Metal coils stacked in rows alongside processing equipment

Speed the coil line up and the coating film enters the oven before it has spread, the panel carries orange peel, gloss drops away, and as soon as a colour difference claim is raised the whole coil is scrapped — the output gained from the speed increase does not come close to covering the loss.

Chemi Tech makes leveling agents for coil coating and industrial coating systems, drawn from the leveling agent KMP-4600 series. How a grade is matched depends on the resin system, the film thickness and the oven temperature curve. KMP-4600 is a waterborne system with a marked reduction in surface tension, and it holds dynamic surface tension down as well, so the film spreads when the line speeds up; where intercoat adhesion has to be held, the addition level has to be calibrated against line speed. Chemi Tech works from the resin system and the line speed data to settle the addition level and the point of addition, and recommends the best fit.

Advantages of Chemi Tech Leveling Agents

Chemi Tech leveling agent KMP-4600 series cuts surface tension markedly, so the film spreads properly before it enters the oven and orange peel moves up a grade. Dynamic surface tension is held down as well, so it still spreads when the line speeds up, with no pull-back at the edges. Its effect on gloss is small: clearcoat systems stay clear once it is in, and pigmented coats show no haze. Heat stability holds up as well, with no decomposition and no yellowing through the oven stage. And recoatability is left room for, so the coats hold together on a rework touch-up.

Industry Pain Points and Solutions

Orange peel on a coil surface is usually not a matter of too little leveling agent; it is the leveling window squeezed out by the speed increase. What worries people most is a whole coil going to rework, burning material and time.

Looking only at the addition level and not at line speed is the first difficulty encountered. The moment orange peel appears more leveling agent goes in, and in the end adhesion falls away and the problem gets more complicated. Chemi Tech measures the static and dynamic surface tension of the system together and looks at which stretch the gap falls in.

What follows is an oven curve that has not kept pace. When the oven heats too sharply the film sets before it can spread, so the texture naturally cannot be pressed flat. Chemi Tech's approach is to verify the leveling time and the oven ramp curve together, rather than looking only at how much additive went in.

Another pain point is that once line speed is adjusted the old parameters are void. When the line speeds up the rollers turn faster and the film gets thinner, so there is less room to level. Chemi Tech's approach is to run a leveling comparison against the actual line speed and recalibrate the addition level and the point of addition, so whole coils do not have to be sacrificed to the trial.

Typical Conditions and Verification

Customer: a coil coatings enterprise in Guangdong, applying it to the topcoat line for metal coil.

Once this plant speeded up its coil line the panel carried heavy orange peel, gloss dropped a grade, the colour difference would not hold, and the proportion of whole coils going to rework was climbing. The solution offered by Chemi Tech leveling agent was: against the resin system and the line speed, a suitable grade was selected from the KMP-4600 series, the addition level and the point of addition were recalibrated against line speed, and the oven ramp curve was adjusted to suit. After the change the orange peel on the panel moved up a grade and gloss came back inside the specification.

Frequently Asked Questions

Will too much leveling agent pull intercoat adhesion down?

It will: if the surface tension is pressed too low, the two coats will not hold together on a recoat. The KMP-4600 series Chemi Tech supplies to coil plants has been compared against recoatability, and at normal addition levels the adhesion data is stable. If there are further questions, the research department at Chemi Tech will answer them for you at any time.