Surface-Modified Pigment Compositions for High-Solids Coatings
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Solution Overview
Problem
Carbon black and organic pigments with conjugated keto or azomethine groups exhibit poor dispersibility and rheology, particularly in high-solids coatings, due to their point-symmetrical and mirror-symmetrical chromophores, leading to unsatisfactory performance in coating systems.
Innovation Solution
The use of specific heterocyclic compounds as modifying reagents, which form a chromophore with a divalent group consisting of a linear chain, improves the dispersibility and rheology of pigments by creating a continuous or discontinuous layer on the pigment surface, enhancing the performance in high-solids coating systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional surface modification methods are used on carbon black and organic pigments with conjugated keto or azomethine groups, then the pigment surface is modified, but the dispersibility and rheology remain poor due to the point-symmetrical and mirror-symmetrical chromophores
Solution Approach 1:
The patent applies asymmetry by introducing heterocyclic substituents with specific structures (compounds of formulae I-IV) that break the point-symmetry and mirror-symmetry of the chromophores. These asymmetric substituents create steric hindrance and prevent close packing of pigment molecules, thereby improving dispersibility in coating systems while maintaining the desired color properties
Solution Approach 2:
The patent applies local quality by modifying specific regions of the pigment molecule with heterocyclic groups at controlled positions. This localized modification affects only specific areas of the pigment surface, creating regions with different steric and electronic properties that enhance interfacial interactions with the coating matrix without altering the overall chromophore color characteristics
2Quantity of substance
If high concentration of conventional pigments is used in coating systems, then color strength is improved, but rheology and dispersibility deteriorate
Solution Approach 1:
The patent applies the intermediary principle by using heterocyclic substituents as mediating structures between the pigment core and the coating matrix. These substituents act as spacers and interfacial modifiers that facilitate better interaction with the surrounding medium, enabling higher pigment concentrations to be achieved without compromising rheological properties or processing ease
3Reliability
If pigment surface is modified with aromatic groups, then dispersibility is improved, but migration and bleeding occur
Solution Approach 1:
The patent applies composite materials by creating hybrid structures that combine heterocyclic rings with specific substituent patterns (comprising electron-donating and electron-withdrawing groups). This composite molecular architecture provides both the dispersibility benefits of aromatic modification and the stability against migration and bleeding through balanced electronic distribution and enhanced molecular rigidity
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 modified pigment compositions demonstrate excellent migration-free performance, with improved rheology, high gloss, and excellent overcoating resistance, along with negligible bleeding and enhanced light, weathering, and heat stability.
Implementation Method 1
Surface modification is obtained by linking aromatic groups including aryl and heteroaryl groups, for example imidazolyl and indolyl
Implementation Method 2
Surface modification is obtained by linking aromatic groups including aryl and heteroaryl groups
Data Source
AI summary
Pigment compositions containing organic pigments with an outstanding migration-free property and an excellent rheology at high concentration, and derivatives thereof containing heterocyclic substituents. The pigment compositions contains (a) carbon black or an organic pigment containing a chromophore Q1 of the following formula,wherein Z1 and Z2 are O or N—, C· is a carbon atom with an electron in a p orbital, and n is an integer from 1 to 4; and (b) a compound containing a chromophore of the following formula (II),wherein Q2 is an m-valent residue of carbon black or of the chromophore Q1; G1 is preferablyand R1, R2, R3, R4, R5, R6, and R8 are preferably all H; m is an integer from 1 to 4. The pigment compositions can be used as rheology modifiers, preferably for pigmented coating compositions.