Why do some boxes that are not laminated need to be varnished?
Varnish is through the coating, spraying or printing methods, in the printed surface attached to a layer of colourless transparent coating, after levelling, drying, and calendering, in the printed surface to form a thin and uniform layer of gloss.
It not only increases the gloss of the surface of the printed matter but also improves its stiffness. At the same time, after varnishing the printed matter waste can be recycled or self-decomposition does not pollute the environment.
Therefore, varnishing is a process with great development potential, and may gradually occupy the plastic laminating process market.
There are many types of varnish, but their material composition is basically the same. Mainly by the main agent (film-forming resin), additives and solvents.
The quality of the main agent determines the quality of the coating film and the physicochemical properties of the varnish, such as gloss, folding resistance, and suitability for post-processing.
Additives are added to improve the physicochemical properties and processing characteristics of the varnish. For example, curing agents are added to improve the film-forming properties of the main agent resin and increase the bonding strength of the film layer. Surfactants are added to reduce the surface tension of the varnish and improve its levelling. There are also defoamers, plasticisers and so on. The dosage of all kinds of additives is generally not more than 5% of the total amount.
The main role of solvent is to disperse and dissolve the main agent and auxiliary. Varnish oil has high requirements for solubility, volatility and other indicators of solvents. Varnish oil toxicity, odour, dryness, levelling and other physical and chemical properties are directly related to the choice of solvent.
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