Carboxy-functional Polyether Basecoat Pinhole Stability
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Solution Overview
Problem
Existing multicoat paint systems face issues with pinholes due to air, solvent, and moisture inclusions, leading to visual defects, and the transition to aqueous basecoat materials is necessary for environmental sustainability.
Innovation Solution
A carboxy-functional polyether-based reaction product is developed, with specific compounds and polyethers reacting in a controlled molar ratio to form a stable basecoat material that reduces pinhole formation and enhances environmental friendliness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If aqueous basecoat materials are used to replace organic solvent-based materials, then environmental friendliness is improved, but pinhole stability deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the binder system by using carboxy-functional polyether-based reaction products with specific molecular weights (500-50,000 g/mol) and acid numbers (10-200 mg KOH/g). These parameter adjustments allow the aqueous basecoat to achieve both environmental compliance and pinhole stability by optimizing the balance between water solubility and film-forming properties.
Solution Approach 2:
The invention creates a composite binder system combining carboxy-functional polyether reaction products with specific molecular weight ranges and acid number ranges. This composite approach allows the material to simultaneously exhibit good water dispersibility (for environmental friendliness) and adequate film continuity (for pinhole stability) that neither component could achieve alone.
2Productivity
If multiple coating materials are applied successively without separate curing, then productivity is improved, but pinhole formation increases
Solution Approach 1:
The patent applies preliminary action by formulating the basecoat material with specific carboxy-functional polyether binders that pre-establish film continuity and stability before the final curing step. This preliminary formulation ensures that even when multiple coats are applied without intermediate curing, the basecoat maintains sufficient integrity to prevent pinhole formation during the combined curing process.
Solution Approach 2:
The invention provides beforehand cushioning by incorporating binders with specific molecular weight and acid number ranges that create a resilient film structure. This cushioning effect allows trapped solvents and air to escape gradually during the combined curing process without causing pinholes, thereby enabling high-productivity multi-coat application without separate curing steps.
3Ease of operation
If air, solvent, and moisture inclusions are present in the coating, then ease of application is improved, but visual appearance deteriorates
Solution Approach 1:
The patent converts the potentially harmful effect of air, solvent, and moisture inclusions into a beneficial process by using binders that allow these inclusions to be trapped temporarily during application (maintaining ease of application) and then systematically released during curing (preventing pinholes and maintaining visual appearance). The carboxy-functional polyether structure enables this controlled inclusion management.
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 new basecoat material significantly improves stability against pinholes and maintains high environmental standards, suitable for OEM finishing and automotive applications.
Implementation Method 1
there may be unwanted inclusions of air, solvent and/or moisture, which may become perceptible in the form of bubbles beneath the surface of the overall paint system, and may break open in the course of the final curing. The holes that are formed in the paint system as a result, also called pinholes
Implementation Method 2
the replacement of coating materials based on organic solvents by aqueous coating materials is becoming ever more important in order to take account of the rising requirements for environmental friendliness
Implementation Method 3
a pigmented aqueous basecoat material which comprises a carboxy-functional polyether-based reaction product which is preparable by reaction of (a) at least one compound of the formula (I) X1—Y—X2 in which X1 and X2, independently of one another, are each a functional group which is reactive toward hydroxyl groups
Data Source
AI summary
The present invention relates to a pigmented aqueous basecoat material comprising a polyether-based reaction product which is preparable by reaction of (a) at least one compound of the formula (I)X1—Y—X2 (I)in whichX1 and X2, independently of one another, are each a functional group which is reactive toward hydroxyl groups, and Y is a divalent aliphatic or araliphatic, carboxy-functional organic radical having a number-average molecular weight of 100 to 1000 g/mol,with(b) at least one polyether of the general structural formula (II)in whichR is a C3 to C6 alkylene radical and n is selected accordingly such that the polyether (b) possesses a number-average molecular weight of 200 to 4000 g/mol, where components (a) and (b) are used in the reaction in a molar ratio of 0.7/2.3 to 1.6/1.7 and the resulting reaction product possesses a number-average molecular weight of 500 to 15 000 g/mol and an acid number of 10 to 120 mg KOH/g.