Waterproof Breathable PU Dispersion With Low Viscosity
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Solution Overview
Problem
Current polyurethane dispersions for waterproof and water vapor permeable coatings have high viscosities and are prone to hydrolysis, leading to reduced laundry-proofness and processing difficulties.
Innovation Solution
An aqueous polyurethane dispersion is developed using a polyol component comprising aliphatic polyester polyols and a polyisocyanate component with ≥ 50 weight-% dicyclohexylmethane diisocyanate, combined with an isocyanate-reactive component containing sulfonate groups, which improves the polymer's chain extensibility and laundry-proofness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyoxyalkylene units are used to facilitate water vapor transport, then water vapor permeability is improved, but viscosity increases and laundry-proofness deteriorates due to hydrolysis
Solution Approach 1:
The patent changes the chemical composition parameters by replacing polyoxyalkylene units with aliphatic polyester polyol units. This substitution maintains the hydrophilic character needed for water vapor transport while eliminating the excessive viscosity and hydrolysis problems associated with polyoxyalkylene units. The specific parameter change involves using polyester polyols with controlled molecular weights and compositions to achieve the desired balance between permeability and processability.
Solution Approach 2:
The patent creates a composite polymer structure combining polyurethane segments with aliphatic polyester polyol soft segments. This composite approach integrates the breathability function of hydrophilic segments with the durability and processability of polyester-based hard segments, achieving both water vapor permeability and resistance to hydrolysis.
2Reliability
If conventional polyurethane dispersions are used, then water vapor permeability is achieved, but processing becomes difficult due to high viscosity
Solution Approach 1:
The patent optimizes the molecular weight and structural parameters of the polyester polyol components to achieve lower viscosity. By carefully selecting the chain length, branching, and functional group density of the aliphatic polyester polyol, the formulation achieves both adequate water vapor permeability and improved processability for coating applications.
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 dispersion results in coatings with high water vapor permeability and enhanced laundry-proofness due to the use of non-hydrophilic polyester polyols, reducing viscosity and improving processing characteristics.
Implementation Method 1
The invention provides a process for the preparation of aqueous polyurethane dispersions with improved laundry-proofness. The process comprises the steps of: (a) preparing an isocyanate-functional polyurethane prepolymer by reacting a polyol component with a polyisocyanate component
Implementation Method 2
reacting the isocyanate-functional polyurethane prepolymer A) with an isocyanate-reactive component B)
Data Source
AI summary
Aqueous polyurethane dispersion for waterproof breathable coatings An aqueous polyurethane dispersion comprises a polyurethane polymer obtainable by the reaction of an isocyanate-functional polyurethane prepolymer A) with an isocyanate-reactive component B), wherein the isocyanate-functional prepolymer A) is obtainable by the reaction of a mixture comprising: apolyol component comprising a polyester polyol obtainable by the reaction of a mixture comprising an aliphatic dicarboxylic acidand at least one diol selected from the group consisting of linear aliphatic diolsand a branched aliphatic diols; and a polyisocyanate component comprising >=50 weight-%, based on the total weight of polyisocyanates, of dicyclohexylmethane diisocyanate. The isocyanate-reactive component B) comprises a compound comprising sulfonate groups which is employed in an amount of >=3,5 weight-% to <=10 weight-%, based on the total weight of the polyol component, the polyisocyanate component and the isocyanate-reactive component B).The invention also concerns the use of such an aqueous polyurethane dispersion for coatings, a method of manufacturing a coated substrate and to a coated substrate.