Polyolefin Tie-Layer Blend for Adhesion and Processability
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Solution Overview
Problem
Anhydride-grafted polyolefins have limitations in adhesion promotion due to degradation at high anhydride levels and processability issues with high co-monomer content ethylene polar terpolymers, leading to poor adhesion and processing problems in bonding polar polymers to polyolefin substrates in coextrusion and oriented film applications.
Innovation Solution
A laminate film structure incorporating a blend of ethylene-propylene copolymer and ethylene polar terpolymer as a tie-layer, which promotes effective adhesion between polypropylene substrates and polar materials like EVOH, maintaining adhesion properties while improving processability in coextrusion and biaxial orientation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If anhydride-grafted polyolefins are used as tie-layers to bond polar polymers to polyolefin substrates, then adhesion between polar and non-polar layers is improved, but the polyolefin degrades at high anhydride levels limiting adhesion performance
Solution Approach 1:
The patent changes the chemical composition parameters of the tie-layer by using ethylene polar terpolymer with controlled co-monomer content (2-20 mol%) instead of anhydride-grafted polyolefin. This parameter change allows achieving adhesion promotion without the degradation issues associated with high anhydride levels, as the terpolymer structure inherently provides polarity and compatibility without requiring grafting reactions that can degrade the base polyolefin.
Solution Approach 2:
The patent employs a composite tie-layer material consisting of ethylene polar terpolymer blended with polyethylene or polypropylene. This composite approach combines the adhesion-promoting properties of the polar terpolymer with the mechanical strength and processability of the non-polar polyolefin base, achieving both strong adhesion and material stability without degradation.
2Strength
If high co-monomer content ethylene polar terpolymer is used to promote adhesion, then bonding between polar polymers and polyolefin substrates is improved, but processability deteriorates due to processing problems
Solution Approach 1:
The patent optimizes the co-monomer content parameter within a specific range (2-20 mol%) to balance adhesion promotion and processability. This controlled parameter change ensures sufficient polarity for adhesion while maintaining melt flow and processing characteristics adequate for coextrusion and orientation processes, avoiding the processing problems associated with high co-monomer content.
Solution Approach 2:
The patent applies local quality by using a blend composition where the ethylene polar terpolymer (providing adhesion) is combined with polyethylene or polypropylene (providing processability). This local composition strategy ensures that different regions of the tie-layer material provide different functions: adhesion promotion where needed and processability where required.
3Ease of manufacture
If low co-monomer content ethylene polar terpolymer is used, then processability is improved, but adhesion promotion is insufficient
Solution Approach 1:
The patent identifies and applies an optimal parameter range for co-monomer content (2-20 mol%) that simultaneously provides adequate adhesion promotion and processability. This parameter optimization resolves the trade-off by finding the sweet spot where the polar character is sufficient for bonding while the polymer chain structure remains processable.
Solution Approach 2:
The patent uses composite blending of ethylene polar terpolymer with polyethylene or polypropylene to achieve synergistic effects. The terpolymer component (even at lower concentrations) provides adhesion promotion, while the polyolefin base maintains processability, creating a composite material that overcomes the limitations of using either component alone.
4Strength
If anhydride-grafted polyolefins are used as tie-layers, then adhesion between polar and non-polar layers is improved, but manufacturing complexity increases due to degradation issues and limited formulations
Solution Approach 1:
The patent simplifies the formulation by changing from anhydride-grafted polyolefin to ethylene polar terpolymer with controlled co-monomer content. This parameter change eliminates the need for complex grafting reactions and reduces formulation complexity while maintaining adhesion performance and avoiding degradation issues.
Solution Approach 2:
The patent adopts a simpler, more straightforward polymer structure (ethylene polar terpolymer) that can be directly processed without requiring additional chemical modifications or complex formulation strategies. This approach uses readily available materials that can be processed through standard coextrusion equipment without specialized conditions.
Data Source
AI summary
A laminate film including a first polyolefin layer comprising of a blend of 50-95% ethylene-propylene copolymer and 50-5% ethylene polar terpolymer with a polar polymer layer on one side of said first polyolefin resin-containing layer is disclosed. The laminate film could further have additional layers such as a second polyolefin resin-containing layer, a metal layer, or combinations thereof.