PVC is polyvinyl chloride sheet, which is a kind of strong polar polymer compound formed by polymerization of vinyl chloride monomer under certain conditions. It has good toughness, low surface hardness, easy to mark and leave traces. It is widely used at present. Produce generous and beautiful nameplates and signs for various instruments, meters, and household appliances.

Signage is generally printed using manual screen printing. For a small area (within 800500mm) of PVC mask, the author uses the normal process, first screen printing after the text, and then screen printing background. The screen printing background color has certain limitations. It is constrained by the size of the scraper and the size of the frame. The largest net distance is only 100700mm. If this size is exceeded, the background color cannot be overprinted. The background color of the PVC mask requires the ink to be uniform and complete, and there must be no joint marks. Therefore, we cannot undertake large-scale PVC mask processing business. In order to survive in the competition and seek development in technology, we have made improvements in the process to meet market demand.

The inkjet printing technology of the car has inspired us. Can we use the undercoat instead of the screen overprint? We have carried out many spraying experiments with this problem. We found that the undercoating can completely achieve the effect of screen printing, and the end of the mask is ejected. The color ink is more uniform than the screen printing. We use the PQ-1 spray gun and the O-8KPa air compressor for the spraying background. The production process is very simple.

The improvement of this process has brought vitality to the company I work for. We soon took over a big business and made a PVC mask for a large-scale equipment for a plastic window equipment factory. The mask requires a size of 1500900mm. Due to the improvement of the process, we no longer worry about the underlying problem. Pictures of large-area PVC masks can be partially screen printed, as long as each screen printing has a registration mark, and several screen printings can be used to print graphics that meet the dimensional requirements. The background color we use the spraying process, the coating background color ink has strong hiding power, the dark color ink layer can't bleed each other, the fastness is better, it can't crack. General use of domestic PVC special ink or imported 7000 series, this ink has a good adhesion on the surface of PVC. Use imported 783 slow-drying solvent to adjust the ink, the viscosity of the transferred ink is smaller than that of screen printing, and it is suitable to spray mist. If there is a special requirement in the PVC mask, use a tape to cover the special part. After spraying the background, dry it, and then gently remove the tape. Before spraying, the PVC mask needs to be placed horizontally on the table and sealed with tape around. When spraying, the air compressor pressure generally needs 3-4KPa; the spray gun is between 30-40cm from the mask. Since the squeegee angle is 20-70 degrees in the plane printing, the spray gun and the mask also have this angle. The first pass should be uniform and rapid when spraying, and the ink cannot be sprayed too thick. After spraying the first pass, fast drying with a chain dryer, the temperature can not exceed 60 degrees, PVC working temperature greater than 60 degrees will be deformed. Fast drying is to prevent 783 solvents from corroding PVC, because the concentration of 783 in spraying ink is larger than that of silk screen printing. After the first drying, it was cooled to room temperature and sprayed a second time. The second time it sprays on the PVC mask, it looks flat and even in color, and it is quickly dried and cooled.

Source: Print World
Author: Chen Minghua