Water Based Ink Composition

This series of water based ink composition are widely applied in the continuous printing on web papers with gravure machine and flexographic machine.

Production process of water based ink composition

The first step is grinding to prepare color paste: mix water-soluble resin, pigment, additives and solvent (water), stir, disperse and grind into standby color paste through high-speed disperser.

The second step is to prepare ink: mix the standby color paste, additives and solvent (water) evenly, grind and disperse them to make them have sufficient fineness, luster and coloring power. The filter packaging is the water based ink product.

Usage Method

1. After opening the lid, stir slowly with a wooden stick from the bottom of the barrel for about three minutes until the color at the bottom turns up. Because the ink is oil above and ink below, if it is not stirred evenly, it will cause instability when the ink is used next time. The color of the poured oil is not ideal when printing.

2. After full stirring, the amount of ink used is determined according to the number of printing paper pieces. If there are not many pieces of paper to be printed, do not open the whole barrel of ink immediately. But how much ink is poured out. After pouring out, cover the ink bucket again to avoid volatilization.

3. Check the viscosity of the ink. If it is thick, add an appropriate amount of water. Water addition ratio: add 500-800 ml of clean water to the whole barrel of ink, which will not affect the printing effect, but only increase the fluidity of ink.

4. Ink can not add too much water, which will blister, especially in spring and summer, will produce bubbles and precipitation, which is what some users call impurities. If the customer's requirements are not high, the ink can be added with more water. First, add an appropriate amount of ink in the whole barrel, and then add water, stir it for printing. Do not add excess water in the whole barrel, otherwise it will blister, and then add defoamer.

5. If the ink barrel is not tightly covered, the ethylamine of the ink will volatilize and the pH value will be reduced. If the ink at the bottom of the barrel is found to be like paste, it means that the ink needs to be restored, otherwise the ink suction pipe will be blocked. At this time, do not add water. Adding water will affect the printing color. Add reducing agent for reduction, that is, increase the pH value of the ink.

Water based ink composition has been used as a color material. However, in the water based ink using dyes, it is easy to produce image color penetration, and the improvement of light resistance and water resistance is also restricted. In order to overcome these shortcomings, aqueous inks using pigments as color materials have been used in recent years. In aqueous inks using pigments, the composition needs to be stably dispersed in an aqueous medium. Therefore, water based inks and pigment dispersions that become raw materials of water based inks usually use dispersants to improve the dispersion and dispersion stability of pigments.

Problems and solutions of water based ink composition in gravure printing!

Water based ink composition is one of the most environmentally friendly printing inks today. It is also the only printing ink recommended and approved by FDA and can be used in direct contact with food. In China, although the water based ink for paper printing has been commercialized, it is still in the initial stage of research due to the non absorption of film in a large number of plastic film printing for food packaging.

On the basis of maintaining the same printing quality as solvent ink, a good water based gravure printing ink must achieve zero VOC emission; Must have good printability; Be able to print on the surface of various substrate materials; At the same time, it is also hoped that the cost of this printing ink is relatively low.

The use of water based gravure printing ink will cause problems such as changing the engraving of gravure printing roller, changing the operation of printing machine, maintenance of printing machine, replacement of dryer and so on. Similarly, the substrate material will also strongly affect the printing effect of ink, especially for the printing of substrates with low surface tension, such as plastic film material and coated paper surface. For uncoated paper, ink may even lead to paper deformation and curl. These problems do not exist for solvent gravure printing ink.

Some common problems often occur in the process of gravure printing with water based ink composition. This article will introduce the current processing.

Ink gravure printing problem 1: blocking

In the process of using water based ink, blocking is the most likely problem, mainly because the re solubility of gravure water based ink is poor, so it is very easy to block once it is misoperated. Blocking will lead to a series of printing quality problems, such as pinholes on the printing surface, small text missing pens and paintings, uneven ink color, bottom leakage and so on. The causes and solutions of blocking are as follows.

1. Stop the printing plate intermittently, and the ink dries and solidifies in the mesh hole due to the volatilization of diluent. At this time, the printing plate shall be cleaned with special tools and cleaning agents. If necessary, the printing plate shall be removed and cleaned with organic solvent (ethyl acetate). Therefore, in case of intermittent shutdown, it is recommended to stop the version without stopping, so as to prevent the ink from drying and fixing in the mesh hole.

2. The ink dries and solidifies in the net hole instantly due to too fast drying. In this regard, first, a small amount of slow drying agent can be added to the ink. The slow drying agent can inhibit and slow down the ink drying time and prevent the scaling on the ink surface. The general dosage is controlled at 3% ~ 5%; Secondly, consider whether the diluent ratio is appropriate. If necessary, adjust the diluent ratio. Generally, the ratio of alcohol and water in the aqueous ink diluent is between 1:1 and 4:1, but the amount of water needs to be considered when increasing the ratio of water. If the amount of water is too much, on the one hand, too many bubbles will be generated, on the other hand, the ink will not be completely dried, Make the printed matter sticky or ink pull back.

3. The ink viscosity is too high. At this time, the ink viscosity should be properly reduced, but both printing speed and leveling must be considered. Because the ink viscosity is too low, too many bubbles will be generated, resulting in problems such as white spots on the surface of printed products, too light color of printed pictures and texts, or thick thin lines and small words.

4. The printing plate mesh hole is too shallow. At this time, the depth of the printing plate mesh hole should be properly deepened, but the quality problems that will occur when the printing plate mesh hole is too deep must be considered, such as coarser handwriting, blurred small words, unclear patterns and so on.

Ink gravure printing problem 2: poor drying

Drying performance is one of the most important indexes of water based ink. The drying speed of water based ink is slower than that of solvent based ink. Once it is not dried enough, it will produce roll sticking phenomenon.

Therefore, when using water based ink, the drying temperature must be increased, which is usually 10 ~ 20 ℃ higher than that of solvent ink. At the same time, the exhaust air volume needs to be increased. If possible, the post printing paper passage can be extended. Of course, the improvement and promotion of the drying performance of water based ink also need the cooperation of ink manufacturers to adjust the formula of water based ink.

Ink gravure printing problem 3: dirty brace on printing plate

In the gravure production of water based ink composition, there are often dirty pull strips around bar codes or dark graphics and texts because the ink on the printing plate at the corresponding position is not scraped clean, mainly because the lubricity of water based ink is lower than that of solvent based ink.

In this regard, the ink manufacturer needs to add corresponding additives when producing water based ink. At the same time, the printer needs to adjust the angle and pressure of the scraper in the printing production, and the shorter the blade when installing the scraper, the better the ink scraping effect. Qualified printing enterprises can consider using ceramic scraper, which has smooth blade, no grinding, good elasticity and corrosion resistance, and the blade part can fit perfectly with the printing plate cylinder after unique polishing treatment, so as to achieve the best ink scraping effect.

The aqueous ink composition is a uniform mixture composed of colored body (such as pigment, dye, etc.), binder, filling (filling) material, additive, etc; It can be printed and dried on the printed body; It is a paste adhesive with color and certain fluidity. Therefore, color (hue), body bone (rheological properties such as thinness and fluidity) and drying performance are the three important properties of ink.

Test items:

Ink color detection, liquid ink fineness detection, ink coloring power detection, liquid ink viscosity detection, liquid ink gloss detection, liquid ink initial dryness detection, ink viscosity detection, ink viscosity increment detection, liquid ink adhesion fastness detection, liquid ink anti adhesion detection, ink harmful substances detection, ink heavy metal detection, offset ink fluidity detection Offset printing ink conjunctiva drying detection, light resistance detection of water-based ink composition, limit detection of ink soluble elements, color and transparency detection of ink, ink reflection density and chroma detection report, ink viscosity detection, water-based ink composition resistance to various media, etc.

Aging test:

UV aging, xenon lamp aging, neutral or acid salt spray test, heat stability, light resistance, liquid medium resistance, etc;

Ink performance test: color, gloss, fineness, viscosity, initial dryness, coloring power, adhesion fastness, anti adhesion, fluidity, conjunctival dryness, etc;

Pigment performance test: content, pH value, relative density, oil absorption, whiteness, sieve residue, coloring power, hiding power, dispersion, washing fastness, fluidity, etc;

Dye performance test: content, fineness, viscosity, ash, moisture, solubility, solution stability, bulk density, levelness, migration, fixation rate, discharge, migration, dust flying, etc.

Test standard:

GB / T 18752-2002 thermosensitive color changing anti-counterfeiting ink

QB / T 2825-2006 flexographic water-based ink

QB / T 2993-2008 erasable ink ball point pen and refill

GB / T 26394-2011 waterborne film gravure composite ink

QB / T 2024-2012 Gravure plastic film composite ink

QB / T 2025-2013 lithographic iron printing ink

QB / T 4538-2013 water based flexographic high temperature resistant preprint ink

Handling process of inspection report of water-based ink combination material:

1. Consult to confirm whether the requirements can be met (confirm the test items, costs, cycles and other issues)

2. Fill in the test application form

3. Arrange samples (send samples to be tested by express delivery, and the number of samples sent for different products shall be determined by the testing personnel)

4. Arrange testing after receiving samples (completed by the testing department and reporting Department of environmental testing laboratory)

5. Confirmation of draft report (draft report will be issued for confirmation after the test report is completed)

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