Steel coils stacked in rows in an open storage yard
If coil coating does not spread in time after roll coating, the film is left with sagging and orange peel before curing; after curing the gloss on the panel comes out uneven, and the surface quality and the yield of the coil fall together.
Chemi Tech supplies leveling agents for coil coating systems such as prepainted steel coil and aluminium coil, drawn from the leveling agent KMP-4600 series; the dosage is set by the viscosity of the coating, the film thickness and the line speed. KMP-4600 lowers surface tension noticeably and governs dynamic surface tension as well, so the film spreads fully before surface drying after roll coating and the leveling window on the coil line opens up with it; it is compatible and does not interfere with intercoat adhesion, leaving room for recoating. Chemi Tech runs the leveling comparison around the coating system and the line speed, and selects the leveling agent that fits for the customer.
Advantages of Chemi Tech Leveling Agents
Chemi Tech leveling agent KMP-4600 series lowers surface tension noticeably and governs dynamic surface tension as well, so the film spreads fully before curing after roll coating and sagging and orange peel on the panel are eased with it; and its compatibility is good, it does not interfere with intercoat adhesion, and the intercoat bond of recoating and repair stays stable; it has little effect on gloss, and gloss across the panel is even; its heat stability is good, it does not decompose or yellow in the curing zone, and the colour of the finished panel stays consistent.
Industry Pain Points and Solutions
Leveling problems in coil coating mostly arise from the leveling window being squeezed by line speed; the consequence is sagging and orange peel in the film and uneven gloss on the panel.
The most difficult of them is sagging after roll coating. Coil line speeds are high, the film surface-dries before leveling is complete, and the film that has not yet spread leaves sagging on the panel. Chemi Tech's approach is to add the KMP-4600, which lowers surface tension noticeably, at the paint-mixing stage, so that the film completes its spread before curing.
The next is the evenness of gloss. When the film is under-leveled, film thickness varies from place to place on the panel, gloss comes out mottled after curing, and colour difference shows up with it. Chemi Tech runs the leveling comparison against line speed, and calibrates the addition level and the leveling window as one.
The last item is intercoat adhesion. At an addition level on the high side the leveling agent enriches at the film surface and weakens the intercoat bond of recoating. Chemi Tech's KMP-4600 is compatible and leaves room for recoating, and intercoat adhesion stays stable at normal addition levels.
Typical Conditions and Verification
Customer: a coil coating producer in Jiangsu, for the coating that goes with a prepainted steel coil roll coating line.
At this plant the coil coating worsened in sagging and orange peel after the line was sped up, gloss on the panel was uneven, and the rework rate ran high over the long term. The solution Chemi Tech leveling agent gave for this was: against the coating viscosity and the line speed, the KMP-4600 series was selected, the addition point was moved to the paint-mixing stage, the addition level was recalibrated by line speed, and the curing temperature curve was fine-tuned with it. After the adjustment was complete, sagging and orange peel on the panel eased noticeably, gloss evenness came back into the qualified range, and the rework rate came down with it.
Frequently Asked Questions
Will the leveling agent, once added, affect the recoating and repair of the coil?
It does need attention, since at an addition level on the high side the leveling agent weakens the intercoat bond of recoating. For KMP-4600, Chemi Tech has run leveling and adhesion comparisons at different addition levels and recommends only the range in which both perform steadily. The addition level depends on line speed and film thickness, and Chemi Tech gives its recommendation against the curing curve on site.