Coating Compositions Using Composite Polyols for Scratch Resistance
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Solution Overview
Problem
Current 2K polyurethane coating compositions for automotive finishes face challenges in achieving improved scratch resistance without compromising resistance to solvents and acids, particularly in dark colors and on heat-sensitive substrates.
Innovation Solution
The use of specific combinations of aliphatic oligocarbonate polyols, oligoester polyols, and hydroxy-functional polyacrylate polyols, along with reactive polyisocyanate crosslinkers, to create coating compositions that enhance scratch resistance while maintaining or improving resistance to solvents and acids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the elasticity of the clear lacquer layer is increased to improve reflow behavior, then scratch resistance is improved, but surface hardness and resistance to solvents and acids is impaired
Solution Approach 1:
The invention changes the chemical composition parameters of the polyol component by specifying exact proportions of polyacrylate (60-95 wt%), polyester (5-30 wt%), and polycarbonate (1-20 wt%), along with controlled hydroxyl numbers (20-125 mg KOH/g) and molecular weights, to achieve optimal balance between elasticity and chemical resistance
Solution Approach 2:
The invention uses a composite polyol system combining three different polyol types (polyacrylate, polyester, and polycarbonate) with specific functional groups and molecular weight ranges, where each component contributes different properties: polyacrylate provides base elasticity, polyester enhances reflow, and polycarbonate improves chemical resistance
2Strength
If polyester content is increased to improve elasticity, then reflow behavior is improved, but resistance to acids is impaired
Solution Approach 1:
The invention precisely controls the polyester content within 5-30 wt% range and limits polycarbonate to 1-20 wt%, while maintaining high polyacrylate content (60-95 wt%), to achieve the optimal balance between reflow behavior and acid resistance
Solution Approach 2:
The invention introduces polycarbonate polyol as an intermediary component that mediates between the conflicting requirements of polyester (for elasticity) and acid resistance, with polycarbonate providing enhanced chemical stability while working synergistically with the polyester-polyacrylate matrix
3Ease of operation
If polyacrylate-polyester mixtures are used with low crosslinking densities, then viscosity is reduced, but resistance to solvents and chemicals is impaired
Solution Approach 1:
The invention optimizes the hydroxyl number parameter to 20-125 mg KOH/g and controls molecular weights (Mn: 200-5,000 g/mol for polyacrylate, 200-2,000 g/mol for polyester) to achieve low viscosity while maintaining adequate crosslinking density through the specified polyol composition ratios
Solution Approach 2:
The invention creates a composite polyol system where the synergistic interaction between polyacrylate, polyester, and polycarbonate components provides both low viscosity (through controlled molecular weight and hydroxyl number) and high chemical resistance (through the diversified chemical structure and crosslinking network)
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 described coating compositions exhibit significantly improved scratch resistance and retain excellent resistance to solvents and acids, even after frequent washing cycles, without compromising surface hardness or chemical resistance.
Implementation Method 1
coating compositions comprising a polyol component consisting of a) from 60 to 95 wt. % hydroxy-functional polyacrylate polyols, b) from 5 to 30 wt. % oligoester polyols, and c) from 1 to 20 wt. % aliphatic oligocarbonate polyols, and one or more polyisocyanate crosslinkers that are reactive towards OH groups
Data Source
AI summary
The present invention relates to novel coating compositions comprising polyisocyanates, aliphatic oligocarbonate polyols, oligoester polyols and polyacrylate polyols, to a process for their production and to their use in the production of coatings.