Waterborne Two-Component Polyurethane Composition for Extended Pot Life
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Solution Overview
Problem
Waterborne two-component polyurethane compositions face challenges with insufficient pot life and gloss loss during storage, particularly when using non-modified isocyanates, which are preferred for chemical and water resistance.
Innovation Solution
A two-component polyurethane composition comprising a hydroxyl group-containing acrylic emulsion polymer and a specific branched polyether polyol with a polyisocyanate, optimized for extended pot life and gloss retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-modified polyisocyanates are used in waterborne two-component polyurethane compositions, then chemical and water resistance properties are improved, but pot life is insufficient and gloss loss occurs during storage
Solution Approach 1:
The patent introduces a water-soluble polyol as an intermediary substance that mediates between the non-modified polyisocyanate and water. This polyol contains hydrophilic groups that enhance water solubility while maintaining the chemical reactivity needed for polyurethane formation, thereby extending pot life without compromising the chemical and water resistance provided by non-modified polyisocyanates
Solution Approach 2:
The patent modifies the molecular weight and hydroxyl value parameters of the polyol component to optimize performance. By selecting specific ranges for molecular weight (1,000-10,000 g/mol) and hydroxyl value (20-200 mg KOH/g), the composition achieves extended pot life through controlled reaction kinetics while maintaining the desired chemical resistance properties
2Ease of manufacture
If non-modified polyisocyanates are used, then cost is reduced, but gloss retention during storage deteriorates
Solution Approach 1:
The water-soluble polyol acts as a mediator that prevents premature foaming and gloss loss during storage. It controls the rate of isocyanate-water reaction, maintaining composition stability and gloss retention (above 75% after 3 hours at 35°C) while allowing the use of cost-effective non-modified polyisocyanates
3Duration of action of moving object
If hydrophilic modified isocyanates are used, then pot life is extended, but chemical and water resistance properties deteriorate
Solution Approach 1:
Instead of modifying the isocyanate to be hydrophilic (which compromises chemical resistance), the patent inverts the approach by making the polyol component hydrophilic. This allows extended pot life through improved water solubility and controlled reaction kinetics, while the non-modified polyisocyanate retains its superior chemical and water resistance properties
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 composition achieves a 60-degree gloss of higher than 75 after 3 hours at 35°C, maintaining acceptable initial gloss and distinctness of image, while providing extended pot life.
Implementation Method 1
Incorporation of isocyanates with hydrophilic modification ('hydrophilic isocyanates') into two-component polyurethane coating compositions may extend pot life due to better dispersion in water than non-modified polyisocyanates
Implementation Method 2
a polyisocyanate
Data Source
AI summary
A two-component polyurethane composition contains: (A) an aqueous dispersion comprising: a hydroxyl group-containing acrylic emulsion polymer comprising, by weight based on the weight of the hydroxyl group-containing acrylic emulsion polymer, from 5%to 50%of structural units of a hydroxy-functional alkyl (meth) acrylate; and from 2%to 20%, by weight based on the weight of the hydroxyl group-containing acrylic emulsion polymer, of a branched polyether polyol; where the branched polyether polyol has a hydroxyl functionality of from 4 to 10 and a molecular weight per branch of from 1200 to 2500 grams per mole, and contains from 20%to 40%of ethylene oxide units, by weight based on the weight of the branched polyether polyol; and (B) a polyisocyanate.