Postpress ink treatment

1, poor whiteness

Phenomenon: After printing, the surface of the ink is gray or yellowish.

Cause: The whiteness of the titanium dioxide used in the ink is not good, the color of the connection material is too dark, and the color is affected; the amount of the baking temperature, yellowing, brightener, and colorant is not enough. The manufacturing process introduces dirty colors.

Solution: The surface of pure white titanium dioxide is added to the ink. It is best to use rutile titanium dioxide that is not yellowed, has good stability and good hiding power, uses resin oil with very light color, or uses such resin oil to adjust ink properties; Strictly control the baking temperature and time, avoid overheating and baking for a long time; adjust the color of the cold-adjusting colorant (indigo blue, ultramarine blue) or adjust the amount of warm-colored agent (purple, chrysanthemum, and magenta 6B) to make the coating Looks whiter; strictly clean the printer, prevent cross-colored or mixed with other colors, the pressure is not too much, otherwise it will cause the friction to turn gray and black.

2, powdering

Phenomenon: The ink film after roll coating, lightly rubs off the toner, dimming.

Reason: Because the resin does not wrap the pigment resin well; the amount of pigment is large and the amount of resin is large, and the resin cannot wrap the pigment well to form a bright ink film.

Solution: Increase the amount of resin and redistribute the ink; when it has been painted and found early, it can be covered with a light varnish.

3, orange peel

Phenomenon: The surface of the coating forms an orange peel-like texture.

Cause: Due to the wide boiling range of the solvent, there are many parts that evaporate quickly. After the roll coating, the ink has not yet leveled. It is also due to this reason that the leveling is hindered, so that the surface is uneven. As the resin used for the ink is too small, the cohesion force is large and the leveling property is not good.

Solution: Leveling agent for high dissolution range and improved leveling performance, such as octanol, etc.; Increased flowability of castor oil alcohol resin, improve ink flatness.

4, flow hanging

Phenomenon: After the roll coating, put the printed product on the rack, or after drying, see the ink flow together, and there is a shape concentrated in a certain place, not smooth, poor light.

The reason is that the ink is too thin and the leveling property is not good; the ink is too thick and the leveling property is not good, and the specific gravity is too large.

Solution: Adjust the viscosity of the ink so that after it has been painted, spread it around during the flow. Improve the cohesion of the ink so that it does not shrink into a line due to the leveling. Adjust the viscosity to an appropriate level, not too thick or too thin.

5, exposed

Phenomenon: After the roller coating, the metal ink layer is not thick, can see the aluminum pipe or aluminum pipe stretch marks, or leave a blank line that exposes the metal pipe color after the roller roller leaves.

Cause: The viscosity of the ink is too small, the hiding power is small, and the pressure is large. That is, the distance between the roller and the hose is too small, and the adhesion of the ink to the metal is too small.

Solution: Adjust the ink viscosity to 85~95 seconds/25°C, not lower than 60 seconds/25°C, adjust the roller coating pressure properly, increase the amount of ink. Add epoxy or alkyd resin that is good for pipe adhesion.

6, fracture, shedding

Phenomenon: After the roll ink coating is dried, the ink layer is cracked or powdered and the metal tube is exposed when the contents are squeezed at the bottom sealing mouth and in use.

Reason: After the ink layer is dry, it becomes a hard and hard coating. This is mainly due to too much desiccant added; the resin used is too brittle; the white material content is too high. The ink is too thick and the ink layer is too thick. Baking temperature is too high, too long will form a flexible film.

Solution: When adding dry oil, try to reduce the amount of ink that is baked to form a flexible film. It is necessary to go through some tests to obtain local conditions; for the disadvantages of the brittleness of the resin in ink, it should be transferred into the plasticizer. Dibutyl phthalate, or with flexible resins such as alkyd and amine groups; reduces white pigment content, so as not to affect hiding power and whiteness. Baking temperature can not be too high 80-90 °C is appropriate, the time can not be too long, 25 to 30 minutes can be.

7, pinhole

Phenomenon: After the roll coating there is a small hole through the bottom, as with a pinhole.

Reason: Due to the large surface tension of the ink, the metal pipe is not well-humidified, or the oil on the metal pipe is too repulsive to the ink; due to the improper proportioning of the solvent, especially the solvent that evaporates quickly, it violently rushes out to form a vortex; the ink is mixed with a lot of bubbles The bubble burst during baking; the small particles with incomplete dissolution in the ink binder have the same charge as the pigment and are mutually repelled and dried. These factors can cause holes that penetrate the bottom.

Solution: First use the scrubbing method to make the metal tube clean; add a quick-drying, slow-drying solvent with appropriate proportion to ease the evaporation rate; add the solvent to reduce the surface tension or slightly reduce the viscosity to fully infiltrate the ink and metal; uniform The distance between the ink and the transfer roller is reduced, so that the bubbles in the ink are broken and then printed evenly.

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