Polyurethane Coating Composition with Branched Polyester Polyol
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Solution Overview
Problem
Existing two-component polyurethane coating compositions face challenges in achieving a balance between fast drying, high hardness, excellent elasticity, scratch resistance, and robustness, often compromising one property for improvements in others.
Innovation Solution
The development of two-component polyurethane coating compositions comprising polyisocyanate, hydroxyl-containing poly(meth)acrylate polyol, and branched polyester polyol, where the acid number of the polyester polyol is greater than 30 mg KOH/g, with a specific molar mixing ratio of acid groups to hydroxyl groups and controlled levels of free diacid and tetraalcohol, optimized for solventborne systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional two-component polyurethane coating compositions are used, then scratch resistance and hardness can be achieved, but drying speed is slow and elasticity is compromised
Solution Approach 1:
The patent modifies the chemical parameters of the polyol component by using branched polyester polyols with specific acid numbers (5-30 mg KOH/g) and controlled molecular weights (500-5000 g/mol). This parameter optimization enables faster drying through improved reactivity while maintaining elasticity through controlled molecular structure and branching degree.
Solution Approach 2:
The invention creates a composite binder system combining polyacrylate polyols with branched polyester polyols in specific ratios. This composite approach integrates the fast-drying characteristics of polyacrylate with the elasticity and robustness of branched polyester, achieving synergistic effects that resolve the contradiction between drying speed and elastic properties.
2Speed
If fast-drying components are used, then drying speed improves, but ultimate hardness and scratch resistance deteriorate
Solution Approach 1:
The patent optimizes the acid number of the polyester polyol within a specific range (5-30 mg KOH/g) to balance drying speed and crosslinking density. This controlled parameter adjustment ensures sufficient reactivity for fast drying while maintaining adequate crosslinking for hardness and scratch resistance.
Solution Approach 2:
The invention employs a two-stage curing mechanism where initial fast drying occurs through rapid solvent evaporation and preliminary polymerization, followed by continued crosslinking development that enhances hardness and scratch resistance over time. This dynamic process allows both fast drying and high strength to be achieved at different time points.
3Strength
If high hardness is achieved, then scratch resistance improves, but elasticity and robustness worsen
Solution Approach 1:
The patent formulates a composite binder combining rigid polyacrylate segments (providing hardness) with flexible branched polyester polyol segments (providing elasticity). The specific molecular structure of the branched polyester with controlled acid number creates a balanced network that delivers both hardness and elastic recovery, resolving the contradiction between these properties.
Solution Approach 2:
The invention creates local structural differentiation within the coating matrix through the branched polyester polyol structure, where crosslinked regions provide hardness and scratch resistance while the branched architecture maintains flexibility and elasticity in other regions, achieving local optimization of different properties.
4Reliability
If conventional polyester polyols with low acid numbers are used, then elasticity is maintained, but drying speed and hardness development are slow
Solution Approach 1:
The patent shifts the acid number parameter of polyester polyol from conventional low values to an optimized range (5-30 mg KOH/g), which increases reactivity with isocyanate groups. This parameter change accelerates both drying speed and hardness development while the branched molecular structure preserves elastic properties through controlled flexibility.
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
These compositions exhibit enhanced drying speed, development of hardness, ultimate hardness, elasticity, scratch resistance, and robustness, providing a superior profile of properties compared to comparable compositions.
Implementation Method 1
branched polyester polyols, obtainable by polycondensation of hexahydrophthalic anhydride, trimethylolpropane, and optionally further components
Data Source
AI summary
The present invention relates to fast-drying, hard-elastic, scratch-resistant, and robust two-component polyurethane coating compositions, to their use, and to coating methods. Synthesis components in the coating compositions comprise polyisocyanate, hydroxyl-containing poly(meth)acrylate polyol, and certain branched polyester polyols, obtainable by polycondensation of hexahydrophthalic anhydride, trimethylolpropane, and optionally further components.