3. Ink type
The use of water-soluble solvent, water-soluble ink type. The benzene containing ink (mainly chlorinated polypropylene resin and aromatic polyurethane resin) mainly depends on the solvent release of the ink resin. The better the solubility of the solvent to the resin, the greater the affinity between the resin and the solvent, the poorer the release property, and the higher the residual solvent. The release of toluene and xylene of chlorinated polypropylene resin ink is worse than that of aromatic hydrocarbon polyurethane resin ink.
4. Printing press
The influence of printing press mainly includes the following aspects:
A. The length of the bellows B, whether the air volume is sufficient, C, the angle of the air box blowing nozzle D, the air pressure e, the distance between the nozzle outlet and the film F, whether there is a terminal drying equipment g, the direction of the air duct
This article focuses on the terminal drying equipment. The printing machine of our company is an early model, without terminal drying equipment, the residual solvent has been large. Later, we contacted the printing machine manufacturer and installed a group of terminal drying equipment on the top of the eight color printing machine and two sets of terminal drying equipment on the top of the twelve color printing machine. The effect is very obvious after use.
The data of solvent residue are as follows: unit: mg / m2
Printing unit
12 colors (with full plate ink)
8 colors (without white ink)
Terminal drying not used
Toluene 4.23, ethyl 2.25
Toluene 3.25, ethyl ester 1.26
After the terminal is dried
Toluene 2.51 ethyl ester 1.47
Toluene 1.98, ethyl 0.98
5. The influence of printing solvent
Ink itself contains a large number of solvents, while printing will add toluene, xylene, butanone, ethyl acetate and other large amount of mixed solvents. The boiling point of isopropanol, ethyl acetate, butanone, toluene and xylene are 82.5 degrees, 77.1 degrees, 79.6 degrees, 110.6 degrees and 135-140 degrees, respectively, of isopropanol, ethyl acetate, butanone and xylene, respectively. The boiling point of xylene is high and difficult to volatilize, so it should not be used or used less. Even though butanone is easy to volatilize, its residue is very low, but it has a strong smell, so it should be used less as far as possible. Do not use coking toluene.
6. Printing technology
Because most of the packaging structure is the packaging manufacturers can not choose, and the price of benzene free ink is much higher than that of benzene containing ink, so how to reduce the solvent residue of benzene containing ink is a problem we have to work hard to solve in production.
A. Due to the small amount of butanone and xylene in printing, it is easy to control if it can be used less or not.
B. The temperature of the oven should be increased step by step. The temperature of the latter oven should be 3-5 degrees higher than that of the previous one. Generally, the temperature of ink and white ink should be set at 65-75 degrees.
C. The inlet air volume and exhaust air volume should be basically balanced, and the exhaust air volume should be slightly greater than the inlet air volume to avoid hot air escaping.
D. The printing speed should be properly controlled so as to have sufficient drying time.
E. After printing, the film should be emptied through 1-2 printing units, so as to further volatilize the solvent.
F. The humidity of the workshop should be controlled between 50% and 70%, which should not be too high. If the humidity is too high, it is not conducive to the solvent volatilization. If the humidity is doubled, the drying speed of the ink will be delayed nearly twice.
G. On the premise of not affecting the printing quality, the air blowing can be increased to accelerate the solvent volatilization.
H. Control the purity of the solvent. If the purity of the solvent is not high and contains many components with high boiling point, the solvent with strong volatility will come out first, and the weak one will remain. The volatility of solvent will gradually decrease and the residual amount of solvent will be relatively high.
1. The ventilation of the workshop is good, especially in the workshop with good sealing performance (such as GMP workshop), the inlet air volume and exhaust air volume must be balanced, otherwise it is easy to cause a lot of residual solvents in the air of the workshop, and the smell is very strong.
J. The winding tension should not be too large. It is easy to have slight deformation by hand pressing. The winding diameter should not be too large, generally no more than 500mm.
K. The air blowing in the oven should be directly or slightly upward aligned with the printing film, and a baffle should be added at the bottom of the oven to prevent the hot air from escaping.
50. For example, some printing machines with a width of 1000 mm can print 1050 mm or even 1070 mm film, but the residual solvent is much higher than that of 1000 mm film.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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