Polyurethane Adhesive Heat Resistance via NCO Conversion
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Solution Overview
Problem
Polyurethane-based compositions used in flexible packaging face challenges with high residual aromatic diisocyanate content leading to toxicity issues and poor heat resistance, particularly during sterilization, where multilayer structures show signs of degradation such as unevenness and un-crosslinking.
Innovation Solution
A polyurethane-based adhesive composition with specific end functions and a reaction process that minimizes residual diisocyanate content and enhances heat resistance, comprising a polyurethane with end functions T and an amine, synthesized through a polyaddition reaction with controlled NCO/OH mole ratios, resulting in improved reactivity at moderate temperatures and enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyurethane-based compositions bearing NCO end groups are used for adhesive applications, then good adhesion properties are achieved, but residual aromatic diisocyanate content becomes high leading to toxicity problems
Solution Approach 1:
The patent extracts and removes the harmful NCO end groups from the polyurethane structure through reaction with compounds containing active hydrogen (alcohols, carboxylic acids, water). This eliminates the source of residual aromatic diisocyanate while preserving the adhesive properties of the polyurethane backbone structure.
Solution Approach 2:
The patent converts the potentially harmful NCO end groups into beneficial functional groups. By reacting NCO groups with compounds containing active hydrogen, the harmful isocyanate residues are transformed into stable urethane, urea, and carbamate linkages that improve both safety and performance.
2Object-affected harmful factors
If residual diisocyanate content is reduced to less than 0.1% by weight, then toxicity requirements are met, but the composition becomes highly viscous at room temperature and exhibits stability problems
Solution Approach 1:
The patent changes the chemical composition parameters by introducing specific compounds containing active hydrogen (alcohols with 1-12 carbon atoms, carboxylic acids with 1-12 carbon atoms) in controlled amounts (0.1-10% by weight). This modifies the molecular structure and intermolecular forces, reducing viscosity while maintaining stability.
Solution Approach 2:
The patent creates a composite adhesive system combining polyurethane with multiple components: compounds containing active hydrogen, optional solvents, and optional additives. This multi-component composite approach allows tuning of viscosity and stability properties while keeping residual diisocyanate below 0.1%.
3Strength
If conventional polyurethane adhesives are used for multilayer packaging, then lamination is achieved, but heat resistance during sterilization is poor causing degradation
Solution Approach 1:
The patent converts the thermally unstable NCO end groups into thermally stable functional groups through reaction with compounds containing active hydrogen. The resulting urethane, urea, and carbamate linkages maintain bond strength during sterilization temperatures while the eliminated NCO groups prevent thermal degradation.
Solution Approach 2:
The patent changes the thermal stability parameters by modifying the chemical structure through controlled reactions. The stoichiometric balance and selection of compounds containing active hydrogen are optimized to achieve both adequate bonding strength at lamination temperature and sufficient heat resistance at sterilization temperature.
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 composition achieves better heat resistance and stability during sterilization, reducing the risk of degradation and ensuring the integrity of flexible packaging materials.
Implementation Method 1
synthesized through a polyaddition reaction with controlled NCO/OH mole ratios
Data Source
AI summary
The invention relates to a composition comprising: —a composition A containing at least one polyurethane comprising at least two terminal functions T of formula (I): and —a composition B comprising at least one amine. Also disclosed is the use of said composition.