Multilayered Aliphatic Polyester Film Heat Sealing
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Solution Overview
Problem
Conventional heat-sealing plastic films, such as polyvinyl chloride, polyethylene, and polypropylene, lack satisfactory performance characteristics like heat adhesiveness, heat resistance, and dimensional stability, while biodegradable aliphatic polyester films like polylactic acid-based films suffer from poor heat adhesiveness and flexibility due to high crystallinity, and existing multilayered films have issues with heat shrinkage and transparency under hot bath treatments.
Innovation Solution
A multilayered aliphatic polyester film is developed with a first resin layer containing 50-100% L-lactic acid and a second resin layer with 5-20% D-lactic acid, achieving improved heat adhesiveness, heat resistance, transparency, impact resistance, and dimensional stability through specific composition and processing methods like co-extrusion and heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If biodegradable aliphatic polyester films like polylactic acid-based films are employed, then environmental friendliness is improved, but heat adhesiveness and flexibility deteriorate due to high crystallinity
Solution Approach 1:
The patent changes the stereochemical parameters of the polylactic acid polymer by controlling the D/L ratio to create different crystallinity regions. The first resin layer uses high L-lactic acid content (90-100%) for high crystallinity and heat resistance, while the second resin layer uses balanced D/L content (40-60% D-lactic acid) for low crystallinity and good heat adhesiveness, thus resolving the contradiction between environmental friendliness and heat adhesiveness
Solution Approach 2:
The patent creates a composite multilayered film structure combining two different polylactic acid-based resins with distinct stereochemical compositions. This composite structure allows the high-crystallinity layer to provide heat resistance while the low-crystallinity layer provides heat adhesiveness, solving the contradiction between these opposing properties in a single biodegradable material system
2Strength
If multilayered film with aliphatic polyester resin having Tg of 0°C or lower is employed, then heat adhesiveness is improved, but heat resistance deteriorates resulting in high heat shrinkage
Solution Approach 1:
The patent applies local quality by assigning different stereochemical compositions to different layers: the first resin layer (non-adhesive layer) uses high L-lactic acid content for high crystallinity and heat resistance, while the second resin layer (adhesive layer) uses balanced D/L content for low crystallinity and heat adhesiveness. This spatial differentiation of material properties resolves the contradiction between heat adhesiveness and heat resistance
3Strength
If amorphous lactic acid-based resin layer is employed as heat-sealant layer, then heat adhesiveness is improved, but transparency deteriorates during hot bath treatment
Solution Approach 1:
The patent optimizes the stereochemical parameters by controlling the D-lactic acid content in the adhesive layer to 40-60%, which provides sufficient amorphous content for heat adhesiveness while maintaining adequate crystalline regions to prevent clouding during hot bath treatment, thus resolving the contradiction between heat adhesiveness and transparency
4Strength
If conventional heat-sealing plastic films like polyethylene are employed, then heat adhesiveness is improved, but dimensional stability and mechanical properties deteriorate
Solution Approach 1:
The patent creates a composite multilayered structure where the high-crystallinity first resin layer provides dimensional stability and mechanical strength, while the low-crystallinity second resin layer provides heat adhesiveness. This composite approach allows the film to achieve both good heat sealing properties and dimensional stability without using conventional non-biodegradable materials
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 exhibits enhanced heat adhesive strength, reduced haze, and improved impact and perforation resistance, allowing easy peeling and maintaining integrity after heat sealing, making it suitable for packaging applications.
Implementation Method 1
such films have poor heat adhesiveness and flexibility due to their high crystallinity
Implementation Method 2
after being subjected to hot bath treatment at 85° C. for 30 minutes
Data Source
AI summary
A multilayered aliphatic polyester film of the present invention comprising a first resin layer and a second resin layer laminated on one or both sides of the first resin layer, the first resin layer containing a polylactic-based polymer comprising L-lactic acid in an amount ranging from 50 to 100% by weight, and the second resin layer containing a polylactic-based polymer comprising D-lactic acid in an amount ranging from 5 to 20% by weight, can be easily peeled off by pulling with hands, and has improved heat adhesiveness, heat resistance, transparency, impact resistance, perforation resistance and dimensional stability. Accordingly, it is useful for packaging materials, especially as a disposable film lid for plastic containers.