Polyurethane Dispersion Alkanolamine Neutralization
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Solution Overview
Problem
Existing polyurethane dispersions used as laminating adhesives face issues with neutralization, leading to high viscosity, impaired water resistance, and reduced adhesive performance due to the use of volatile amines or alkaline bases, which react with isocyanate groups or result in coarse dispersions.
Innovation Solution
A polyurethane dispersion with anionic groups neutralized by alkanolamines containing at least two hydroxyl groups, specifically using triisopropanolamine, to achieve low viscosity and improved film formation and elasticity, while avoiding the drawbacks of volatile amines and alkaline bases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If volatile amines (e.g., triethylamine) are used to neutralize polyurethane dispersions, then the dispersion is easier to process due to lower viscosity, but the water resistance and adhesive performance are impaired
Solution Approach 1:
The patent changes the chemical structure parameter of the amine neutralizing agent from volatile low molecular weight amines to non-volatile high molecular weight alkanolamines with at least two hydroxyl groups. This parameter change resolves the contradiction by providing both low viscosity for processability and maintained water resistance, as the hydroxyl groups form hydrogen bonds that prevent water penetration while the high molecular weight prevents volatility.
2Strength
If alkaline bases are used to neutralize polyurethane dispersions, then the film hardness is significantly increased, but the water resistance and adhesive activation ability are permanently impaired
Solution Approach 1:
The patent changes the chemical nature parameter from alkaline bases to alkanolamines with hydroxyl groups. This resolves the contradiction because the hydroxyl groups provide hydrogen bonding capability that increases film hardness through intermolecular forces while simultaneously maintaining water resistance through hydrophobic interactions, unlike alkaline bases that create permanent hydrophilic sites.
Solution Approach 2:
The patent creates a composite effect by combining alkanolamine molecules that contain both basic nitrogen atoms (for neutralization) and hydroxyl groups (for hydrogen bonding). This composite molecular structure resolves the contradiction by integrating both hardness-providing and water-resistance-providing functionalities into a single neutralizing agent.
3Loss of substance
If long-chain low-volatility amines are used to neutralize polyurethane dispersions, then volatility is reduced, but the dispersion becomes very coarse or cannot be dispersed at all
Solution Approach 1:
The patent changes the molecular structure parameter by introducing at least two hydroxyl groups into the amine molecule. This resolves the contradiction because the hydroxyl groups provide strong hydrogen bonding capability that stabilizes fine dispersion, while the alkanolamine backbone maintains low volatility. The dual functional groups create a balance between dispersion stability and volatility resistance.
4Ease of manufacture
If ammonia is used to neutralize polyurethane dispersions, then neutralization is achieved, but chain termination occurs due to reaction with NCO end groups
Solution Approach 1:
The patent changes the chemical reactivity parameter by selecting alkanolamines with hydroxyl groups that have selective reactivity. The hydroxyl groups preferentially react with or coordinate to the polyurethane chains without causing chain termination, unlike ammonia which reacts with NCO end groups. This parameter change resolves the contradiction by maintaining both neutralization efficiency and polymer chain integrity.
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 solution results in polyurethane dispersions with low viscosity, enhanced water resistance, and improved adhesive strength, suitable for high-temperature applications, with storage-stable 1K systems and effective lamination of various materials.
Implementation Method 1
the polyurethane contains anionic groups which are neutralized to at least 10 mol% by alkanolamines with at least two hydroxyl groups
Implementation Method 2
alkanolamines with at least two hydroxyl groups... improved film formation and elasticity
Implementation Method 3
polyurethane dispersion containing water-emulsifiable polyisocyanates being excluded... anionic groups which are neutralized
Data Source
AI summary
The invention relates to a polyurethane dispersion which is characterized in that the polyurethane contains anionic groups, which are neutralized to at least 10 mol % by alkanolamines with at least two hydroxyl groups. Polymer dispersions that contain water-emulsifiable polyisocyanates are excluded.