First, the technical requirements of polishing oil
In addition to having a colorless, odorless, strong gloss, rapid drying, and chemical resistance, the ideal coating oil must also have the following properties.
1, film transparency, no discoloration
Decorative prints to obtain excellent glazing effect depends on the formation of a colorless, transparent film on the surface of the printed sheet, and the graphic does not change color after drying. And it should not be discolored or yellowed due to sun exposure or long use.
2, the film has a certain degree of wear resistance
Some glossy prints require some abrasion resistance and scratch resistance after polishing. Because of the assembly line production processes such as high-speed box-making machines, cardboard boxes and packaging machines, and book covers, the surface of prints is subject to friction and must therefore have wear resistance.
3, have a certain degree of flexibility
The glossy film formed on the surface of any type of varnish must maintain good elasticity so that it can adapt to the flexibility of paper or paperboard, and it will not be damaged or cracked or peeled off.
4, film resistance to environmental performance is better
After glazing, some of the printed matter is used to make all kinds of packaging cartons. In order to be able to protect the products being packaged, the glazing film layer must have good environmental resistance. For example: The packaging of food, cigarettes, cosmetics, clothing and other commodities must have moisture-proof and mildew-proof properties. In addition, the chemical properties of the dried film must be stable. Do not change the performance due to contact with a weak acid or weak base or other chemical substance in the environment.
5, has a certain adhesion to the surface of the print
Due to the integral density value of surface ink layers, the printability of the printed matter is greatly reduced. In order to prevent the dry and cracked film from drying after use, it is required that the film has strong adhesion, and the ink and ink transfer are used in various types. Accessories have a certain degree of adhesion.
6, good leveling, smooth membrane surface
There are various types of materials for printing materials, and the effects of printed graphics, such as the surface absorptivity, smoothness, and wettability, are very different. In order to make the coating on the surface of different products can form a smooth film layer, it requires coating oil. Leveling is good, film surface is smooth after film formation.
7, post-printing processing flexibility
After the glazing of prints, it is generally required to go through the post-process processing, such as: molding processing, stamping and electro-aluminum processing. therefore. It is required that the post-printing processing of the coating film should be wide enough. For example, the heat resistance is better. After the electro-aluminization is stamped, no sticking phenomenon can occur; the solvent resistance is high, and the dried film cannot be blisters, wrinkles, and hair due to the influence of the adhesive in the post-processing. Viscosity phenomenon.
Second, the choice of polishing oil
The choice of glazing oil must meet the basic principles of science, economy and practicality.
The so-called science refers to the need to study whether Varnish meets the physical and chemical properties of the glazing and use of printed materials. For example, the covers and seals of books, catalogs, and albums require that glazing oil not only has high transparency, but also has better abrasion resistance and folding resistance; food packaging varnish must first be non-toxic and have certain moisture-proof and anti-corrosion properties; The packaging paper carton is varnished and requires high chemical stability. It cannot be discolored or yellow due to placement (sunlight or light), or sticking and other phenomena occur due to stacking.
2. Economy
Refers to the choice of varnishes, must be glazing oil commensurate with the print, to avoid the use of high-grade glazing processing medium and low-grade print. For example, for high-grade printed products, you can use solvent-based coating with high cost, good quality calendering, UV-curing, or acrylic resin as the main agent; on the contrary, if the printed matter is a bulk product such as textbooks, It is advisable to use a general solvent type coating oil whose quality is moderate and whose quality can meet the processing requirements.
3, practical
It refers to the choice of coating oil to match with the coating equipment. For example, solvent-based coating oils are only suitable for ordinary coating machines; UV-curable coating oils must be used on machines equipped with an ultraviolet drying device; alcohol-soluble or water-soluble coating oils must be satisfactorily applied to the coating machine. Varnish drying requirements (generally require a drying path length of more than 6m, temperature above 65 °C). In addition, we must also consider the need to save labor and materials, but also suitable for mechanical mass production, try to reduce production costs, less investment, more output. The choice of coating oil must also pay attention to safety, hygiene and environmental protection requirements. From the perspective of safety, we should use varnishes with good storage properties and non-flammable properties. We should use odorless, non-toxic and odorless varnishes in consideration of hygiene and environmental protection. The production site and the ventilation conditions of the machine are good, and the selection range may be appropriately wider. On the contrary, the coating oil with aromatic substances as the solvent should not be used to prevent the operator's physical health and environmental pollution.
