Multilayer Coated Metal Effect Pigments for Gassing and Shear Stability
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Solution Overview
Problem
Existing metal effect pigments, particularly in waterborne coatings, face challenges with corrosion and mechanical stability, leading to hydrogen gas evolution and poor performance in aggressive tests like the Waring-Blender test, which simulates shear forces in automotive circulation lines.
Innovation Solution
A multi-layer coating sequence is applied to metal effect pigments, comprising a discontinuous or continuous Mo-oxide layer, an inorganic SiO2 layer, a hybrid layer modified by diphenyl or phenyl silane, and optionally a top-coat of organofunctional silanes, to enhance gassing stability and mechanical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dense silica coating is applied to metal effect pigments, then gassing stability is improved, but mechanical stability under shear forces deteriorates
Solution Approach 1:
The patent applies a composite coating structure consisting of an inner silica layer (providing gassing stability) and an outer hybrid organic-inorganic layer (providing mechanical stability). This multi-layer composite approach allows each layer to fulfill its specific function: the silica layer prevents hydrogen evolution, while the hybrid layer with cross-linked organic polymers provides resistance to shear forces and mechanical impact.
Solution Approach 2:
The coating is segmented into functionally distinct layers: an inner silica coating layer for corrosion protection and gassing stability, and an outer hybrid layer for mechanical strength. This segmentation allows optimization of each layer for its specific purpose without compromising the other.
2Strength
If hybrid organic-inorganic layers are used to improve mechanical stability, then resistance to shear forces is improved, but gassing stability deteriorates
Solution Approach 1:
The coating is segmented into functionally distinct layers: an inner silica coating layer for corrosion protection and gassing stability, and an outer hybrid layer for mechanical strength. This segmentation allows optimization of each layer for its specific purpose without compromising the other.
Solution Approach 2:
The patent applies a composite coating structure consisting of an inner silica layer (providing gassing stability) and an outer hybrid organic-inorganic layer (providing mechanical stability). This multi-layer composite approach allows each layer to fulfill its specific function: the silica layer prevents hydrogen evolution, while the hybrid layer with cross-linked organic polymers provides resistance to shear forces and mechanical impact.
3Reliability
If multiple coating layers are applied to enhance performance, then gassing stability and mechanical durability are improved, but manufacturing complexity increases
Solution Approach 1:
The silica layer is formed first as a preliminary step to establish the corrosion-resistant base layer before applying the hybrid organic-inorganic coating. This preliminary action ensures that the inner layer provides gassing stability before the outer mechanical protection layer is added.
Solution Approach 2:
The patent applies a composite coating structure consisting of an inner silica layer (providing gassing stability) and an outer hybrid organic-inorganic layer (providing mechanical stability). This multi-layer composite approach allows each layer to fulfill its specific function: the silica layer prevents hydrogen evolution, while the hybrid layer with cross-linked organic polymers provides resistance to shear forces and mechanical impact.
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 coated pigments demonstrate improved gassing stability and mechanical durability, passing enhanced Waring-Blender tests with minimal optical property distortion, making them suitable for aggressive waterborne coating applications.
Implementation Method 1
The silica layer is formed by sol-gel synthesis
Implementation Method 2
forming a hybrid layer on layer b1) by sol-gel reaction of a tetraalkoxy silane of formula Si(OR)4 (I) with a diphenysilane of formula Ph2Si(OR′)2, (IIa), a phenyl silane of formula PhSi(OR′)3 (IIb) or mixtures thereof
Implementation Method 3
a first layer of molybdenum oxide prior to the silica coating
Data Source
AI summary
This invention involves a coated flaky metal effect pigment comprising a metal effect flake as substrate coated by the following consecutive coating sequences: a) optionally a discontinuous or a continuous layer of Mo-oxide, b1) an inorganic metal oxide layer comprising mainly SiO2, c1) a hybrid layer comprising SiO2 modified by a diphenyl silane, a phenylsilane or mixtures thereof or c2) a hybrid layer comprising SiO2 modified by a diphenyl silane, a phenylsilane or mixtures thereof, b2) an inorganic metal oxide layer comprising mainly SiO2, and d) optionally a further top-coat of organofunctional silanes, titanates, aluminates or zirconates.