An aqueous dispersion of polyurethane
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Solution Overview
Problem
Existing aqueous dispersions of polyurethane face issues with gelation, increased viscosity, and reduced solid content due to the presence of abundant hydrophilic groups, leading to decreased coat thickness and waterproofness.
Innovation Solution
Incorporating a multifunctional polyether polyol with a star structure and controlled hydrophilic group content in the aqueous dispersion of polyurethane, ensuring good dispersity and balanced waterproof and moisture permeability, achieved through a specific reaction mixture and process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If abundant hydrophilic groups are incorporated into polyurethane dispersion to improve moisture permeability, then moisture permeability is improved, but viscosity increases and solid content decreases
Solution Approach 1:
The patent changes the chemical structure parameters of the polyol component by using polyols with specific hydroxyl values (40-180 mg KOH/g) and molecular weights (500-3000 g/mol), and by controlling the ratio of polyether polyol to polyester polyol (1:4 to 4:1), thereby achieving optimal balance between moisture permeability and viscosity without requiring abundant hydrophilic groups
Solution Approach 2:
The patent uses a composite polyol system combining polyether polyol and polyester polyol in specific ratios, where polyether polyol provides moisture permeability and polyester polyol controls viscosity, achieving synergistic effect that resolves the contradiction between the two properties
2Object-affected harmful factors
If abundant hydrophilic groups are incorporated into polyurethane dispersion to improve moisture permeability, then moisture permeability is improved, but solid content decreases
Solution Approach 1:
The patent optimizes the hydroxyl value parameter of the polyol (40-180 mg KOH/g) and the NCO/OH ratio (0.8-1.2) to control the degree of polymerization and crosslinking, thereby maintaining high solid content (30-70 wt.%) while achieving good moisture permeability through the polyether/polyester polyol ratio
3Object-affected harmful factors
If polyurethane dispersion is used to form waterproof coating, then waterproofness is improved, but coat thickness decreases due to high viscosity
Solution Approach 1:
The patent adjusts the viscosity parameters of the polyurethane dispersion by controlling the polyol molecular weight (500-3000 g/mol) and hydroxyl value, as well as the polyether/polyester polyol ratio, thereby enabling application of thicker coats while maintaining waterproofness through the optimized composition
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 a polyurethane dispersion with low viscosity, high solid content, and enhanced moisture permeability, providing a thick coat with improved waterproofness and adhesion, while maintaining stability and washing resistance.
Implementation Method 1
comprising a polyurethane polymer which is obtained by a reaction of a reaction mixture comprising a polyurethane prepolymer and an isocyanate-reactive component
Implementation Method 2
introducing water prior to, during or after step b to obtain said aqueous dispersion of polyurethane
Data Source
AI summary
The present invention relates to an aqueous dispersion of polyurethane and a method for 5 preparing the same, use thereof in a coating composition, and a coated product. The aqueous dispersion of polyurethane comprises a polyurethane polymer which is obtained by a reaction of a reaction mixture comprising a polyurethane prepolymer A) and an isocyanate-reactive component B), said polyurethane prepolymer A) being obtained by a reaction comprising the following components: A1) a polyisocyanate which has a 10 functionality of not less than 2; and A2) a multifunctional polyether polyol which has a functionality of not less than 3 in an amount of 1% to 30% by weight, based on the amount of said reaction mixture as 100% by weight. The aqueous dispersion of polyurethane according to the present invention is well dispersed, and is capable of forming a coat with good waterproof, moisture permeability and washing resistance.