Epoxy-Polyester Adhesive Eliminates Bisphenol-A Contamination
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Solution Overview
Problem
Bisphenol-A-based epoxy resins and isocyanate-based materials in laminating adhesives pose safety concerns and can contaminate food, necessitating the development of alternatives that are free from these substances while maintaining effective adhesive properties.
Innovation Solution
A curable formulation comprising a blend of epoxy-terminated polyester, maleate (poly) ester, or diacrylate terminated oligomer with an aliphatic amine curing agent, which provides a solvent-free or low-solvent adhesive with a bond strength range of 1.5 to 5.0 N/15 mm and viscosity ≤6500 mPa*s at 50°C, suitable for food packaging applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If isocyanate-based materials are used in laminating adhesives, then adhesive performance is improved, but safety issues and food contamination risks arise
Solution Approach 1:
The patent removes isocyanate-based materials from the adhesive formulation entirely, extracting the harmful component while maintaining adhesive functionality through alternative chemistry (epoxy-terminated polyester with carboxylic acid or hydroxyl groups). This directly addresses the food safety concern by eliminating the source of harmful isocyanate residues that could migrate into food packaging.
Solution Approach 2:
The invention changes the chemical composition parameters of the adhesive system by substituting isocyanate crosslinking mechanisms with carboxylic acid or hydroxyl-based crosslinking. This parameter change eliminates the formation of potentially harmful aromatic amines while achieving comparable or superior adhesive performance through different chemical pathways.
2Strength
If bisphenol-A-based epoxy resins are used in laminating adhesives, then adhesive strength is achieved, but food contamination and safety concerns arise
Solution Approach 1:
The patent extracts and eliminates bisphenol-A from the epoxy resin structure, using alternative epoxy-terminated polyester formulations that achieve comparable adhesive strength without the harmful bisphenol-A component. This directly removes the food safety hazard while preserving the essential adhesive function.
Solution Approach 2:
The invention employs composite material strategies by combining epoxy-terminated polyester with carboxylic acid-terminated polyester or hydroxyl-containing polymers to create a multi-component system that achieves the desired adhesive performance without relying on bisphenol-A-based epoxy resins.
3Adaptability or versatility
If monomers and oligomers with atomic mass less than 1000 Daltons are used, then adhesive formulation flexibility is improved, but migration into food increases if not completely reacted
Solution Approach 1:
The patent changes the molecular weight parameters of the adhesive components by using epoxy-terminated polyester and carboxylic acid-terminated polyester with higher molecular weights that reduce migration potential. The formulation maintains flexibility through adjustable ratios of components while ensuring lower migration risk through careful selection of polymer chain lengths.
Solution Approach 2:
The invention converts the potential harm of low molecular weight migration into a benefit by using controlled polymerization to create oligomers that are large enough to minimize migration but small enough to maintain reactivity and adhesive performance. The carboxylic acid termination provides reactive end groups that ensure complete crosslinking, eliminating residual low molecular weight species.
4Strength
If isocyanate-based resins are used, then adhesive performance is improved, but primary aromatic amines are generated which can migrate into food
Solution Approach 1:
The patent extracts and eliminates the isocyanate component from the adhesive system, preventing the formation of primary aromatic amines through alternative crosslinking chemistry using carboxylic acid or hydroxyl groups. This directly removes the source of harmful amine generation while maintaining adhesive functionality.
Solution Approach 2:
The invention substitutes the isocyanate-based crosslinking mechanism with carboxylic acid or hydroxyl-based crosslinking chemistry. This mechanical/chemical substitution replaces the harmful isocyanate reaction pathway with a safer alternative that achieves comparable network formation without generating aromatic amines.
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 formulation achieves strong adhesive bonds and is free from potential food contaminants, ensuring safety and efficacy in food packaging applications while minimizing the risks associated with bisphenol-A and isocyanate-based materials.
Implementation Method 1
a curable formulation comprising a) a blend comprising i) an epoxy terminated polyester... and b) an aliphatic amine curing agent
Implementation Method 2
at least one of ii) a maleate (poly) ester having a structure... or iii) a diacrylate terminated oligomer or polymer
Data Source
AI summary
The instant invention provides a curable formulation suitable for laminating adhesive applications, and laminating adhesives made therefrom. The curable formulation suitable for laminating adhesive applications according to the present invention comprises a) a blend comprising i) an epoxy terminated polyester and at least one of ii) a maleate (poly) ester or iii) a diacrylate terminated oligomer or polymer and b) an aliphatic amine curing agent.