Analysis of the printing ink failure of the hottes

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Trouble analysis of newspaper printing ink

getting dirty

in the process of printing, getting dirty and sticking dirty are two different concepts. Getting dirty generally refers to dirt in non graphic areas, including blurred imprints, dots, etc. Dirt can be divided into floating dirt and oil dirt

15. Total spring stiffness: 300 ± 10kgf/cm Floating dirt

floating dirt refers to the light color dirt in the non graphic area or the blurred image and text in the graphic area, and the dirt is relatively easy to wipe off

1) causes

① due to the soft ink and weak water resistance, some inks will emulsify after being affected by the fountain solution and enter the fountain solution through the circulation system to form an oil in water lotion; ② The chemicals and wetting agents in the paper contribute to the emulsification of ink; ③ Some fountain solutions contain substances such as soaps or detergents, which will also cause ink emulsification

2) solutions

① change to ink with slightly higher viscosity, good water resistance and difficult emulsification; Or add high viscosity inking oil to the original ink; ② Replace the paper used; ③ Adjust the amount of fountain solution to ensure proper conductivity and pH value

2. Oil dirt

oil dirt is that the non graphic area of the fingerprint plate has grease sensitivity, causing the blank area of the printing plate to be inked and contaminating the printed matter

1) causes

① the ink is too thin and soft; ② Ink is given for a long time during printing, and the amount of ink is too large; ③ There are high concentrations of free fatty acids and surfactants in the ink; ④ The influence of treatment agents in pigments; ⑤ The surface structure of the printing plate is damaged by the excessive pressure of the printing plate ink cots and the blanket or the aging of the printing plate cots and the blanket; ⑥ Dissolve fat sensitive substances from paper coatings

2) solutions

① replace the ink or add high viscosity resin oil to the original ink to make the ink have better viscoelasticity; ② Control the ink supply during printing; ③ Control the amount of fountain solution; ④ Adjust the pressure of cots and blanket, or replace cots and blanket; ⑤ Replace the paper

no inking

1 Causes

during the printing process, sometimes the printing plate does not get inked. The reasons for this phenomenon are as follows

① the ink viscosity is insufficient, the fluidity is small, and the yield value is too large; ② The proportion of solid components in the ink is too large, so that the ink lacks leveling, the ink is "stunned", and the ink filament becomes shorter; ③ The pigment in the ink agglomerates again and causes gelation; ④ Ink water or ink is sensitive to water and has poor water resistance, which accelerates the emulsification of ink; ⑤ The ink roller rubber surface or blanket is aging and hard, and the printing plate is worn

2. Solution

① for inks with short ink filaments, alkyd resin or other materials with good fluidity and large gap between self-control and control can be added, and the inkability can be readjusted through a three roller machine; ② Use resin binders with good solubility to wet the pigments, such as solving the flexible packaging problems of medical devices and drugs, bottle caps, sealing parts and primary experimental supplies, so that the pigments can be evenly dispersed to prevent their re aggregation; ③ Use ink with good fluidity and strong water resistance. Black ink try not to use rubber to adjust the blackness, because the rubber content is more, it is not easy to make the ink show better fluidity; ④ Adjust the rubber roller pressure or replace it with a new rubber roller and blanket

surface crusting

in the printing process, when adding new ink, sometimes you will find that there are different degrees of film on the ink surface around the ink bucket. If these film is added to the ink bucket, it will seriously affect the ink supply performance of the machine

close the oil delivery valve 1 Cause

the binder in offset printing ink is composed of synthetic resin, vegetable oil and high boiling mineral oil. At present, flaxseed oil, which is widely used in offset printing rotary ink, is dry oil. Because this kind of oil contains more unsaturated fatty acid groups, it can evenly absorb oxygen in the air, oxidize and polymerize into a tough solid film, so offset printing rotary ink has good dryness in the air. At the same time, due to the use of some inorganic pigments (such as iron blue) in the ink formula, the ink is prone to surface scaling during storage

2. Solution

some anti drying agents (anti scaling agents) can be added in the ink production process. Because most of them are strong reducing agents and can be oxidized preferentially, they can delay the oxidative polymerization of dry oil. In addition, the ink should be avoided to be exposed to the air for a long time

the above are common failures of newspaper printing ink in production. In the printing process, no matter what faults you encounter, you should carefully observe them, systematically analyze them in combination with the appearance, and then find out the solutions to the problems. For the problems that cannot be solved at the moment, you can eliminate them one by one, and finally solve the problems completely

source: Printing Technology

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