Treatment of Common Problems of Tinplate Coating (1)

The printing principle of tinplate is basically similar to that of lithographic offset printing, except that the printing object of tinplate is non-adsorptive low-carbon tin-plated steel sheet. Before printing, one layer of film must be laid on the surface of the tinplate. Its main function is to firmly attach to the surface of the tinplate, and at the same time, it can adhere to and adhere to the ink printed on the surface of the tinplate. For a specially qualified printed tinplate product, a layer of internal paint is also applied on the back to protect the quality of its contents. At the same time, it is necessary to ensure that the tinplate print has certain mechanical processing performance and use value when it is transferred to the next process.
At present, there are many magazines on the quality of tinplate lithography has been introduced, this article is no longer involved. The following mainly describes the common quality problems and treatment methods of tinplate coating process.
First, the treatment of the appearance quality of tinplate 1. Coated uneven coating on the surface of the tinplate is not the same as the thickness of the coating. If it is dried at the same temperature and speed, it is prone to insufficient hardening of the coating film thickness and excessive hardening of the coating film thin part, resulting in the adhesion of the coating film. Stain, hardness, corrosion resistance, bending resistance, impact resistance, etc., for the colored coating will see the film color shades. The following factors affect the coating unevenness.
1) The gap between the rollers and the rollers is different at both ends. The gap between the plastic roller and the pressure coating roller, the transfer roller and the plastic roller, the transfer roller and the transfer roller, and the feed roller and the transfer roller are inconsistent when adjusting the gap between the roller and the roller. This often results in the feed of tinplate. The thickness of the coating varies from one direction to the next.
Treatment method: When the thickness of the coating film is not uniform, check the gap between the feed roller and the transfer roller with a plug gauge first, and then check whether the gap between the two ends of the feed roller and the transfer roller is the same. When they are parallel to each other, adjust the gap between the cross roller and the applicator roller, the optical head, and the plastic roller so that the three rollers and the two rollers are parallel to each other.
2) The viscosity of the paint is too large. The viscosity of the coating is too viscous, and the cohesion between the resin and polymer is large. When the cohesion is greater than the adhesion of the resin on the surface of the tinplate, the coating on the tinplate cannot be uniformly spread, and the higher the rotation speed of the coating machine, the more likely it is to cause tinplate. Random surface irregular coating.
Treatment methods: appropriate to reduce the viscosity of the coating, or the surface of Zhang Guoxiao solvent for thin, the purpose of the spring is to reduce the cohesion between the resin polymer, so that the coating on the surface of the tinplate to spread evenly, and slow down the coating speed. Sufficient time to spread evenly on the surface of the tinplate.
3) The surface oil content of tinplate is high. The oil film on the tinplate surface is mainly to protect the tinplate from oxidation corrosion before coating. The thicker the oil film, the poorer the wettability of the coating resin polymer on the tinplate surface, the tincture material cannot uniformly adhere to the surface of the tinplate.
Treatment method: When the oil content of tinplate is high, the viscosity of the coating can be appropriately reduced. For tinplates with too high oil content, degreasing is done only by baking at high temperatures.
4) The quality of the paint is not good. The paint mixed with impurities or stored for too long and layered, resulting in the coating before the coating part of the resin polymer has occurred polymerization reaction. Although the coating was sufficiently shaken before coating, the polymerized polymer bonds could not be stirred off, and there was a tendency for the patch to appear uneven when applied.
Treatment method: change the paint.
5) The choice of diluent is not correct. The thinner causes the resin and the diluent to be insoluble, the paint separates and precipitates, and after the baking, the coating film lines tend to appear, and the flow development is not good.
Treatment method: The correct choice of diluent, it is best to use the matching solvent provided by the paint supplier.
6) The plastic roller is not concentric. After the eccentric adhesive coating drum is loaded with a coating machine, the surface circumferentially different position is different from the contact pressure between the tinplate and the pressure coating roller, resulting in less coating thickness on the surface of the tinplate. one. Colored paints appear to have a color gradient from light to dark or from dark to light.
Treatment method: Refinish the plastic roller.
2. Dirty 1) The back of the blade caused by the abrasion of the blade. After the tinplate surface was coated with a roller coating, a small amount of regular line-shaped paint was stained on the back side, mainly because the sand particles in the coating caused the defect of the knife, and the coating on the pressure coating roller was not scraped off by the scraper.
Treatment method: Re-grind the scraper to solve. It is worth mentioning that because of the defects of the grinding wheel, the blade that appears to be very smooth has fine burrs or gaps. So, just dressed...
2) Back dirt caused by the conveying device. The coated tinplate surface is in contact with the conveyor belt and is likely to cause slight peeling off of the film. It is continuously accumulated by the belt. When other tinplate products are coated, the algae that accumulates on the belt is easily exposed to the tinplate. Adsorption on the back forms a trail of the back of the belt. In addition, the viscosity of the coating is too thin, and the adhesion on the rollers and rollers is small. When the coating machine runs at a high speed, the paint splashes easily, causing irregular back stains on the back of the tinplate.
Treatment method: wipe clean the delivery device. If the paint is splashed and the back is dirty, follow the flying material troubleshooting.
3) The back of the adhesive sheet is dirty. When the baking temperature is insufficient or the outlet of the rice is not cooled sufficiently, when the tinplate is accumulated at a high temperature, the tinplate and the tinplate will stick together, causing the coating film coated on the tinplate surface to be adsorbed on the back of the tinplate laminated thereon to form a back dirt. Generally speaking, the surface temperature of tinplate after cooling is at most 10 degrees Celsius higher than room temperature. If the cooling is improper, the coating film will not be completely hardened.
Treatment method: Appropriately increase the baking temperature so that the coating on the tinplate can be fully polymerized. Increase the amount of cooling air to harden the coating. Sometimes reducing the coating speed can also prevent sticky stains. (To be continued)