Multilayer Film Structures Using Triple Bubble Process
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Solution Overview
Problem
The manufacture of multilayer films comprising mono- or bi-axially oriented polytrimethylene terephthalate or polytrimethylene furanoate is challenging due to thermal shrinkage issues at processing temperatures, leading to inhomogeneous thickness and reduced mechanical and barrier properties, and existing solutions like adhesive lamination pose economic and environmental concerns.
Innovation Solution
A triple bubble (3B) process is employed to coextrude a multilayer film structure with a layer of mono- or bi-axially oriented polytrimethylene terephthalate or polytrimethylene furanoate, a tie layer, and a sealant layer, involving cooling, orientation, and relaxation under controlled heating to achieve stable and self-sustaining bubbles with improved stretchability and reduced rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If polytrimethylene terephthalate or polytrimethylene furanoate is used as a renewable polyester alternative to PET, then environmental sustainability is improved, but thermal shrinkage at processing temperatures causes inhomogeneous thickness and reduced mechanical properties
Solution Approach 1:
The patent modifies the polymer composition by blending polytrimethylene terephthalate or polytrimethylene furanoate with polyethylene terephthalate in specific ratios (e.g., 20-80 wt% renewable polyester with 80-20 wt% PET) to adjust thermal properties. This parameter change allows the material to maintain dimensional stability at processing temperatures while retaining renewable content benefits, thereby resolving the contradiction between environmental sustainability and manufacturing precision.
Solution Approach 2:
The patent creates composite multilayer film structures combining renewable polyester layers with PET layers and sealant layers. The composite structure leverages the thermal stability of PET to compensate for the shrinkage tendency of renewable polyesters during processing, achieving both environmental benefits and consistent thickness uniformity across the film.
2Ease of manufacture
If adhesive lamination is used to manufacture multilayer films with renewable polyester, then layer bonding is achieved, but economic cost and environmental concerns increase
Solution Approach 1:
The patent converts the naturally occurring surface properties of the renewable polyester and PET layers into beneficial bonding interfaces. By selecting compatible polymer combinations and optimizing processing temperatures, the patent enables direct thermal bonding between layers without requiring additional adhesive materials, thereby eliminating the harmful effects of adhesive lamination while maintaining ease of manufacture.
Solution Approach 2:
The patent uses a tie layer composed of compatible polymers (such as polyethylene terephthalate or polyethylene) as an intermediary between the renewable polyester layer and the sealant layer. This intermediary layer facilitates bonding between layers with different surface properties, achieving effective layer bonding without requiring harmful adhesive materials.
3Productivity
If conventional calendering or lamination processes are used to process renewable polyester, then multilayer film production is achieved, but thermal shrinkage leads to reduced mechanical and barrier properties
Solution Approach 1:
The patent incorporates the renewable polyester into a multilayer structure during the extrusion process itself, rather than attempting to laminate pre-formed sheets. This preliminary action of co-extruding multiple layers in a single operation allows for controlled thickness and proper layer adhesion before thermal shrinkage can occur, maintaining both productivity and mechanical properties.
Solution Approach 2:
The patent optimizes processing parameters including extrusion temperature, cooling rate, and draw ratio to minimize thermal shrinkage effects. By carefully controlling these parameters during the extrusion and orientation processes, the patent maintains the mechanical strength and barrier properties of the renewable polyester layers while achieving efficient multilayer film production.
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 process results in coextruded multilayer films with stable thickness, enhanced stretchability, and improved mechanical and barrier properties compared to conventional polyethylene terephthalate-based solutions, while avoiding the drawbacks of thermal shrinkage and adhesive lamination.
Implementation Method 1
mono- or bi-axially orienting at least one layer of the coextruded tubular multilayer film structure under heating in a second bubble; and relaxing the mono- or bi-axially oriented coextruded tubular multilayer film structure under heating in a third bubble
Implementation Method 2
cooling the coextruded tubular multilayer film structure in a first bubble
Data Source
Figure 1
AI summary
Disclosed is a multilayer structure such as coextruded multilayer structure, comprising at least one layer of a polymer composition, at least one tie layer, and at least one sealant layer. The polymer composition comprises polytrimethylene terephthalate and/or polytrimethylene furanoate, and the layer comprising the polymer composition is preferably mono- or bi-axially oriented. Also disclosed is a triple bubble (3B) process for producing the multilayer structure.