Open pigment cans in various colours in a tinting room
Leave an epoxy primer to stand for a few days after it is made up and the titanium dioxide settles, a hard cake forms at the bottom of the can that cannot be stirred back, the fineness goes out of specification once it coarsens back, hiding power is short when it is sprayed, and the batch of material is very likely written off.
Chemi Tech makes dispersants for systems such as epoxy primers and waterborne industrial coatings, drawn from the dispersant KMK-130 series. How a grade is matched also depends on the type of pigment and filler, the resin system and the target pigment loading. KMK-130 is a polymeric dispersant that holds the pigment and filler surface through its anchoring groups, does not desorb under high shear grinding, holds both titanium dioxide and heavy fillers steadily, and brings a substantial viscosity reduction.
Advantages of Chemi Tech Dispersants
Chemi Tech dispersant KMK-130 series holds the pigment and filler surface through its anchoring groups, does not desorb under high shear grinding, and a finished primer sits for a month without coarsening back or sedimenting at the bottom. The viscosity reduction is substantial as well: at the same pigment and filler loading the paste still flows and the bead mill current holds steady. Anti-settling is good, too, so fineness is consistent top to bottom in the can and no half-hour of stirring is needed on opening. Its coverage of titanium dioxide and heavy fillers is broad, so changing brand does not mean tearing the formulation down and starting again. The dosage is added at a small percentage of pigment and filler weight, so the overall cost stays controllable. A note from Chemi Tech: the behaviour above comes from a typical epoxy primer grinding condition. When the pigment and filler type or the resin system is changed in bulk, the results move, so a small trial has to be run before scaling up.
Industry Pain Points and Solutions
With a primer coarsening back and sedimenting at the bottom, what worries people most is fineness claims coming back one after another; the root is not in the stirring, it is in whether the dispersant and the pigment and filler hold on to each other.
The first thing to go wrong is titanium dioxide being hard to hold. Titanium dioxide has high surface energy, and if the dispersant is the wrong choice the fineness lands on target and then agglomerates back after a few days. Chemi Tech runs a round of anchoring validation on each pigment and filler in use, and the formulation follows the pigment and filler.
The problem that follows is heavy fillers settling out because of their density. Heavy fillers settle quickly, and if the dispersant only reduces viscosity without anti-settling, the bottom of the can still cakes. Chemi Tech's approach is to look at viscosity reduction and anti-settling together: hold the anchoring first, then talk about suspension.
The last problem is changing brand without changing formulation. Switch a titanium dioxide of the same class to another brand and the surface treatment is different, so a dispersant that used to hold stops holding and flooding and floating appear. Chemi Tech's approach is a brand-by-brand anchoring comparison with several dispersants run side by side. From the anchoring comparison to the storage stability, the research department at Chemi Tech will recommend against your actual formulation.
Typical Conditions and Verification
Customer: an industrial coatings enterprise in Guangdong, applying it to the grinding and storage stages of epoxy primer.
The epoxy primer from this plant was fine on the day it was made up, then the titanium dioxide settled after a few days, the bottom of the can caked, the fineness went out of specification, and there were a good many returns. The solution offered by Chemi Tech dispersant was: against the pigment and filler brand and the resin system, a suitable grade was selected from the KMK-130 series, a blank comparison was run first to confirm the problem sat at the anchoring layer, and then a pilot run was made on the bead mill. After the change the primer held its fineness for a month, the bottom of the can no longer caked, and the hiding power of the tinted coating came back into the normal range.
Frequently Asked Questions
If the titanium dioxide brand changes, does the dispersant have to change with it?
Not necessarily, but it must be validated: once the pigment and filler surface treatment changes, a dispersant that used to hold may stop holding, and both fineness and storage stability are affected. The KMK-130 Chemi Tech supplies to coating plants has been put through a brand-by-brand anchoring comparison, and Chemi Tech will settle the match on the basis of the data.