Polyurethane Dispersion Compatibility via Intermediary Polyols
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Prior to the development, there was a challenge in achieving good compatibility between the soft and hard segments of polyurethane dispersions containing higher molecular weight polyether diols, leading to weak film properties in sealants.
Innovation Solution
The use of low molecular weight polyether or polyester polyols in combination with hydroxyalkane carboxylic acids allows for the incorporation of high molecular weight polyether diols, resulting in stable polyurethane dispersions with exceptional flexibility, strength, and clarity, achieved through the preparation of isocyanate-terminated prepolymers and their subsequent dispersion in water with neutralization and optional chain extension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight polyether diols are incorporated into polyurethane dispersions, then film flexibility and strength are improved, but compatibility between soft and hard segments deteriorates
Solution Approach 1:
The patent employs low molecular weight polyether or polyester polyols as intermediary components that facilitate compatibility between the high molecular weight polyether diols (soft segments) and the isocyanate-terminated prepolymers (hard segments). These intermediary polyols act as compatibilizers that bridge the soft and hard segments, enabling their coexistence in a stable dispersion while maintaining the flexibility and strength benefits of the high molecular weight polyether diols.
2Adaptability or versatility
If high molecular weight polyether diols are used in polyurethane dispersions, then film flexibility is improved, but film strength deteriorates due to poor segment compatibility
Solution Approach 1:
Low molecular weight polyether or polyester polyols serve as intermediary substances that enhance the interaction between soft and hard segments. These intermediaries improve the overall film strength by ensuring proper integration of the high molecular weight polyether diols into the polyurethane matrix, thereby maintaining both flexibility and strength.
Solution Approach 2:
The patent creates a composite polyurethane dispersion system that combines high molecular weight polyether diols with low molecular weight polyether or polyester polyols and isocyanate-terminated prepolymers. This composite approach allows the synergistic combination of different molecular weight components, where each contributes specific properties: the high molecular weight component provides flexibility while the low molecular weight component ensures compatibility and strength.
3Stability of the object's composition
If conventional polyurethane dispersions are formulated without high molecular weight polyether diols, then segment compatibility is maintained, but film properties become weak
Solution Approach 1:
The low molecular weight polyether or polyester polyols function as intermediary agents that enable the incorporation of high molecular weight polyether diols while maintaining segment compatibility. These intermediaries mediate the interaction between the soft and hard segments, preventing phase separation and ensuring uniform distribution, thereby achieving both compatibility and enhanced film properties simultaneously.
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 resulting polyurethane dispersions exhibit ultra-low or no co-solvent content and provide visco-elastic film properties that were previously unattainable, with improved tensile strength, elongation, and tear resistance, making them suitable for high-performance sealants.
Implementation Method 1
an aqueous polyurethane dispersion prepared from an isocyanate-terminated prepolymer
Implementation Method 2
having at least a portion of any carboxylic acid groups neutralized
Data Source
AI summary
An isocyanate-terminated prepolymer having an isocyanate group content of about 2 to 7% by weight is provided. The prepolymer comprises the reaction product of a) at least one polyether diol having a number average molecular weight of 3000 to 5000; b) at least one active-hydrogen containing material having a number average molecular weight of 200 to 700 and containing two or three hydroxyl groups and optionally one carboxy group; c) at least one hydroxyalkane carboxylic acid having a number average molecular weight of less than about 200; d) optionally, a polyether monol having a number average molecular weight between 400-3,000; e) optionally, a polyether triol having a number average molecular weight of 3,000 to 9,000; and f) an aliphatic and/or cycloaliphatic diisocyanate.