crystallinity and heat of fusion. The plasticizer further modifies local properties to enhance flexibility without significantly affecting the antifog mechanism.
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 achieves a strong initial bond strength, maintains resealability, and effectively prevents fogging, ensuring the contents of the container remain well-preserved and visible, meeting the requirements for food packaging.
Implementation Method 1
heat seal technique (e.g., melt-bead sealing, thermal sealing, impulse sealing, ultrasonic sealing, hot air, hot wire, infrared radiation)
Implementation Method 2
formation of a fusion bond to a second portion of a film surface
Implementation Method 3
the film avoids fogging. Fogging tends to limit the visibility of the contents of the container to a consumer due to moisture condensating on the inside of the film
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
A composition comprises a (co)polyester resin having a heat of fusion of 0.1 to 8 J/g and a glass transition temperature between about 50°C and 100°C and an antifog agent, wherein the composition has a heat of fusion of greater than the heat of fusion of the (co)polyester resin and a glass transition temperature less than the glass transition temperature of the (co)polyester resin. The composition may be used as a heat seal layer as part of a laminate for a container, such as an amorphous polyester tray and, when used with a pressure sensitive adhesive layer, may have the ability to reseal the container. The composition may also be used as a heat seal layer of a laminate for use used as a bag or pouch. The composition may be compliant for food contact.