The importance of water-like ink viscosity and control methods.

Viscosity is one of the important quality indicators of water-based inks, and it is also an important factor in determining the quality of printing. Ink viscosity is too low, easy to cause poor transfer, insufficient ink supply, printing uniform strip, transfer ink is not enough, dew white and other phenomena;
I, a correct understanding of the viscosity of water-based inks
water-based ink viscosity is generally standardized in ink products according to the type of printing, no need to provision before use, for user-personalized products, according to the actual situation of users customized or on-site deploymentIn the application of ink and water also has a certain cognitive misunderstanding of the viscosity of ink, the misconception is that the viscosity of ink can be diluted in a high proportion of use, so it can reduce printing costs, resulting in a series of quality defects in the printing.
water-based ink is composed of resin (water-soluble resin, colloidal dispersion, emulsion polymer), water, amines, pigments (organic pigments, inorganic pigments) and additives, according to the characteristics of the printed material, in strict accordance with a certain proportion.
From the figure above can be learned that water as the main solvent of ink is in a strict proportion of its existence, casually add water in ink, increase the proportion of water, dilute ink, in fact, changed the ink in a reasonable ratio of various components, destroyed the original performance of ink. Therefore, random addition of water in ink is the wrong operation, will inevitably affect the quality of printing.
This case because of the random addition of too much water in the special green ink, resulting in ink viscosity decline, color printing is not true, color saturation decreased, the print obviously appear color difference, small map is 200 times magnifying glass under the field photos, the color is seriously unevenly distributed, but also affect the ink on the print after drying conjunctivum quality, resulting in reduced friction resistance.
color satiety of the print mainly depends on the color content of the ink, the solid content and the colorability of its resin matching. The color content of pigments in normal ink (original ink) is sufficient to meet the printing cover requirements of preset ink layer thickness, per unit area ink, and a reasonable proportion of resin in the cooperation of various ingredient additives, can meet the printing process of ink uniform clothing, transmission and drying conjunctivation. Random addition of water destroys the performance of ink, dilutes the color content, destroys the state of color material in ink, while diluting the content of resin and other parts, changes the viscosity of ink, affects the transfer performance of ink, drying speed and the quality of conjunctivation, will bring a series of problems to printing operations and print quality.
flexo version of high-definition ink printing ink, it has a better fineness, coloring force, color display, with good mobility and viscosity stability. The fineness of ink is an intuitive index that reflects the coloring force, dispersion effect and storage stability of ink, and involves the particle size and fluidity of pigment particles. Generally for the same pigment ink, the smaller the particle size, the same volume of pigment surface area increased, so the cover capacity increased, the higher the coloring force; At the same time, the fineness of ink, printing ink layer can be thinner, the amount of ink per unit area is greatly reduced.
paints give ink color characteristics to meet the color requirements of printing. Water-like inks with organic or inorganic pigments to go through surface treatment, water-like ink pigment particle size requirements in 7.5-25 m, high-definition printing color paste should be less than 10 m (table below): Second, pigments must be alkaline (PH value of 8.0-9.5). In order to improve the stability of pigments in water-based connections, it is generally recommended to add surfactants to increase the affinity of resins and water and the wetting of pigments and water-based connecting materials. Organic or inorganic pigments in a certain ratio of surfactant wetting, dispersion under the action of the formation of a consistent, stable, with a certain amount of mobility, strong coloring strength of concentrated pigment slurry. It can be seen that the random addition of water in ink, will inevitably destroy the performance of ink.
can be seen from the table above, good ink fineness also needs a stable ink viscosity to maintain. Different printing needs to use different ink viscosity, more importantly, to maintain the stability of ink viscosity in printing operations.
2. Factors and solutions affecting ink viscosity
1, the effect of temperature on ink viscosity
the temperature and humidity of the printing environment will directly affect the change of ink, temperature rise, humidity drop will lead to the rapid evaporation of ink, especially in winter and summer temperature difference, the performance of viscosity is most sensitive. For example, in winter ink, stored in the summer use, ink viscosity must be re-detected adjustment.
Table 2 (Effect of temperature on ink viscosity)
Printers must attach great importance to the impact of ink temperature, before printing should be the temperature of the ink in the printing shop, this measure is very important, otherwise the ink viscosity in the printing process will have a more obvious change.
table 3 (the solution to changes in ink viscosity caused by temperature)
. 2.PH value on ink viscosity
The PH value of another indicator to be controlled in ink application, its normal range is 8.5-9.0, when the printing performance of water-based ink is the best, the print quality is the most stable. Ink in the printing operation process, continuous ink transmission system in the printing press to the ink barrel circulation, ink volatile components and water over time in the air volatilization, therefore, long-term use of ink will inevitably be due to changes in composition resulting in performance changes, resulting in a decrease in PH value, so that ink viscosity increased, drying speed is slower.
Table 4 (Effect of PH value on ink viscosity)
Table 5 (Effect of ink PH value on printing)
EFFECT of PH value on the suitability of ink printing, mainly in the viscosity stability and dryness of ink and dot clarity. In the process of use, because ammonia in the printing process constantly volatile, with the decline of ink PH value, ink viscosity increased, the drying speed is slow, will inevitably affect the normal printing work. Therefore, the operator needs to add new ink and various additives to the ink from time to time, the pH value of the ink will change as a result, the operator must master the principle and process of ink adjustment, do not arbitrarily add adjustments, ink suppliers will provide technical support. Using the standard PH value meter during operation, it is easy to measure the pH value of the ink and adjust it in a timely and accurate manner.
control the viscosity of ink, so that printing work can be sustained and stable, maintain the pH of ink, can stabilize the viscosity of ink.
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