Because the printing ink of packaging bag is dried by solvent volatilization, there is a certain amount of residual solvent. The odor and toxicity of organic solvents will pollute food and endanger human health. Beverage bag manufacturers introduced that the current national standard is less than 10 mg per square meter. Therefore, the residual solvent in printed matter is an important indicator for the inspection of ink quality and packaging bag printing quality. How to control the residual solvent is discussed.
1、 Thin film
After the mixed organic solvents were coated on the film by printing machine, the order of residual amount was MST > km > Kop > OPP > CPP > Pt > Pet > NY.
If selected, the easily produced residual solvents are listed as follows: ① CPP, toluene ② OPP, toluene ③ pet, toluene ethyl acetate ④ NY, isopropanol, toluene ⑤ km, methyl ethyl ketone (MST), isopropanol, toluene (7) Pt, isopropanol, toluene (8) Kop and toluene. For the film with the permeability of a certain solvent, the residual amount is more because of its affinity with the solvent. The residual amount of the film with low permeability is also small.
2、 Printing press
(1) If the wind speed in the dryer is large enough, the residual amount of solvent will be inversely proportional to the rise of temperature. If the air speed is not enough, the dependence of solvent residue on temperature will disappear. From this result, we can know that the efficiency of ink film on heat conduction is about the residual tendency of solvent.
(2) If the amount of ink transferred to the film before entering the dryer, due to certain conditions and into a semi dry state. For example, the distance between the printing film and the dryer is too long, or the printing speed is too slow, or a large amount of air in the dryer leaks out and touches the printing surface, and uses abnormal drying method to dry the printed matter, or in the dryer, the influence of wind speed is less and the drying depends on temperature. On the contrary, the residual volume ratio may increase. This abnormal case, commonly known as "crust", means that the dry film on the surface of the ink hinders the diffusion of solvent vapor, and the whole film is not evenly dried. In this case, the diffusion of solvent vapor must have a large energy, but there is a limit to this energy due to the shrinkage, wrinkle and relaxation of the film itself.
3、 Solvent use
Because of solvent volatilization in gravure printing process. In order to make the ink to maintain a certain viscosity, must often add solvent. In order to control the solubility of ink and drying speed. Beverage bag manufacturers introduced that solvents are generally not used alone, most of them are mixed by several solvents. The solvent for dilution is set according to the different types of ink, considering the reconstitution of ink, the stability of long-term printing on the printing machine, the stability of residual ink, the balance between the first level of mixing with new ink, and the solvent residue of printing products. Therefore, it is dangerous to use other statistics instead of the set solvent.
In order to consider the high-speed printing of gravure, the ink requires fast drying and solvent residue after printing, so gravure ink can only use solvent with low boiling point and fast evaporation speed. http://www.ycritai.cn/
Dongguan Beite packaging materials Co., Ltd
Aluminum foil packaging bags, mask bags, self-supporting zipper bags, eight side sealing bags, red wine bags, dog food bags, beverage bags, bags in boxes, wrapped films, perforated fruit bags.