EBA Copolymer Adhesion of Foil to Polyolefins
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Solution Overview
Problem
The adhesion of low-density polyethylene (LDPE) to aluminum foil in multilayer structures deteriorates over time due to secondary crystallization and shrinkage, leading to reduced peel strength, and existing solutions like chemical primers are costly and environmentally concerning.
Innovation Solution
A multilayer structure comprising a layer of ethylene/butyl acrylate copolymer between the foil and a thermoplastic polyolefin composition enhances adhesion, eliminating the need for primers and maintaining bond strength over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If LDPE is used for extrusion lamination to aluminum foil, then initial adhesion is achieved through oxidation at high temperatures, but adhesion strength deteriorates over time due to secondary crystallization and shrinkage
Solution Approach 1:
The patent changes the chemical composition parameter of the adhesive layer from pure LDPE to an EBA copolymer with specific butyl acrylate content (20-40 mol%). This compositional parameter change fundamentally alters the material's crystallization behavior and adhesion mechanism, preventing the secondary crystallization-induced shrinkage that causes adhesion deterioration over time in pure LDPE systems
Solution Approach 2:
The patent creates a composite adhesive system by formulating an ethylene/butyl acrylate copolymer that combines the benefits of ethylene (compatibility with polyolefin substrates) and butyl acrylate (adhesion to aluminum foil). This composite polymer structure provides both initial adhesion and long-term durability by eliminating the harmful secondary crystallization phenomenon while maintaining bonding capability
2Strength
If chemical primers are used to promote adhesion to non-polar substrates, then adhesion is improved, but costs increase and environmental concerns arise from solvent-based systems
Solution Approach 1:
The patent extracts and eliminates the need for separate chemical primer layers by incorporating all necessary adhesion-promoting functionality directly into the EBA copolymer adhesive layer. The copolymer itself provides both polyolefin substrate compatibility and aluminum foil adhesion capability, removing the complexity of multi-layer primer systems and their associated solvent-based environmental issues
Solution Approach 2:
The EBA copolymer adhesive layer performs multiple functions simultaneously: it adheres to the non-polar polyolefin substrate through its ethylene component, bonds to the aluminum foil through its butyl acrylate component, and prevents secondary crystallization. This multi-functional adhesive layer replaces what would traditionally require separate primer layers and topcoat adhesives, simplifying the overall system
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 use of ethylene/butyl acrylate copolymer as an adhesive layer significantly improves and maintains the adhesion of foil to thermoplastic compositions, providing a durable and cost-effective solution for packaging applications.
Implementation Method 1
The invention relates to adhesion of foil to thermoplastic compositions comprising ethylene/butyl acrylate copolymer
Implementation Method 2
One explanation is that the aging may be associated with secondary crystallinity of the LDPE. During the lamination process, the LDPE is quenched very quickly and little primary crystallization can occur. Over time, small 'secondary' crystals may form. As PE crystallizes, it shrinks. Shrinkage can put a stress on bonds and reduce peel strength.
Data Source
AI summary
Disclosed is a multilayer structure, which comprises or is produced from a foil laminated to thermoplastic compositions using ethylene/butyl acrylate copolymer compositions as a tie layer. The multilayer structures can be useful as packaging films and industrial films. Also disclosed is a lamination process for producing the structure. Further disclosed are packages comprising the structures.