Multilayer Thermoshrinkable Film Orientation Stability
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Solution Overview
Problem
Multilayer thermoshrinkable films face issues such as film tearing and instability during the orientation process due to high temperature requirements, poor compatibility between polyethylene-based and polypropylene-based layers leading to delamination, and increased polymer extractability with certain copolymer compositions, which restricts their application in the food sector.
Innovation Solution
A multilayer film structure where one layer comprises a copolymer of propylene with hexene-1 and another layer comprises a copolymer of ethylene with α-olefins, optimized with specific molecular weight, density, and crystallinity, using stereospecific Ziegler-Natta catalysts to enhance mechanical, optical, and sealability properties, allowing for easier orientation at lower temperatures and improved food packaging compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the orientation process is carried out at high temperature to achieve film orientation, then the film can be oriented, but the film may tear or become unstable
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer layers, specifically using LLDPE with controlled comonomer content (0.5-20 mol%) and incorporating compatible polypropylene-based polymers with specific melt flow rates. This compositional parameter change allows the film to be oriented at lower temperatures (reducing thermal stress and instability) while maintaining orientability through controlled crystallinity and melt behavior.
Solution Approach 2:
The patent creates a composite multilayer structure combining polyethylene-based layers (LLDPE) with polypropylene-based layers (homopolymer or copolymer). The careful selection of compatible polymers with matched rheological properties enables the composite structure to achieve both orientability and stability during the orientation process, preventing tearing and bubble instability while maintaining structural integrity.
2Ease of operation
If PP or EPC is used in outer layers to improve sealability, then sealability is improved, but the working temperature range is restricted and shifted towards high temperatures
Solution Approach 1:
The patent modifies the compositional parameters by using LLDPE as the base material with controlled comonomer content rather than relying on PP or EPC. This parameter change enables sealability at lower temperatures while expanding the working temperature range, as LLDPE exhibits better low-temperature sealability and maintains stability across a broader temperature spectrum compared to PP-based solutions.
3Temperature
If PBC is used in outer layers to reduce sealability temperature, then sealability temperature is reduced, but polymer extractability increases to unacceptable levels
Solution Approach 1:
The patent changes the polymer composition parameters by using LLDPE with controlled comonomer content (0.5-20 mol%) instead of PBC. This parameter change achieves low sealability temperature (improving ease of operation) while simultaneously controlling polymer extractability to acceptable levels, as LLDPE exhibits lower extractability compared to PBC containing large amounts of butene, thus resolving the contradiction between sealability and food sector applicability.
4Manufacturing precision
If polyethylene-based layers are linked with polypropylene-based layers to improve film properties, then film properties are improved, but delamination occurs due to poor compatibility
Solution Approach 1:
The patent changes the compositional parameters by using LLDPE with controlled comonomer content as the primary material and incorporating polypropylene-based polymers with specific characteristics (melt flow rate 1-10 g/10min, controlled comonomer content). This parameter matching creates compositional compatibility between layers, ensuring proper adhesion and preventing delamination while maintaining improved film properties.
Data Source
AI summary
A multilayer film in which at least one layer (A) comprises a copolymer (A1) of propylene with hexene-1 containing from 4 to 10% by weight of hexene-1 and having Melt Flow Rate from 1 to 10 g/10 min.; and at least one layer (B) comprises a copolymer (B1) of ethylene containing up to 20 mol % of CH2=CHR a-olefins and having a density from 0.88 to 0.945 g/cm3.