Cross-Linked Multilayer Film for Vacuum Skin Packaging
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Solution Overview
Problem
Current vacuum skin packaging films face challenges in achieving a balance of high formability, implosion resistance, easy openability, and drip retention, particularly when sealed onto polyester-based supports, and struggle with sealing characteristics and drip loss issues.
Innovation Solution
A cross-linked top film with a specific composition, including a sealant layer of (co)polyesters with controlled glass transition and melting point temperatures, combined with a tie layer and an abuse layer, which allows for excellent sealability on various materials and prevents drip loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional VSP films are used to ensure sealing on polyester supports, then seal strength is improved, but easy openability deteriorates
Solution Approach 1:
The sealing layer is divided into multiple functional segments: a first polymer component (polyester) provides strong adhesion to polyester supports for hermetic sealing, while a second polymer component (polyolefin or polyamide) provides controlled adhesion for easy opening. This segmentation allows each component to specialize in one function, resolving the contradiction between strong sealing and easy opening.
Solution Approach 2:
The sealing layer exhibits different adhesion properties at different interfaces: high adhesion to polyester supports (for sealing integrity) and controlled adhesion to the film body (for easy opening). This local differentiation of adhesive properties allows the seal to be strong where needed while remaining openable where required.
2Adaptability or versatility
If films are made highly formable to conform to product shape, then formability is improved, but implosion resistance deteriorates
Solution Approach 1:
The film uses a composite structure with multiple layers having different functional properties. The abuse layer contains high-strength polymers (polyolefins, polyamides, or styrene-based polymers) that provide implosion resistance, while the sealing layer contains polyester and polyolefin/polyamide components that provide formability. This composite approach allows simultaneous achievement of both formability and implosion resistance.
Solution Approach 2:
The patent addresses the formability-implosion resistance trade-off by adding a dimensional aspect through multi-layer construction. Rather than trying to optimize a single layer for both properties, the solution distributes functions across multiple layers, with each layer optimized for its specific function, thereby resolving the contradiction through structural dimensionality.
3Reliability
If seal strength is increased to maintain hermeticity, then package integrity is improved, but easy openability deteriorates
Solution Approach 1:
The sealing layer is segmented into two polymer components with different adhesion characteristics. The polyester component ensures strong bonding to polyester supports for hermetic sealing and package integrity, while the polyolefin or polyamide component provides controlled adhesion that allows easy opening. This segmentation enables the seal to be both strong and openable.
Solution Approach 2:
The patent changes the compositional parameters of the sealing layer by incorporating specific polymer types with different adhesion properties. By adjusting the polymer composition (polyester combined with polyolefin or polyamide), the seal achieves optimal balance between hermeticity (for integrity) and openability, resolving the contradiction through parameter optimization.
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 cross-linked film provides enhanced formability, implosion resistance, easy openability, and improved drip retention, ensuring effective sealing and product preservation, even after heat treatments.
Implementation Method 1
The films have to stand the heating and stretching conditions within the vacuum chamber of the packaging machine without undergoing excessive softening and perforations, they must be highly formable and have an excellent implosion resistance
Implementation Method 2
The adhesion of the top to the bottom is achieved through the draping of the heated top onto the entire surface of the bottom not covered by the product after removal of the vacuum from the dome
Implementation Method 3
The top flexible film is also referred to as 'skin-forming', 'skin' or 'upper' film... The upper heated film forms a tight skin around the product
Implementation Method 4
Vacuum skin packaging (VSP) is a process well known in the art using a thermoplastic packaging material to enclose a food product. The terms 'vacuum skin packaging' or 'VSP' as used herein indicate that the product is packaged under vacuum and the space containing the product is evacuated from gases
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to packaging films, more specifically to cross-linked packaging films useful in vacuum skin packaging applications characterized by versatile sealing properties, especially by unexpected versatile sealability on polyester and on different substrates, to a method of packaging by using said films and to packages obtained therewith. Said packages show high drip retention, easy openability and good performance in microwave applications.