The commonly used varnishes are solvent-based, water-based and UV varnish. Solvent-based solvents have certain restrictions on the environment due to their volatile solvents.
Water-based varnish is an environmentally-friendly varnish that has become more and more widely used in recent years. It has high gloss, fast drying and good film formation properties, and excellent friction resistance. It is a very ideal varnish. However, 30% of the drying process of water-based varnish is through volatilization, and 70% is absorbed and absorbed by the material, but tinplate is not absorbent at all, so it is currently not suitable for use in tinplate printing.
UV varnish is mainly composed of photosensitive resin, reactive diluent, photoinitiator and auxiliary ingredients. UV curing is a film that is cured by initiating a polymerization reaction under ultraviolet irradiation. As the tinplate surface is a non-absorbent surface, post-printing drying is one of the main technical problems of tinplate printing. It adopts ultraviolet irradiation for instant drying, fast curing speed, strong film surface after drying, good gloss, abrasion resistance and protection, and does not pollute the environment. It is a widely used varnish in recent years. UV varnishes still have high cost, large energy consumption and irritating odor.
Various varnishes have advantages and disadvantages. In actual production, the correct type of varnish should be selected according to the characteristics and uses of the printed product. However, no matter what type of varnish is used, you should know the solid content, purity of the oil, coating viscosity, baking temperature and other technical data before use to ensure the hardness (wear resistance) and gloss of the coating film. Degree and adhesion.