Ink is an indispensable material in the decoration and packaging of printed goods. Through printing, the packaging surface becomes beautiful, colorful, and attractive. In recent years, with the rapid development of the printing industry, various plastics and paper packaging and printing have been continuously improved, and the requirements for product packaging are getting higher and higher. The printing of composite flexible packaging is different from the printing of general packaging, that is, the former is the inner printing, and the latter is the surface printing. The ink used by the two is called the inner printing ink and the surface printing ink. We must analyze these two before printing. The difference in inks makes a lot of sense to use them correctly.
Most of the inks in China are composed of 20% to 40% binder, 5% to 15% pigments, 40% to 60% organic solvents and 0% to 5% additives. The linking material is the adhesive resin and the key component of the ink. It binds the pigment and the material to be printed together to provide adhesion and make the ink shiny. Pigment determines the type of color. The solvent dissolves the resin, adjusts the viscosity, adjusts the drying speed, and improves the wetting effect on the printing material. Additives play a role in improving viscosity, weather resistance, aging resistance, and increasing gloss. The following is a brief analysis of our factory after years of summary analysis of the differences between printing inks and surface printing inks.
1. The difference between link materials
The bonding material of surface printing ink is mainly polyamide resin, which has good adhesion and good gloss, but it is not suitable for high temperature conditions and has poor fastness during compounding. The bonding material of non-cooking type printing ink is mainly chlorinated polypropylene, foreign Also useful are nitrocellulose and vinyl chloride-vinyl acetate copolymer resin. Domestic Golden Dragon GD-1 and Oriental 200 belong to this category. The high-temperature retort oil-linking material is polyurethane. When used, a certain amount of hardener is added, the two liquids are mixed, and the reaction crosslinks.
2. Differences in solvents used
The solvents used for surface printing inks are mainly xylene and isopropyl alcohol. In general, the printing ink solvent is mainly toluene and ethyl acetate. The high-temperature cooking lining printing ink is mainly based on ethyl ketone and ethyl acetate. Liyin ink solvent is suitable for high-speed printing, the volatility of the solvent is fast, and the residual amount of the solvent is particularly small.
3. Difference in wear resistance
Because the polyamide resin has good flexibility and greater elasticity, the added additives make its wear resistance better and improve, and it is more firm against external objects. The chlorinated polypropylene resin of Liyin ink resin has particularly good rigidity and poor abrasion resistance. Since it is Liyin, the requirements for abrasion resistance are correspondingly lower.
4. The difference between different accessories
The surface printing ink and the inside printing ink are different due to the connection and other accessories, additives and additives. The surface printing ink is often added with dehydrated apple and kiwi fruit acid ester to improve adhesion, increase gloss and increase viscosity. Liyin ink is also added with various pigment dispersants, enhancers, defoamers and other additives.
5. The difference in printing process
The process of printing on the inside is exactly the same as that of the general process, but the image on the printing plate is the reverse image when the plate is printed, and the image is the positive image after printing. The printing speed of surface printing ink is slow, and the printing speed of internal printing ink is faster than that of surface printing. The printing color sequence is also different.
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