Treatment of Common Problems of Tinplate Coating (3)

6. Orange peel refers to uneven coating after baking and wrinkles such as orange peel.
1) Dirty back. In the coating applied to the surface of tinplate, the heap is only produced during the process and the back surface is dirty, causing orange peel on the back of the tinplate. This is mainly due to the exclusion of both internal and external materials. Tinplates that are first glazed or coated with silver paint, if the long accumulation time or the baking temperature is not enough, this problem is very likely to occur when other materials are coated on the back side thereof, mainly because of the lubricant component in the light oil and the silver paint. The aluminum composition can easily cause back dirt.
Treatment method: Stacking time is not easy to be too long. If orange peel appears, there is no other way than to wash or rub back.
2) The viscosity of the paint is too high. The viscosity of the coating is too high, and the resin between the macromolecules is very strong. The polymer of the coating resin coated on the tinplate is affected by the cohesive force, and the flow spreading is likely to occur unevenly, resulting in poor spreading of the coating on the surface of the tinplate.
Treatment method: reduce the viscosity of the paint.
3) Improper choice of thinner. Diluting the coating or cleaning the coating machine can result in the high fat of the resin being cohesively formed if the dilute medium cleaning agent is used improperly, weakening the attachment of the resin polymer to the surface of the tinplate, resulting in uneven spreading of the coating.
Treatment method: Use the diluent and cleaning agent provided by the coating supplier correctly. Especially when the colored coating is applied or the type of the coating resin applied before and after the coating is not the same, the coating machine must be cleaned to avoid the coating on the previous process. Under the dirty process coating, the orange peel phenomenon occurs after the film is baked.
7. Eyeholes are also called pinholes. After the coating is dried, there are needle-like holes on the surface. Sometimes there are thin coating films on the small holes, and sometimes they do not even show tinplate. There are several reasons for eye holes.
1) There is a hole in the plastic roller. There are holes in the plastic roller. When the roller is coated, no paint is transferred to the surface of the tinplate to cause eye holes. Generally due to the regularity of the eye holes caused by the plastic roller, the position of the eye holes on the front and rear tinplate is the same and the size is certain.
Treatment method: Replace the plastic roller, or use glue to repair holes.
2) There is oil or dew on the tinplate surface. Since the fine oil or water droplets on the tinplate are incompatible with the coating material, the coating cannot be evenly coated on the surfaces with particulate oil or dew.
Treatment method: use 200 degrees Celsius to bake tinplate; also can reduce coating viscosity, increase the amount of wet coating.
3) Dirty paint and tinplate. Eyes are particularly small.
Treatment method: First, use less stained tinplate to try less, if no problem, then scrub the dirt on the tinplate to solve. Otherwise, change the paint, and pay attention to the correct choice of diluent. In addition, dust on the surface of tinplate is also easy to produce eye holes.
4) The surface of tinplate is electrostatically charged. Tinplate static electricity on the surface also prevents the paint from covering the surface of the tinplate.
Treatment method: Increase the viscosity of the coating, or scrub the conveyor belt to eliminate static electricity.
8. Flying material is similar to printing ink. The speed of the coating machine becomes faster. When the two roller coating layers are divided into two, the drawing wire breaks into several segments, but sometimes there are also many tiny particles floating in the air. Particles scatter due to centrifugal force. Caused the main cloth machine pollution, especially when there is a small amount of air left blank, resulting in dirt, affecting the tank welding. In general, a highly viscous coating tends to be large.
Treatment methods: It is also effective to increase the viscosity or add surfactants, reduce the surface tension, and reduce the coating speed. If it is a white paint, increase the pigment concentration or content. Reducing the thickness of the wet film can also prevent flying material.
9. Zebra stripes appear like mat-like stripes. After the paint has been transferred from the crucible cylinder to the tinplate, the surface of the tinplate cannot be smoothly extended and is in the shape of a mountain, which is mainly due to high viscosity or rapid solvent release. Mixing immiscible paint can also cause this failure.
Treatment method: The coating device must be cleaned. A slow solvent test reduces the viscosity. If the paint becomes too cold in winter or at the end of the vacation, it is also prone to occur. Therefore, the paint should be shaken and the liquid temperature of the paint slightly raised. The surface hardness of the plastic roller is too high, and this phenomenon is also easy to occur. Replace it with a plastic roller with a lower hardness. Sometimes streaks may be caused by insoluble coating in the next process due to paint residue in the coating process on the feed pipe of the coater. In this case, only the paint is replaced.
10. When the climbing temperature is low in winter, a thick coating film is formed around the rapidly heated portion of the furnace (the hot air is blown out). This is because the movement of the molecules in the low-temperature coating is in a slow state and is rapidly at a high temperature. The low-boiling solvent immediately evaporates, and the high-molecular solvent in the resin remains intact and remains in a state where it is not easy to evaporate. If it is further heated, it is melted and agglutinates due to surface tension, and when it is dried in this state, it forms a circular ridge.
Treatment methods: reduce the coating speed, and fully stir the material to raise the liquid temperature, while using the diluent as much as possible to use high boiling point, surface tension and the coating surface tension close to the solvent.
11. When the phantom baking is performed, the shape of the tint on the surface of tinplate becomes pale. Because the hot air is absorbed by the flower iron frame, the baking of this part is insufficient, the solvent evaporates slowly, and the surface tension pulls, the coating film becomes thinner and the color becomes lighter. The smaller the amount of film, the more likely this phenomenon occurs. The viscosity of the paint is too low and it is prone to this failure. This phenomenon is particularly noticeable especially when winter is high.
Treatment method: generally can reduce the coating speed to extend the preheating time, while reducing the amount of coating under the conditions allowed by the process. Also pay attention to the use of fast evaporation diluent and the viscosity should not be too low.
12. The coating on the tinplate of the flower tinplate was in contact with the front iron frame during the undying period, resulting in traces of flower iron frames.
Treatment method: If tinplate deformation caused by tinplate bending, tinplate should be replaced. Otherwise, you should check if the hot air is too strong, whether the tinplate jumps on the flower iron frame, or the flower iron frame... (To be continued)