Full-effect water-based gravure plastic film ink printing report

First, how to use water-based ink correctly?

1. Characteristics of water-based ink:

(1) Effects of slow-drying on printed products: General water-based inks can be classified into two types, one containing alcohol (>10%), and one containing no alcohol or less alcohol (<10%). No matter what kind of product, it is a slow-drying ink for solvent-based inks. The slow-drying ink under the action of water will cause great difficulty in the drying of the ink, and the printed products will cause problems such as sagging (water wave), back sticking, and uneven transfer. In general, the higher the content of ethanol in the ink, the lower the probability of occurrence of the above problem (except isopropanol).

(2) The effect of the transfer rate on the printed products: the same ink, different solid content, the ink transfer rate is not the same. For the release of pigments, there is a difference in the content of the resin and the transfer rate. High resin content (>30%), high transfer rate of the shallow plate; low resin content (<25%), high transfer rate of the deep plate. How to do a high-profile to low-key version (dark tone) of the transition, which is the water-based ink to solve the problem. Otherwise, due to the uneven transfer rate, it is difficult to print gradation effects.

(3) The influence of solubility on printed products: In water-based inks, water is not a true solvent, that is, water cannot be dissolved alone. The so-called water-based ink, in which water is not a continuation of the continuous phase, is not a continuous disperse phase. For this reason, when water is added to the ink, it needs the assistance of other factors to make the water evenly dispersed in the ink. The use of water-based inks, like solvent-based inks, can be added more liberally than thinner. Otherwise, it can be said that there will be uneven transfer, uneven color development, and poor dispersion.

(4) Effect of hiding rate on printed products: Due to the characteristics of water-based inks using resins and pigments, color inks are often more transparent. This has the problem of insufficient coverage. The method of increasing the content of pigments can solve some problems, but at the same time, it also has negative effects such as high viscosity and large thixotropy. Therefore, if a printing company has a high demand for cover, it should submit it to the ink maker.

2. Standardized print jobs:

(1) Preprint work elements: Prepress work is very important and it is an important factor in determining the quality of printed products.

1 Inking: Unlike solvent-based inks, water-based inks cannot be diluted as much as solvent-based inks. Since water is not the true solvent of the resin, there are two points to note when diluting: First, it is not appropriate to dilute it while printing; first, it is not appropriate to add more than 8% of thinner at a time. The standard practice is: determine the drying conditions (>55 °C), determine the printing speed (such as 40m/min), determine the plate depth (such as 35μm), the first dilution of 5% of the water in the barrel, stirring for 10 minutes , Diluting 5% of water and stirring for 10 minutes, you can prepare for printing on the machine. The printing viscosity at this time should be adjusted to 18~20s. If you need to adjust the viscosity again, dilute 5% to 10% of the water in the ink tank as before.

2Adjust the scraper: It is appropriate to adjust the distance between the primary cutter and the secondary cutter to 0.3cm. The knife angle is set to 60~120 degrees (according to the actual confirmation).

3 Thinner: The adjustment of the thinner is very important, not sloppy. The most basic is to adjust the pH of the water to a suitable range (eg, 9) and adjust the water tension if possible. This is very good for printing. Many people think that as long as they add water, it is unscientific. Diluent adjustment formula should be adjusted according to the requirements of ink manufacturers, so that it is targeted.
4 Thin film: The material is required to be flat, uniform in thickness, and can not have a folding or dead mark. The corona requirement is above 38 dyne.

(2) The working elements of India: The operation of water-based ink in the printing process is very convenient. To keep the quality of printed products stable, we must pay attention to three aspects.

1 pH stability: The general water-based ink requires a pH of 8 to 9.5. Because ink manufacturers consider factors such as drying, water resistance, and cost, the pH balance agents used are often fast volatile materials. This can easily cause changes in pH, so be aware of changes in pH during use. The printing plant should purchase the corresponding equipment, such as a pH test pen, to track the ink in the ink tank. The instability of the pH value directly affects the quality stability of the printed product.

2 Viscosity adjustment of water-based ink: Before printing on the machine, ink viscosity has been adjusted, but in the printing process, the viscosity of the ink must be tracked, such as water to adjust the viscosity, one-time addition of water can not exceed 5% It is best to operate at a ratio of 3:7 (alcohol:water). We often make empirical mistakes. We use solvent-based inks to use inks. There are many diluents that are added at one time. We do not measure the dosage accurately. This is unscientific. The viscosity adjustment of the water-based ink can be observed and adjusted once every 4 hours.

As long as the pH and viscosity are well controlled, the printing quality of the water-based ink will be relatively stable.

3 pressure rod adjustment: PE low pressure membrane pressure is slightly larger, depending on the condition of the equipment. The faster the printing speed, the greater the pressure.

4 winding: winding tension should not be tight, that is to say the tension can not be too large, winding diameter can not be too large, should not exceed the diameter of 55cm.

5 plates and ink tank: If you need to stop printing, the plate can not be too long time away from the ink tank, because the water-based ink resin is often not soluble, which is fundamentally different from the solvent-based ink.

6 blade cleaning: 8 hours cleaning time, can be operated on the machine.

India must prepare the material: pH pen / viscosity cup (3 #) / light oil / ethanol / paste / measuring cup (10,50,100,500,1000 L).

(3) The post-print work elements:

1 false dry detection: As water-based ink is often used as a pH adjuster ammonia, and in the process of drying volatilization, ammonia is not completely volatilized, about 30 to 40% of the ammonia is still in the ink layer. When the amount of ammonia in the ink layer reaches 0.3, it is very easy to appear as a “pseudo-dry phenomenon”, and even this material will have a bad influence on printed products after printing, and the most prominent thing is “back-gluing”. An effective way to solve this problem is to dry the product at 70°C for 1 hour after it is printed.

2 Adhesion testing: random initial test (adhesion area of ​​90%) - 12 hours test (adhesion area of ​​100%)

3 Water resistance test: 1 hour test (wet wipe 10 times without ink) --- 24 hours test (wet wipe 20 times without ink) --- seven days test (wet rub 30 times without ink). Or on request testing.

4 other tests.

The performance of the water-based ink is generally 7 days. Longer than solvent inks.

3. Requirements for the printing plate: The plate depth is set between 25 and 35 um. Hardness is greater than 800. The basic requirements for production of the edition are:

Version 1 depth is between 15 and 25 μm: a cylindrical version with 150-160 meshes and a 45-degree inclination.

The 2nd edition is a cylindrical version with a depth between 25 and 35 μm: 90 to 110 mesh and a tilt angle of 45 degrees.

3 The fineness of ink is between 10μm and 15μm, and it is better to use dots with more than 170 meshes. The fineness of ink is between 5μm and 10μm, and it is better to use the dots with more than 190 meshes.

4 Intaglio tone ratio: Due to the slow drying and low viscosity of the water-based ink, the ink in the gravure cavern is almost not dry, so the transfer of the high-profile site is good, and the transfer of the dark part is poor, and the contrast of the level is weakened. . The solution is to adjust the depth of the middle of the cell so that the middle of the plate is adjusted to the depth of the cell of the highlight. Generally, it is shallower than the solvent type.

4. Printing failures and solutions:

(1) Fog and paste:

Reasons: When printing at a higher speed, water-based inks tend to produce fog and stencils. This is due to the slow evaporation rate of the water-based film. The film attached to the surface of the gravure cylinder is easily transferred to the substrate, and then the ink. The tank is mixed with powder, or insoluble matter due to precipitation of the resin, increasing the resistance of the blade, so that the blade cannot scratch the plate surface.

Solution: Filter the ink, add a proper pH balance agent, increase the pressure of the squeegee (do not use as much as possible), and improve the production accuracy of the plate.

(2) Precipitation of resin: Cause: Overdiluted, pH unbalanced, incorrect diluent added. Solution: Adjust the pH and filter the ink.

(3) Slow drying: Reason: The viscosity is too high and the oven temperature is insufficient. Solution: Reduce viscosity, increase oven temperature and wind power. Note: If four colors are overprinted, the drying speed of the water-based ink is 4 to 5 times that of the solvent ink. Using a water-based ink, the drying speed of the plate at a depth of 20 μm was almost the same as that of a solvent-based ink at a depth of 38 μm.

(4) Ripple: Cause: Dilution too much, too low viscosity, too slow print speed, uneven film. Solution: Add resin, color paste, and increase printing speed.

Second, how to reduce the cost of water-based ink?

The reduction of the use cost comes from four factors. One is to increase the yield of printed products, the other is to reduce the amount of ink on the ink, the first to reasonably use power, and the first to protect the printing plate and scraper.

(1) How to increase the yield of printed products:

1 Strictly ensure the stability and balance of pH: During the entire printing process, the pH of the ink after dilution should be guaranteed between 8.5 and 9. Too low ink will thicken the ink, drying it slow, and prone to "pinholes", even resin precipitation, the emergence of particles, and affect the print product's water resistance. Excessive pH value is prone to "sagging" and other phenomena.

If the above elements can be effectively implemented, the quality of printed inks of water-based inks is more stable than that of solvent inks, and the quality of printed products can be effectively guaranteed to achieve the purpose of cost reduction.

(2) How to reduce the amount of ink used for ink-jet printing: Due to its own drying, water-based ink manufacturers tend to increase the pigment content of ink ink during production to meet the needs of shallow printing. For example, a 40 μm version of the deep gravure is used for the solvent ink, and a 30 μm version of the deep gravure is used for the water-based ink. The effect of the print is basically the same. Based on this calculation, the amount of ink on the water-based ink is about 25% lower than that on the solvent ink to offset the difference in the selling price. Therefore, the use of manufacturers should adjust the depth of the plate when appropriate.

(3) How to reasonably consume electricity: The main power consumption is from the oven. The rational design of the oven determines whether energy can be saved. The oven used in the original solvent ink printing should be properly modified to achieve energy reduction. The author has tested that if the oven is changed to an external heating type, the heat energy can be reduced by 40%.

(4) How to preserve the plate and scraper: Selecting water-based ink is a prerequisite. The water-based ink sold on the world, and some because of the ink itself, are very detrimental to the version, but some water-based Ink does not hurt the version does not hurt the knife, in the trial, the printing manufacturers must consider this factor. In addition, it is necessary to control the squeegee pressure during printing. If the squeegee pressure is too high, the ink on the stencil can be scraped. It is recommended that the printing manufacturer change the supplier.

Description: 1. Related to the full effect of Yeye: HL-18 waterborne resin, HL¬318 waterborne dispersant, HL-40 color paste, HL-218 multi-functional additives.

2 Strictly ensure the stability of the viscosity of the ink system: Before printing, adjust the viscosity of the ink on the machine, and add the water thinner directly into the ink grain during printing. Be careful and the proportion must be strictly controlled within 3% to 5%. And special personnel are responsible for preventing multi-person management. The stability of viscosity plays a decisive role in the stability of the quality of printed products.

3 Reasonable deployment of thinner: The water-based ink thinner cannot be simply seen as "water", which is the wrong concept. In fact, in the water-based ink thinner, in order to better balance all aspects of the factors, it is necessary to add appropriate additives, which requires the printing manufacturer to do the job according to the ink manufacturer's requirements. In general, proper pH balance, viscosity balance, and water-oil balance should be added to the diluent.

The production of gravure water-based plastic film ink has been proved by practice, can be applied to BOPP, PP, PE Yuan high and low pressure, PET, NY, PVC, EVA, cellophane, non-woven, all kinds of white paper, kraft paper and other printing, Therefore, it is called Yezhe.

2. Three-point printing ink seven points: the use of water-based ink, its approach and elements, compared with solvent ink, there are many different. In other words, no matter how good the printer is, if it is not trained, it is difficult to print good prints. As far as the status quo is concerned, the printing and training responsibilities of ink and wash are to be borne by the ink-and-wash manufacturers.