In the formulation of automotive refinish coatings, the quality of the color paste directly determines the final coating's color accuracy, vibrancy, gloss, and long-term stability. The dispersant, as the "soul" of the color paste, is far from a one-size-fits-all choice. Facing diverse systems ranging from high-color carbon blacks to high-transparency organic pigments, and from 1K CAB to 2K PU, selecting the right dispersant requires precise alignment of pigment characteristics with resin chemistry. This article aims to clarify the logic behind dispersant selection in automotive refinish coatings and, based on common pigments and systems, provide a technical reference framework for selection.
I. The Foundation of Selection: Understanding the Two-Dimensional Needs of the System and Pigment
Selecting a dispersant for automotive refinish coatings requires first clarifying two dimensions: the coating system and the target pigment.
1.System Dimension: The mainstream systems are 1K CAB (Cellulose Acetate Butyrate) and 2K PU (Two-Component Polyurethane). Their differences in resin polarity, solvent composition, and curing mechanisms impose distinct requirements on the compatibility and anchoring group design of dispersants. For instance, a dispersant that performs excellently in CAB systems may need to be adjusted when used in PU systems.
2.Pigment Dimension: The demand for dispersant adsorption varies greatly depending on the pigment's chemical nature and surface treatment.
Carbon Black: With its high specific surface area and high surface energy, especially for high-color carbon blacks, it requires dispersants that provide strong anchoring and steric hindrance to prevent flocculation and ensure blackness. Anjeka-6050 has been repeatedly validated for excellent color development and gloss with pigments like FW200 and Special Black 6# in both 1K CAB and 2K PU systems. For applications demanding extreme blackness, Anjeka-6200 can be considered.
Organic Pigments (e.g., Phthalo Blue, PR179 Red, PV23 Violet): These are diverse in type and properties. The versatile Anjeka-6176 and Anjeka-6040 are often recommended as a starting point, covering most colored organic pigments. For demanding red pigments like PR177 and PR122, Anjeka-6164A is the preferred choice due to its ability to achieve high transparency.
White and Inorganic Pigments: Titanium dioxide (e.g., R996) and transparent iron oxides typically require dispersants that can effectively reduce viscosity, prevent flocculation, and maintain whiteness or transparency. Anjeka-6110A is a specialized choice in this area.
II. Application Scenarios: A Product Logic from General to Specific
Based on the two-dimensional analysis above, Anjeka's dispersant portfolio presents a clear, scenario-based structure:
General Solution for 2K PU Topcoats: Anjeka-6162A is positioned as a versatile choice for various pigments, providing a robust starting point for formulation development.
Color Solutions for 1K CAB and 2K PU: Anjeka-6176 and Anjeka-6040 form a "dual-safeguard" covering most organic pigments, allowing formulators to fine-tune based on specific pigment brands and batches.
High-Performance Solutions for Specific Pigments: For pigments like PR177/PR122 where extreme transparency is pursued, Anjeka-6164A is a proven solution.
Matting Powder Dispersion: When preparing high-concentration, stable matting agent pastes, wetting dispersants like Anjeka-6820 are more targeted than general-purpose dispersants.
Primer/Surfacer Solutions: Facing high-filler-load systems, the selection logic shifts to viscosity reduction and anti-settling. Anjeka-6500-50 (balancing economy and viscosity reduction) and Anjeka-6402 (focusing on anti-settling) are designed for such scenarios.
III. Experimental Validation: Data-Driven Selection Confidence
Ultimately, any selection logic must be validated by experimentation. Taking carbon black dispersion as an example, experimental data shows that in a 1K CAB system, using Anjeka-6050 to disperse different carbon blacks (BP1300 and FW200) achieved 60° gloss values exceeding 102, demonstrating excellent color development and gloss performance. Compared to reference products, it also showed advantages under the same conditions. This highlights that even for the same pigment type (e.g., carbon black), different brands or batches may respond differently to dispersants. Therefore, a "recommendation list" is just the starting point; lab-scale testing and validation are the true endpoints.
IV. Beyond the Product: A Systematic Approach to Paste Formulation
Choosing the right dispersant is only the first step. Constructing a high-performance color paste also requires consideration of:
1.Grinding Process: The timing of dispersant addition (typically before the pigment is added to the resin/solvent), grinding media, and duration all impact the final dispersion quality.
2.Compatibility Testing: The compatibility of the prepared paste with the target clearcoat or base resin must be tested to prevent issues like floating, flooding, or flocculation caused by incompatibility.
3.Storage Stability: Evaluating changes in paste viscosity, pigment settling, and flocculation through thermal storage (e.g., weeks at 40°C or 50°C) is an essential step to verify the long-term efficacy of the dispersant.
The world of color in automotive refinish coatings is intricate and complex. There is no "universal" dispersant, only "more suitable" solutions. Anjeka is committed to providing a portfolio of dispersants covering mainstream systems and pigment needs, accompanied by detailed application guidelines. If you are seeking dispersion solutions for specific pigments or systems, or wish to optimize the performance of your existing color pastes, please contact us. We offer targeted product literature and sample support to explore the technical pathways for enhancing coating quality together.
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