Stretch-Oriented PET Film for Heat-Resistant Oven Board
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Solution Overview
Problem
Existing methods for producing polymer-coated oven boards face challenges in achieving sufficient heat resistance and gas barrier properties while avoiding cracking and reducing polymer material thickness, as they require thick PET layers for bonding with PA layers, which are not heat-resistant and prone to cracking.
Innovation Solution
A method involving extrusion lamination of a stretch-oriented PET film with a premade solid film and an adhesive PA layer, where the PA layer acts as a bonding medium, allowing for a thinner PET coating and improved crystallization for enhanced strength and barrier properties, and optionally incorporating PETG for better moldability and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick PET coating layer is used to ensure heat resistance and bonding strength, then the heat resistance and bonding are improved, but the polymer material usage increases and the layer becomes prone to cracking at bends and corners
Solution Approach 1:
The patent changes the physical state parameter of the PET coating from amorphous (extruded) to crystalline (laminated on pre-stretched film). This crystallization transforms the material properties, enabling thinner layers to achieve the same or better heat resistance and bonding strength without cracking, thus reducing polymer material usage by up to 50%.
Solution Approach 2:
The PET film is pre-stretched and crystallized before lamination to the board base. This preliminary action of stretching and crystallizing the film beforehand allows the final coating to be thinner while maintaining structural integrity and heat resistance, avoiding the need for thick amorphous extruded layers.
2Ease of manufacture
If an amorphous extruded PET coating layer is used, then the manufacturing process is simpler, but the gas barrier properties are insufficient and the layer does not crystallize
Solution Approach 1:
The manufacturing process is segmented into two independent stages: (1) production of pre-stretched crystalline PET film, and (2) lamination of this pre-prepared film to the board base with PA adhesive. This segmentation allows the film to be crystallized and optimized for gas barrier properties before application, while keeping the lamination process simple and efficient.
3Loss of substance
If the PET coating layer is made thinner to reduce material usage, then polymer material consumption decreases, but the bonding strength and heat resistance may be compromised
Solution Approach 1:
The patent creates a composite structure where a thin crystalline PET film is laminated onto a board base with a PA adhesive layer. The combination of pre-stretched crystalline PET (providing heat resistance and gas barrier) with PA adhesive (providing strong bonding) enables thin coating layers to achieve sufficient bonding strength and heat resistance without compromising performance.
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
This approach reduces polymer material usage by up to 50% and prevents cracking, providing a heat-resistant, gas-tight, and oxygen-impermeable coating suitable for dual-ovenable food packaging with improved mechanical strength and barrier properties.
Implementation Method 1
an adhesive layer comprising polyamide (PA) is extruded between the heat-resisting film and the board base
Implementation Method 2
Stretching brings about crystallization and thereby increased strength and improved gas barrier properties
Data Source
Figure 1~6
AI summary
The invention covers a method of producing a heat- resistant polymer-coated oven board, the resulting oven board, a food tray and a food package, which comprise such board and withstand heating in a range or microwave oven. According to the invention the coated oven board (1 ) is made by adhering a premade heat-resisting film (4) comprising polyethylene terephthalate (PET) or its derivate, such as glycol-modified PET known as PETG, to a board base (2) by extrusion lamination, in which an adhesive layer (3) comprising polyamide (PA) is extruded between the heat-resisting film and the board base. To improve the strength and barrier properties, the film (4) may be an extruded multilayer film and/or the film may be stretch-orientated to bring about crystallization in PET.