Cyclocarbonate Polyurethane Adhesive for Food Packaging
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Solution Overview
Problem
Polyurethane-based adhesives used in flexible packaging often contain residual aromatic diisocyanates, leading to toxicity issues and instability, particularly during high-temperature sterilization processes, resulting in degradation of the adhesive joint and unsuitability for food packaging.
Innovation Solution
A two-component adhesive composition comprising cyclocarbonate-terminated polyurethane prepolymer and a diamine/polyamine mixture, with a specific molar ratio of primary amine functions to cyclocarbonate functions, which is free from residual polyisocyanates and exhibits improved thermal resistance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If NCO terminated polyurethane adhesives are used to achieve good adhesion properties, then adhesion performance is improved, but residual aromatic diisocyanate content increases leading to toxicity and stability problems
Solution Approach 1:
The harmful NCO groups are extracted and transformed through reaction with cyclocarbonate compounds. The patent converts the toxic isocyanate functionality into non-toxic cyclocarbonate-terminated polyurethane, eliminating residual diisocyanate while preserving adhesion properties through the resulting adhesive composition.
Solution Approach 2:
The chemical structure and properties of the polyurethane are changed by modifying the terminal groups from NCO to cyclocarbonate. This parameter change transforms the toxic, reactive NCO groups into stable, non-toxic cyclocarbonate groups, fundamentally altering the safety and stability parameters while maintaining adhesive performance.
2Object-affected harmful factors
If polyurethane compositions with low MDI content are used to reduce toxicity, then residual diisocyanate content is reduced, but viscosity increases and stability over time deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the polyurethane by introducing cyclocarbonate terminal groups, which fundamentally alter the molecular weight distribution and intermolecular interactions. This parameter change resolves the viscosity-stability issue by creating a molecular structure that maintains flow properties while improving temporal stability.
3Ease of manufacture
If conventional adhesives are used for multilayer packaging, then lamination process is simple, but thermal resistance during sterilization is insufficient leading to adhesive joint degradation
Solution Approach 1:
The patent creates a composite adhesive system by combining cyclocarbonate-terminated polyurethane with diamine/polyamine hardeners. This composite material approach provides both the simplicity of a two-component mixing process and superior thermal resistance, as the crosslinked network structure formed upon hardening delivers excellent sterilization resistance while maintaining ease of manufacture.
4Strength
If aromatic diisocyanate-based polyurethanes are used to achieve good adhesion, then bonding strength is improved, but chemical resistance and food safety are compromised
Solution Approach 1:
The harmful aromatic diisocyanate component is extracted and replaced with aliphatic or aromatic diisocyanates used only as intermediates that are fully consumed in the synthesis. The final adhesive contains no residual aromatic diisocyanate, eliminating toxicity while maintaining bonding strength through the cyclocarbonate-terminated polyurethane structure.
Solution Approach 2:
The chemical composition parameters are changed by eliminating aromatic diisocyanate residues and introducing cyclocarbonate terminal groups. This parameter change improves food safety and chemical resistance while preserving bonding strength, as the cyclocarbonate groups provide reactive functionality for crosslinking without the toxicological concerns of aromatic diisocyanates.
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 adhesive composition provides enhanced thermal resistance and stability, ensuring the multilayer structure's integrity during sterilization, making it suitable for food packaging without toxicity risks.
Implementation Method 1
preparing an NCO-terminated polyurethane prepolymer by a polyaddition reaction: i) of at least one polyisocyanate chosen from diisocyanates and triisocyanates, ii) with at least one polyol chosen from polyether polyols and polyester polyols
Implementation Method 2
The adhesive composition consists of composition A comprising at least one cyclocarbonate-terminated polyurethane prepolymer and composition B comprising at least one diamine and at least one polyamine
Data Source
AI summary
The invention relates to an adhesive dual-component composition comprising a composition A based on a polyurethane prepolymer with cyclocarbonate terminations and a composition B based on a mixture comprising at least one diamine B1 comprising only two primary amine groups of the -CH2-NH2 type and at least one polyamine B2 comprising at least three primary amine groups of the -CH2-NH2 type. The invention also relates to a multilayer structure produced from the adhesive composition according to the invention and to the method for the production thereof.