Analysis and Exclusion of Printing Quality Failure of Green Packaging Ink

In the 21st century, the eradication of white pollution and the development of green packaging have become a trend in the packaging industry, and green packaging inks have also emerged.

Green packaging ink generally refers to the use of water-based and alcohol-based solvents instead of toluene, xylene as the solvent of volatile drying ink, used for plastic film, aluminum foil, leather, woven bags and other packaging materials gravure and flexographic printing, can reduce solvent evaporation Atmospheric pollution can also improve workers' operating environment. At present, there are more than 30 varieties of water-soluble gravure, flexo-printing, electrophotographic and photo-curable inks such as light, fast-fixing, rotating, and plastic in China, reaching more than 300 colors.

The green packaging ink has two major categories, liquid and paste ink, depending on the composition of the colorant, the binder, the filler, and the auxiliary agent. The application classification methods are as follows:

According to the printing plate type classification, there are flexible letterpress inks, gravure printing inks, and screen printing inks and roll coating inks. According to the main components of ink classification, can be divided into alcohol-soluble printing inks and water-based printing inks.

According to the use of ink classification. There are paper printing inks, plastic inks and so on.

In short, green packaging printing ink is an industrial product that serves packaging products and can be used for printing newspapers, magazines, food, packaging printing and decoration. In the following, the use of green packaging ink essentials and solutions to the printing faults are outlined. I would like to refer to my colleagues for packaging and printing.

In colloid chemistry, substances that reduce the surface tension of a solvent are called surface active substances. Based on this principle, we use rosin soap as a surface active agent for pigments to dissolve rosin and a non-polar polyolefin resin at a high temperature, which significantly changes the interfacial tension of the system and eliminates the need for corona. The roughened surface of the substrate has a firm adhesion. In our daily packaging and printing business, green packaging inks are relatively thin, and they are mostly used in operations such as flexible rotary relief, rotogravure, rotary screen printing, and rotary printing cardboard for single pneumatic diaphragm pumps. In order to overcome the layered sedimentation of the ink in the summer and thicken the winter ink jelly, which affects the normal printing, we add a network structure in the ink and can contain inorganic alcohol and organic high-efficiency dispersion materials in the lattice state of the hydrophilic alcohol-OH. Keep the ink in a stable state. Although sometimes stratified or precipitated like other printing inks, the ink properties can be restored by slightly stirring for 1-3 minutes. Faults caused by many factors such as ink quality, printing materials, operator skills, etc., can be summarized as faults, phenomena, and remedies.

1. Blurred graphics.

A printing ink layer is light, and the ink is not clear.

A small amount of ink, ink is hard, printing pressure is small, the ink transfer rate, adhesion is poor (sometimes even dry in the layout, ink roller or indentation hole), black ink even in the printing process, rough substrate surface .
Adjust the amount of ink and viscoelasticity, adhesion fastness, increase the printing speed, reduce the printing pressure, increase the ink and add high-efficiency ultra-dispersed additives, to improve the ink transfer rate, adjust the printing pressure and select the surface smoothing material, dilute the ink viscosity (Paint a 4# cup no lower than 15 S, preferably around 25 S) to increase the drying speed.

2, crushed and dirty.

An imprinted ink causes the printed product to become dirty.

A large printing pressure, poor layout flexibility or pressure roller deformation, not smooth.

Adjust the ink drying speed or reduce the amount of ink, reduce the pressure of the pressure roller, change the flexo plate and correct the pressure roller.

3. Dirty and bite.

The back side of a print is stained or overprinted by the previous ink, or the ink on the transfer belt of the impression roller is transferred to the next print.

An ink is too sticky, dryness is too slow, the second color is easy to stick off the first color, the surface of the conveyor belt is not clean or swollen, the printing pressure is too high, the machine speed is too fast, the thickness of the printing material is uneven on both sides or the winding tension Inconsistent.
Improve the initial dryness of the ink, add quick-drying solvents or oils, increase the proportion of lubricating and anti-adhesives in the ink (96:4); increase the air blowing or slow down the printing speed and extend the printing stroke; select good absorption or Surface roughening materials; improve the surface absorption of substrates; note that the stacking of the prints should not be too high or too heavy.

4. Ink splash.

One has different ink sizes in the printing shop. Dot or ink drop splash.
An ink has a large yield value, a large viscosity, an ink layer thickness, and an ink film thickness that is too long when the ink film is separated or the ink is too thin, the printer speed is too fast, the ink viscosity is too small and the electrostatic resistance is not good, the accuracy of the printer is poor, and the ink roller is deformed or Surface damage.

A change of the ink roller (according to the ratio of the number of printing plate lines and the anilox roller network line, choose 1:4 is appropriate), reduce the viscosity of the ink and reduce the drawing length and fluidity, reduce the ink supply, adjust the viscosity, and slow down the printing speed. , adjust workshop temperature and humidity, replace ink roller and repair equipment, or add antistatic facilities and materials.

5. Plate, ink roller sticky and scratches.

A plate and an ink roller are stained by ink on the printed material.

A small amount of ink and high viscosity, ink impurities, ink drying too fast or too slow; plate and roller on the electroplating layer wear or hardness is not enough, imprint too deep; paper and other plastic dust increases.

Replace the double-sided adhesive tape, adjust the pressure and adjust the angle between the doctor blade and the anilox roller, reduce the amount of ink or replace the ink, increase the quick-drying solvent or oil, repair the printing plate and roller, re-glaze the chrome, prevent paper, plastic The powder dust falls off.

6. Poor adhesion and scratching.

A print is easy to wipe off.

A paper, plastic material surface is too smooth and dense, not suitable for slow-drying ink; ink resin content is too small, poor surface treatment, can not dry and floating on the surface of the printing material and it is easy to wipe off, commonly known as "skin bone Health."

Improve ink type, adjust ink suitability, process printing materials, use sticky, high concentration inks; increase printing pressure, reduce ink film thickness, reduce printing speed; use high-efficiency additives and viscosity-increased inks and replace inks Dry gradients of solvents or oils, exchange of ink oils or thinners, should understand the suitability of inks.

7. Residual irritating odor

The proportion of methanol in an ink is too large or an odorous solvent or oil is used.

An ink minimizes or does not use solvents or oils that are irritating or harmful to human health at all.
Replace ink or replace solvent or oil

8. Inaccurate hue and precipitation of ink, a lighter color, discoloration, resulting in paste printing quality and sample does not match.

A pigment, filler and binder have poor affinity and store condensation or severe delamination (thinning and thickening).
Mix thoroughly before use. The ink should be stored in a cool, dry and ventilated place during the storage period. The tone can be adjusted or exchanged to the closeness of the sample hue. You can also add 1% to 3% of the white ink in the ink or increase the filler to increase the hiding power.

9. Pinhole and slippery.

Chemical pinholes appear in a printed image.

A full version of the spots and inks appear to overflow and foam during the printing process.

When the viscosity of an ink is too low, new ink or resin should be exchanged to increase the viscosity and increase the fluidity. To increase the printing speed, wetting and plasticizing defoamers should be added to eliminate foam. The pattern depth should be changed to 30mm.

10. Embedded version and orange peel.

An ink residue and dried in the plate cavity results in a watermark on the printed crystal and a poor print gloss on the orange peel.
One ink has large viscosity, many impurities, too fast drying speed, and poor leveling property; the auxiliary agent is not suitable for printing roller and paper, and the affinity between plastic films is not good; the printing speed is slow or there is static electricity.

One to adjust the printing speed, web high speed: about 0.012S, about 0.055S at medium speed, low speed: 0.09S, sheetfed printing: 0.0128 (required time on the ink transfer printing material) The blowing angle should be 90° or improve the ventilation conditions; add other solvents to improve the solubility of solvents or oils and inks; replace the ink additives; reduce static electricity and try to adjust the tone to a gray balance.

Consequences, just try it. Due to the differences in RIP, RGB images may only have black images on the separation film, no images on other color versions, and it may be that the information (dot) of the images on the four-color film is exactly the same, that is, the equivalent grayscale image. Although some distribution software or RIP can convert RGB to CMYK, it is best to use scan software or Photoshop to perform the mode conversion.