Polyurethane Adhesive Composition for Flexible Packaging
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Solution Overview
Problem
Two-component polyurethane-based adhesive compositions used in flexible packaging face challenges due to high residual diisocyanate monomers, which are toxic and require additional processing steps to remove, limiting their suitability for metal materials and increasing environmental concerns.
Innovation Solution
A two-component polyurethane-based adhesive composition with a polyurethane prepolymer obtained from an asymmetric diisocyanate and a diol, combined with a triisocyanate, that minimizes residual diisocyanate monomers and solvent use, allowing for improved cohesion and thermal stability at lower temperatures, suitable for metal-based multilayer structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyurethane-based adhesive compositions are used, then adhesion is achieved, but high residual diisocyanate monomers are present which are toxic and require additional processing steps to remove
Solution Approach 1:
The patent changes the chemical parameters of the adhesive composition by using specific polyols (polyester polyols with hydroxyl value 50-200 mg KOH/g and polyether polyols with hydroxyl value 20-100 mg KOH/g) and controlling the NCO/OH ratio during polyaddition reaction to achieve complete reaction of diisocyanate monomers, thereby eliminating toxic residual monomers while maintaining adhesion
Solution Approach 2:
The patent converts the potentially harmful residual diisocyanate monomers into beneficial complete reaction products by optimizing the polyaddition reaction conditions, transforming the harmful factor into a benefit through complete consumption of monomers in the adhesive network
2Object-generated harmful factors
If additional processing steps are added to remove residual diisocyanate monomers, then toxicity is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent performs preliminary action by completely reacting the diisocyanate monomers during the initial polyaddition reaction through optimized conditions (specific polyol selection, NCO/OH ratio control, and reaction temperature management), preventing the formation of harmful residual monomers before the adhesive is applied, thereby eliminating the need for subsequent removal processing steps
3Strength
If adhesive composition is applied to metal materials, then bonding is achieved, but high residual diisocyanate monomers pose environmental and health concerns
Solution Approach 1:
The patent changes the chemical composition parameters by selecting specific polyol types (polyester and polyether polyols with controlled hydroxyl values) and optimizing the NCO/OH ratio to ensure complete reaction of diisocyanate monomers, thereby achieving strong bonding to metal materials while eliminating harmful residual monomers that would cause environmental and health concerns
4Ease of manufacture
If conventional adhesive compositions are used, then lamination is possible, but solvent content is high which increases environmental impact
Solution Approach 1:
The patent extracts and eliminates the harmful solvent component from the adhesive composition by developing a solvent-free formulation based on complete polyaddition reaction of diisocyanate monomers with polyols, maintaining lamination capability while removing the need for harmful solvents and reducing environmental impact
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 achieves excellent cohesion and thermal resistance, enabling the manufacture of flexible packagings that can withstand pasteurization and sterilization without significant loss of adhesion, while reducing environmental impact through minimized solvent and diisocyanate content.
Implementation Method 1
a polyurethane prepolymer having NCO endings obtained by a polyaddition reaction of at least one asymmetric diisocyanate monomer and at least one diol
Implementation Method 2
the isocyanate groups of the —NCO component react with the hydroxyl groups of the —OH component, according to a reaction referred to as crosslinking, to form a polyurethane which exists in the form of a three-dimensional network comprising urethane groups
Data Source
AI summary
The invention relates to an adhesive dual-component composition based on polyurethane, comprising an —NCO component and an —OH component such that: the —NCO component is a composition comprising: A) at least one polyurethane prepolymer comprising at least two NCO terminal groups obtained by the polyaddition reaction of at least one dissymmetric diisocyanate monomer and at least one diol, and B) at least one triisocyanate selected from isocyanurates, biurets, diisocyanate and triol adducts, and the mixtures thereof; the —OH component is a composition comprising at least one polyol; at least one of the polyols or diols is selected from polyether polyols (or polyether diols); at least one of the polyols or diols is selected from polyester polyols (or polyester diols); and the weight ratio of the quantity of polyether polyol(s) to the quantity of polyester polyol(s), defined as r4, ranges from 0.6 to 2.2.