The difference between top printing ink and inside

The difference between surface printing ink and internal printing ink

ink is an indispensable material for the decoration and packaging of printed goods. Through printing, the packaging surface becomes beautiful, colorful, exquisite and attractive. In recent years, with the rapid development of the printing industry, the packaging and printing of various plastics and paper industries have been continuously improved, and the requirements for the quality of product packaging have become higher and higher. The printing of composite flexible packaging is different from that of general packaging, that is, the former is internal printing and the latter is surface printing. The inks used by the two are called internal printing ink and surface printing ink respectively. We must analyze the differences between the two inks before printing, and it is of great significance to use them correctly

most inks in China are composed of 20% - 40% binders, 5% - 15% pigments, 40% - 60% organic solvents and 0% additives, namely HRA, HRB, HRC ~ 5%. During the production of binder, it is a bonding resin, which is a chain component of ink. It binds the pigment and the printed material together, plays an adhesion role, and makes the ink shiny. Pigments determine the type of color. The solvent dissolves the resin, adjusts the viscosity, adjusts the drying speed, and improves the wetting effect on printing materials. Additives can improve viscosity, weather resistance, aging resistance and gloss. The following is a brief analysis of the differences between inner printing ink and surface printing ink summarized by our factory for many years

1. The difference of binder

the binder of surface printing ink is mainly polyamide resin, which has good adhesion and gloss, but does not adapt to high temperature conditions, and has poor fastness when compounding. The binder of non cooking internal printing ink is mainly chlorinated polypropylene, and nitrate fiber and vinyl chloride vinyl acetate copolymer resin are also used abroad. Domestic Jinlong GD1 and Dongfang 200 belong to this category. The binder of printing oil quantity for high-temperature cooking is polyurethane, which makes the resilience LS PVC material have good flame retardancy, high transparency, high reflectance and uniform metal color effect. When used, add a certain amount of hardener, mix the two liquids, and react and crosslink, such as Dongfang 300

2. difference of solvents used

the solvents used in surface printing inks are mainly xylene and isopropanol. 1. The functional characteristics of the drop weight impact tester: generally, toluene and ethyl acetate are the main solvents for printing ink. Heat resistant cooking inks are mainly ethyl ketone and ethyl acetate. The inner printing ink solvent is suitable for high-speed printing, the volatility of the solvent is fast, and the solvent residue is particularly small

3. Difference in wear resistance

due to the good softness and great elasticity of polyamide resin, the addition of additives improves its wear resistance, and it is relatively firm in contact with external objects. The inner printing ink resin chlorinated polypropylene resin is particularly rigid and has poor wear resistance. Due to the inner printing, the requirements for wear resistance are correspondingly lower

4. Differences of auxiliary materials

due to the different connection between surface printing ink and internal printing ink, the auxiliary materials, additives and additives are also different. Dehydrated apples and kiwi fruit acid esters are often added to surface printing ink to improve adhesion, gloss and viscosity. Printing ink also adds various pigment dispersants, enhancers, defoamers and other additives

5. The difference of printing process

the plate making process of inner printing is exactly the same as that of general plate making process, but the image on the plate during surface printing is reverse image, and it is positive image after printing, and the image and text of inner printing plate is positive image, and it is reverse image after printing. The printing speed of surface printing ink is slow, and the printing speed of inner printing ink is faster than that of surface printing. The printing color sequence is also different