Polyurethane Polymer Adhesion in Multicoat Paint Systems
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Solution Overview
Problem
Adhesion issues between basecoat and clearcoat in multicoat paint systems, particularly on metallic and plastic substrates, lead to delamination when exposed to weathering, especially in automotive refinish applications, where highly chromatic colors with high pigment content are prone to flaking and extensive delamination upon steam cleaning.
Innovation Solution
A polymer is developed by reacting dimer fatty acids with specific polyethers and polyisocyanates, along with other compounds, to create a polyurethane-based pigmented aqueous basecoat material that enhances adhesion between the basecoat and clearcoat, and between the basecoat and substrate, maintaining adhesion even after weathering exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyurethane dispersions are used in aqueous basecoat materials, then the coating process is simple and widely practiced, but adhesion problems occur between basecoat and clearcoat, leading to delamination when exposed to weathering
Solution Approach 1:
The patent modifies the chemical composition parameters of the polyurethane dispersion by incorporating specific polyether components (formula I and II) with controlled molecular weights and ratios. This changes the polymer structure to enhance adhesion properties while maintaining compatibility with clearcoat systems, resolving the delamination issue without altering the basic coating process
Solution Approach 2:
The invention creates a composite polyurethane system by combining multiple components: dimer fatty acids, specific polyethers (formula I and II), and other functional compounds. This composite structure provides both the adhesion enhancement needed to prevent delamination and the compatibility required for clearcoat bonding, eliminating the harmful flaking effect
2Illumination intensity
If highly chromatic colors with high pigment content are used in basecoat, then color intensity and aesthetic appeal are improved, but the paint film becomes prone to flaking and extensive delamination upon steam cleaning
Solution Approach 1:
The patent adjusts the polymer composition parameters to include specific ratios of polyether components that enhance adhesion without interfering with pigment dispersion. This allows high pigment content formulations to maintain both color intensity and adhesion stability, preventing steam cleaning-induced delamination
Solution Approach 2:
The modified polyurethane dispersion acts as an intermediary between the high-pigment basecoat and the clearcoat system. Its enhanced adhesion properties create a stable interface that prevents flaking even when the basecoat contains high levels of chromatic pigments, allowing the desired color intensity to be achieved without compromising durability
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 polymer significantly improves adhesion properties, reducing flaking and delamination in weathered refinishes, ensuring a stable paint film on metallic and plastic substrates, even under steam cleaning conditions.
Implementation Method 1
A polymer which is preparable by reacting (A) at least one polymer, preparable by reacting (a) dimer fatty acids with (b) at least one polyether... (D) at least one polyisocyanate
Data Source
AI summary
The present invention relates to a polymer, preparable by reactingat least one polymer, preparable by reacting (a) dimer fatty acids with at least (b) one polyether having a C3 to C6 alkylene radical and a number-average molecular weight of 450 to 2200 g/mol, components (a) and (b) are used in a molar ratio of 0.7/2.3 to 1.3/1.7, and the resulting polymer has a number-average molecular weight of 1500 to 5000 g/mol and an acid number <10 mg KOH/a, at least one polyether with a C3 to C6 alkylene radical and with a number-average molecular weight of 250 to 3000 g/mol, at least one compound having at least one anionic group and/or at least one functional group capable of forming anions,and at least one, more particularly at least two, isocyanate-reactive functional groups, at least one polyisocyanate, andoptionally at least one monool or diol, at least one compound having more than two isocyanate-reactive functional groups, and optionally neutralizing the groups of component (C) that are capable of forming anions.