Polyurethane Dispersion Shear Stability via Ethoxylated Fatty Alcohols
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Solution Overview
Problem
Aqueous polyurethane dispersions face issues with shear stability and electrolyte stability, leading to coagulum formation and foaming problems during high-shear applications and exposure to increased electrolyte concentrations, which impairs industrial use and affects adhesive properties.
Innovation Solution
Incorporating 0.5-2% by weight of ethoxylated fatty alcohols as nonionic emulsifiers in the dispersions enhances both shear stability and electrolyte stability without significantly increasing foam development and deteriorating adhesive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If ionic groups or functional groups convertible into ionic groups are incorporated into polyurethane dispersions to achieve colloidal stability, then colloidal stability is sufficient for many technical adhesive applications, but shear stability deteriorates leading to coagulate formation under high shear forces
Solution Approach 1:
The patent introduces a new parameter (non-ionic emulsifier content) to optimize the system. By adding 0.1-5 wt% non-ionic emulsifier, the dispersion achieves both colloidal stability and shear stability without coagulate formation under high shear forces, representing a parameter change in the composition to resolve the contradiction.
Solution Approach 2:
The patent creates a composite stabilization system combining ionic groups (for colloidal stability) with non-ionic emulsifiers (for shear stability). This composite approach allows the dispersion to maintain stability under both static and high-shear conditions, resolving the contradiction between colloidal stability and shear stability.
2Adaptability or versatility
If electrolyte concentration is increased in polyurethane dispersions, then adhesive formulation flexibility is improved, but colloidal stability deteriorates leading to coagulate formation
Solution Approach 1:
The patent introduces non-ionic emulsifiers as a new parameter to counteract the destabilizing effect of electrolytes. This allows the formulation to maintain colloidal stability even when electrolyte concentration is increased for formulation flexibility, resolving the contradiction between adaptability and stability.
Solution Approach 2:
The non-ionic emulsifier acts as an intermediary substance that mediates between the ionic polyurethane particles and the electrolyte-rich environment. It provides a protective interface that prevents electrolyte-induced coagulation while allowing formulation flexibility, thus resolving the contradiction.
3Reliability
If emulsifiers are added to improve shear stability, then shear stability is significantly improved, but foaming tendency increases leading to coating defects
Solution Approach 1:
The patent optimizes the emulsifier parameters by selecting non-ionic types with specific molecular weight ranges (200-5000) and controlling the content at 0.1-5 wt%. This parameter optimization provides sufficient shear stability while minimizing foaming tendency, resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
The patent applies different functional properties to different aspects of the emulsifier system. The emulsifier provides shear stability where needed (at the particle interface) while maintaining low foaming tendency in the bulk phase, achieving local quality differentiation to resolve the contradiction.
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 addition of ethoxylated fatty alcohols significantly improves the stability of polyurethane dispersions, reducing coagulum formation and foaming, while maintaining adhesive properties, thus ensuring reliable performance in industrial applications.
Implementation Method 1
aqueous adhesive dispersion containing certain dispersed polyurethanes and ethoxylated fatty alcohols as emulsifiers
Implementation Method 2
The colloidal stability of aqueous polyurethane dispersions is typically achieved by the copolymerization of compounds with ionic groups
Implementation Method 3
without noticeably increasing the foaming of the dispersion during processing
Implementation Method 4
The colloidal stability of aqueous polyurethane dispersions is typically achieved by the copolymerization of compounds with ionic groups or by the incorporation of functional groups that can be converted into ionic groups
Implementation Method 5
Such aqueous polyurethane dispersions are described, for example, in WO 2007/028760, WO 06/087348, and WO 06/087317
Data Source
AI summary
The invention relates to aqueous adhesive dispersions, containing dispersed polyurethanes and ethoxylated fatty alcohols as emulsifiers. The polyurethanes are composed of certain organic diisocyanates, dihydroxy compounds, selected from certain polyester diols and polyether diols and compounds having groups that are reactive to isocyanate groups and at least one ionic group. The adhesive dispersions can be used as lamination adhesives, for example for composite film lamination or for the lamination of rigid molded bodies with flexible decorative films.