Ink Printing Common Failure Analysis - Deinking

5. Deinking

Phenomenon and reason: Deinking means that the ink does not rotate with the ink fountain in the ink fountain, but separates from the ink fountain shaft, so that the ink string roller and the uniform ink roller do not ink. After deinking, it will affect the normal ink transfer roller, so that the printing plate can not get the desired ink and fade, resulting in different shades of ink.

Common deinking has the following reasons:

1) Insufficient oiliness and low viscosity of the ink, the ink bu moves with the rotation of the ink fountain shaft, causing deinking.
2) The ink has poor fluidity and does not easily flow between the ink cutter shaft and the blade, affecting the ink and causing deinking.
3) The state of gelation or gelation of the ink causes the viscosity and fluidity to decrease and the printing performance to be lost, while static ink droplets are causing deinking.
4) The ink contains too little oil, too much silt, and does not transfer pigment particles well and stays in the ink fountain to form deinking.
5) The ink dries too fast, which causes the ink fountain shaft to dry and solidify, loses the ink transfer performance, and blocks the gap between the ink fountain roller and the blade to form a deinking.
6) Ink contains too many impurities such as ink, residue, and the like, which blocks the gap between the ink fountain and the blade, and affects the formation of deinking under the ink.
7) The water bucket syrup is too acidic or the amount of gum arabic is too much.

Approach:

1) Ink roll deinking caused by ink problems, black ink is more common. The ink produced from soot and black ash is oily and does not cause deinking. The black ink with carbon powder as the raw material is poor, deinking sometimes occurs, thinning some of the ink can be thinned, if the product image contrast, can not be adjusted when the ink is thin, you can drop some oleic acid in the ink solution.
2) The ink has low viscosity and is commonly used as a light-colored ink formulated by a lighter. The ink is easily emulsified. The acid in the water bucket invades the ink, corrodes the surface of the ink roller, and causes the ink roller to produce a hydrophilic layer, thereby discharging oil. For ink, thicken ink can be added to the ink to increase the viscosity.
3) After the occurrence of deinking of the ink roller, reduce the water content of the screen to reduce the acidity of the water bucket syrup and remove the gum arabic.
4) The ink is too thick and too hard, add No. 6 varnish to increase its fluidity.
5) Intensively agitate the ink fountain and remove the ink and impurities inside the ink fountain. Prevent the ink from drying or gelling. Prevent deinking.