Blue colour-coated steel roofing in service

Once the roller coater on a coil coating line is sped up, the paint's flow-out on the steel strip can no longer keep pace with the curing cycle; orange peel and roll marks recur coil after coil, the ripples on the panel show clearly under side light, and downgraded and repainted coils multiply with it.

Chemi Tech offers the KMP-4600 series leveling agent for colour-coated steel and aluminium coil coating, with the dosage adjusted flexibly according to the paint's solids content and the roller line speed. This grade is a leveling agent dedicated to waterborne systems, with a pronounced effect in lowering surface tension, so the flow-out window on a coil line opens up with it; it has little influence on intercoat adhesion and recoatability, and its thermal stability is good, with no yellowing. Setting the measured panel orange-peel grade alongside the gloss reading gives the suitable KMP-4600 scheme.

Advantages of Chemi Tech Leveling Agents

Chemi Tech KMP-4600 series leveling agent is developed for the waterborne systems of coil coating. Its effect in lowering surface tension is pronounced, so the paint flows out fully on a high-speed steel strip and orange peel and roll marks flatten out step by step; its dynamic surface tension is controllable, so the flow-out window still keeps margin once the coil line is sped up; its compatibility is excellent, with no cratering and no effect on intercoat adhesion or recoatability; its influence on gloss is small, so the gloss reading of a colour-coated panel does not swing with the additive dosage; its thermal stability is good, with no decomposition and no yellowing during curing and baking; and the dosage is adjusted flexibly to the paint's solids content, suiting both primer and topcoat.

Industry Pain Points and Solutions

Flow-out problems in coil coating stem mostly from a mismatch between the shear rate of roller transfer and the paint's surface tension, and they end up showing in two places: recurring orange peel and damaged intercoat adhesion.

Roll marks are copied coil after coil along the running direction of the steel strip, and the downgrade decision rises together with the orange-peel grade. The KMP-4600 dosage is set by the roller line speed, and it can effectively press the panel orange-peel grade down.

Craters appear in strings on the topcoat surface, and the continuity of the coating's protection is damaged with it. KMP-4600 has excellent compatibility and does not cause cratering, preserving coating integrity for the corrosion-resistant life of the coil.

The temperature curve of the curing oven directly determines the retained form of the additive. Factoring in the shifts in the paint's solids content and the roller line speed, the dosage range can be mapped out, keeping the panel free of yellowing and gloss loss after baking.

Typical Operating Conditions and Verification

Customer case: a colour-coated panel manufacturer in Jiangsu, for the topcoat roller-coating stage of its building-materials coil coating line.

After the line was revamped for higher speed, the topcoat orange-peel grade rose noticeably, ripples ran in sheets under side-light inspection, and the proportion of downgraded coils climbed with it. Following comparison testing of the panel orange-peel grade and the gloss reading, the plant selected KMP-4600 as the topcoat leveling agent, with the dosage set by the roller line speed. Once in use, the orange-peel grade fell back to the qualified band; the gloss reading stayed stable; the proportion of downgraded coils fell back to the normal level, and repainting man-hours dropped sharply.

Frequently Asked Questions

Once a coil line is sped up and the flow-out window narrows, does the dosage have to be raised in step?

Whether to raise it first comes down to working out just how much the speed-up has amplified the change in shear. KMP-4600 has completed orange-peel and gloss comparison testing across several line-speed bands, and its flow-out behaviour is stable and controllable within the recommended range. The actual dosage takes the paint's solids content and the roller line speed as its baseline, then weighs the curing curve on top of that; Chemi Tech gives the suitable scheme through a parallel comparison of the panel orange-peel grade and the gloss reading.