Close-up of a white powder material
If the inorganic pigment in a water-based coating is under-dispersed, the particle size is hard to narrow during grinding, the pigment re-agglomerates on standing, and the coating coarsens in the can while hiding power on the panel drops, so the storage stability and application performance of the finished product suffer together.
Chemi Tech supplies dispersants for the inorganic pigment and titanium dioxide systems of water-based coatings, drawn from the dispersant KMK-201 series; the dosage varies with pigment grade, surface treatment and target solids content. KMK-201 is a water-based dispersant that disperses titanium dioxide and inorganic pigments evenly in the system and inhibits their re-agglomeration. Chemi Tech compares dispersion performance on the basis of pigment parameters, and selects a fitted dispersant for the customer.
Advantages of Chemi Tech Dispersants
Chemi Tech dispersant KMK-201 series is designed around inorganic pigment dispersion, titanium dioxide and inorganic fillers are fully wetted and the particle size narrows after grinding; moreover, dispersion is stable, the pigment neither coarsens nor settles on standing, and the coating holds a consistent storage state; and it lowers viscosity and raises pigment loading, so hiding power rises with it; it is also compatible with water-based resins and auxiliaries, and gloss and hiding power of the film stay stable after film formation.
Industry Pain Points and Solutions
Coarsening of inorganic pigment is mostly not a matter of insufficient grinding power, but of the dispersant's stabilization of the pigment surface failing during storage; the consequence is a coarsened coating and fallen hiding power.
The most worrying point is re-agglomeration after grinding. Right after grinding the particle size narrows, but on standing for a while the pigment draws close again and the particle size rises back. Chemi Tech's answer is to add the wetting-stable KMK-201 at the feed end of the grinding stage, so that the agent is already attached when the pigment has just been wetted.
The commonest point is raised pigment content running into trouble. When the loading of titanium dioxide and inorganic fillers rises, system viscosity climbs and the resistance in grinding and transfer grows. Chemi Tech runs a dispersion comparison according to pigment grade and surface treatment, and calibrates the dosage of KMK-201 together with the grinding time.
The core difficulty lies in the drift of the storage state. A coating that has been let down coarsens and settles after standing for a while, and by the time it is sprayed its state differs from the ex-works test. Chemi Tech runs a stability comparison over the storage cycle, so that the coating holds a consistent state before spraying.
Typical Operating Conditions and Verification
Customer: a water-based coating manufacturer in Hebei, for the grinding section of titanium dioxide and inorganic fillers.
At the plant the water-based coating coarsened on standing right after grinding, there was settling at the bottom of the can, hiding power on the panel dropped, and product consistency was long constrained. The solution Chemi Tech dispersant gave for the situation was: taking pigment grade and target solids content into account, choose the KMK-201 series, set the dosing point at the feed end of the grinding stage, and grade the dosage by solids content. After the solution was in place, the particle size stayed stable on standing, settling at the bottom of the can dropped noticeably, and hiding power returned to the normal range.
Frequently Asked Questions
Once the dispersant dosage is raised, will it affect film formation and gloss of the water-based coating?
This concern has some basis; a small number of types leave components in the film while dispersing the pigment. KMK-201 has been compared for dispersion and film formation at different dosages at Chemi Tech, and only dosages where the film performs stably are recommended. The dosage depends on pigment grade, and Chemi Tech gives its dosage recommendation after grinding and spraying comparisons.