Layer separation is a common issue when performing solvent-based paint mixing in industrial paint production. This defect strongly affects gloss, color stability, and the durability of the coating. Separation can occur quickly if the additive is not compatible with the resin system. Let’s explore the mechanisms that trigger layer separation and review proper mixing techniques to keep the paint system stable.
CAUSES OF LAYER SEPARATION IN SOLVENT-BASED PAINTS WHEN ADDING ADDITIVES
Incompatibility between resin and additives
Incompatibility is a major cause of phase separation in solvent systems. When functional groups do not match, the additive is pushed out of the resin network. Small clusters form first, then develop into larger gel structures. These gels break the internal structure and create visible phase separation.
Alkyd, acrylic, and NC systems are highly sensitive to this issue when the wrong additive type is used. Gel regions also expand quickly under strong agitation. They create weak networks and drag surrounding particles with them. This accelerates the separation process significantly.
Differences in polarity and solubility parameters
Polarity determines how well the resin and additive blend together. When the polarity gap is too large, the solvent cannot bring the additive into a stable dissolved state. The paint splits into two clear phases—one solvent-rich layer rises while the heavier fraction settles at the bottom.
This defect is common in NC and PU solvent-based systems. Polarity mismatch also weakens long-term stability. The mixture loses balance only hours after agitation. In many systems, a light surface haze can appear as an early sign of separation.
Improper base viscosity
Viscosity controls how well an additive disperses through the system. If the base is too thin, the additive fails to stabilize due to limited shear. If the base is too thick, the additive forms lumps immediately at the contact point. Both situations lead to strong phase separation during storage.
Adjusting viscosity before mixing is essential. A suitable viscosity creates a more stable dispersion structure. Solvent-based paint systems are very sensitive to temperature-related viscosity shifts. Even small changes can significantly affect stability.
CORRECT ADDITIVE MIXING PROCEDURE FOR SOLVENT-BASED PAINTS
Check compatibility before mixing
Compatibility checks help reduce production risks. Small tests such as rub-up or solubility checks reveal the additive’s blending behavior. If cloudiness or light gelation appears, the additive or solvent composition must be adjusted. Early testing is always more cost-effective than losing an entire batch. It also helps optimize formulation cost. Plants can avoid operational errors that arise during scaling. These small tests provide highly accurate evaluations of system behavior.
Adjust base viscosity before adding additives
A stable viscosity ensures better wetting and dispersion of the additive. Each resin system has an optimal viscosity range. Many manufacturers skip this step and face early separation. Proper viscosity ensures a balanced environment for additive distribution. It also improves the smoothness of the final coating. Systems remain more stable when viscosity stays within the recommended window. This adjustment supports consistent performance in large-scale operations.
Add additives in incremental stages
Additives should never be dumped in all at once because this easily causes “system shock.” Shock disrupts the temporary structure and produces local phase separation. Dividing the additive into smaller increments helps the system adapt gradually. After each addition, steady mixing is required for a few minutes. This method increases uniformity and enhances storage stability. Incremental dosing is especially useful for additives that dissolve slowly.
ADDITIVES THAT HELP REDUCE LAYER SEPARATION RISK
Certain additives can support the stability of solvent-based systems under specific conditions. Compatibilizers help reduce polarity gaps between resins and other additives. Wetting agents improve the distribution of additives throughout the mixture. Some co-solvents expand the solvent’s solubility range and enhance overall system compatibility.
However, these additives serve only as supportive tools and cannot replace proper mixing procedures. Therefore, correct technique remains the key factor in preventing layer separation during solvent-based paint mixing in industrial production lines.
VICHEM – OFFICIAL DISTRIBUTOR OF LEADING CHEMICAL ADDITIVE BRANDS SUCH AS COVESTRO, SINOPEC, BUHLER… IN VIETNAM
Vichem is the official distributor of chemical additive products from leading global brands such as Covestro, Sinopec, and Buhler in the Vietnamese market. We not only supply high-quality products but also deliver international-standard technical support.
- Technical consulting: Supporting customers in selecting the right product for specific applications.
- Color-matching tests: Vichem’s experts conduct color evaluation to meet design requirements.
- Application support: Assisting customers during implementation to ensure optimal process performance.
For more information, please contact us through the channels below:
📞 Hotline: 08 1790 1790
📧 Email: contact@vichem.vn
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