Polyurethane Coating Agent Moisture Permeability Flexibility
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Solution Overview
Problem
Existing coating agents for forming hydrophilic polyurethane resin films struggle to achieve a balance between moisture permeability, flexibility, and tensile strength, and often have inadequate storage stability of the isocyanate group-containing prepolymer.
Innovation Solution
A coating agent comprising an isocyanate group-containing prepolymer obtained by reacting a polyol mixture with a polyisocyanate compound, where the polyol mixture consists of polyoxyalkylene polyols with varying hydroxy groups and oxyethylene content, achieving an average number of hydroxy groups between 2.2 and 2.6 and a molecular weight per hydroxy group between 1,500 and 10,000, along with a preferred ratio of isocyanate groups to hydroxy groups of 3.0 to 4.5.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the average number of hydroxy groups of the polyol mixture is increased to improve tensile strength, then the tensile strength is improved, but the flexibility tends to decrease
Solution Approach 1:
The patent applies parameter changes by precisely controlling the average number of hydroxy groups within the range of 2.2 to 2.6 and the molecular weight per hydroxy group within 1,500 to 10,000. This optimized parameter range enables the coating layer to achieve both improved tensile strength and maintained flexibility, resolving the contradiction between these two properties.
2Stability of the object's composition
If the storage stability of the isocyanate group-containing prepolymer is improved, then the storage stability is improved, but this may require compromising other performance properties
Solution Approach 1:
The patent achieves improved storage stability while maintaining performance properties through parameter changes in the polyol mixture composition. By optimizing the average number of hydroxy groups (2.2 to 2.6) and molecular weight per hydroxy group (1,500 to 10,000), the prepolymer exhibits both enhanced storage stability and satisfactory coating performance.
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 coating layer or film exhibits enhanced moisture permeability, flexibility, and tensile strength, while the isocyanate group-containing prepolymer demonstrates improved storage stability.
Implementation Method 1
an isocyanate group-containing prepolymer obtainable by reacting a polyol mixture (A) and a polyisocyanate compound (B)
Implementation Method 2
The layer of this hydrophilic polyurethane resin absorbs moisture from a high humidity side and discharges moisture to a low humidity side thereby to provide a moisture permeability
Data Source
AI summary
To provide a coating agent capable of forming a coating layer or film excellent in moisture permeability, flexibility and tensile strength.A coating agent comprising an isocyanate group-containing prepolymer obtainable by reacting a polyol mixture (A) and a polyisocyanate compound (B), wherein the polyol mixture (A) is a mixture of at least two polyoxyalkylene polyols which are different in the number of hydroxy groups or the hydroxy value, and said mixture has an average number of hydroxy groups being from 2.2 to 2.6, a molecular weight per hydroxy group being from 1,500 to 10,000 and an oxyethylene group content being at least 60 mass %.