Ink properties and process precautions

Chemical and chemical properties
the chemical properties of ink mainly refer to its density, fineness, transparency, gloss, light resistance, heat resistance and acid, alkali, water, solvent (alcohol) resistance.
density
refers to the weight of the ink per volume at 20 degrees C. In g/cm
3
indicates
's
. The density of ink is determined by the type and proportion of raw materials applied in ink, and is influenced by the outside temperature. The density of ink has a certain relationship with the printing process. The density of ink is related to the amount of ink used in the printing process. Under the same printing conditions, the amount of ink with high density is greater than that of ink with low density.
density of inks is too high, mainly due to the high density of pigments in inks. In the printing process, because the connecting material can not drive the density of pigment particles to transfer together, so that pigments and other solid particles piled up on the surface of ink rollers, plates, or rubber cloths, forming a blocking phenomenon. Especially in high-speed printing or ink thinning, the use of dense inks is more prone to this phenomenon. At the same time, when the dense ink is mixed with the low density ink, if the gap between the two is too large, it is easy to produce the phenomenon of ink layering. Low density ink floating, high density sinking, so that the color of the ink surface is biased towards the density of small ink, the color of the bottom ink is biased towards the density of ink. In general, the density of printed inks is between 1g/cm
3
and 2.25g/cm
3
3.
fineness
refers to the degree of dispersion of pigments, fillers and other solid powders in the ink in the connecting material, also known as dispersion. It shows the size of the solid particles in the ink and the degree to which the particles are distributed in the connecting material. The fineness of the ink indicates the subtlety of the solid particles and the uniform distribution of the solid particles in the ink. The fineness of the ink is determined by the degree of wetting of the connecting material to the pigment and other solids, as well as the fineness of the ink after mixing and rolling.
the fineness of the ink is related to the fluidity, flow and stability of the ink, and is an important quality index. The fineness of the ink is poor, the grain is thick, and the printing will cause the phenomenon of blocking the plate. Damage to plates and scrapers can occur in offset and concave plates. And because the dispersion of pigments is not uniform, the intensity of ink color can not be fully played, affecting the coloring force of ink and the degree of lightness of the ink film after drying.
Transparency
is the degree to which the ink refracts (transmission) the incoming light. Transparency in printing refers to the degree to which the bottom color of an object can be displayed when the ink is evenly coated into a thin film. Ink transparency is low, can not make the background color fully appear, it will cover the base color to a certain extent, so this performance of the ink is also known as cover force. The transparency of the ink is inversely related to the covering force, and the transparency is expressed by the thickness of the ink layer when the ink completely covers a certain background color, indicating that the greater the thickness, the better the transparency of the ink and the lower the cover.
the transparency depends on the difference between the pigment and the refractive index of the connecting material in the ink and is related to the dispersion of the pigment. The smaller the refractive index difference between pigments and connecting materials, the better the dispersion of pigments in the connecting materials, the higher the transparency of the ink.
gloss
gloss refers to the ability to reflect light in the same direction when the ink on the surface of the print is dry. Inks with high gloss are shown to be bright in print. Gloss degree is mainly determined by the type and nature of the connecting material in the ink, the treatment of the refining process in ink manufacturing and the degree of flatness after the drying of the ink film. In addition, the gloss of the ink is also affected by the nature of pigments in the composition of the ink, the size and dispersion of particles, the permeability, leveling, dryness and other properties of the ink, the influence of the substrate and so on.
light resistance
refers to the ability of inks not to change color when exposed to sunlight. The light resistance of the ink indicates the degree to which the print fades or discolors in light. Light-resistant ink printing, although long-term exposure to daylight, but the printing of small degree of discoloration; In ink grading, level 8 is the least prone to discoloration, the best light resistance. The light resistance of the ink depends mainly on the pigment. Ink's light resistance has no effect on the printing process, mainly related to the printing process.
heat resistance,
heat resistance refers to the ability of the ink to not change color when it is heated. Strong heat resistance indicates that the ink does not change color when the print is heated to a higher temperature. The heat resistance of inks depends mainly on the type and properties of pigments and connecting materials. Some pigments not only change color, but even change when heated.
Chemicality
this performance refers to the ink under the role of acids, alkalis, water, alcohols or other solvents, color and performance does not change, also known as ink resistance or resistance. Ink chemical resistance is strong, in acid, alkali and other substances under the role of color and ink properties will not change. The chemical resistance of inks is determined by the type and performance of pigments and connecting materials, and is related to the state of pigment and joint binding, and to the stability of inks.
printing suitability
printing materials, printing inks and other materials to match the printing conditions, suitable for printing performance, called printing suitability.
the printing suitability of the ink, which means that the ink matches the printing conditions and is suitable for the performance of the printing job. Mainly has viscosity, adhesion, tentacles, dryness and so on.
the viscosity of the ink
the internal friction characteristics of the ink in the flow, called the viscosity of the ink, measure the physical amount of the viscosity of the ink, called the viscosity of the ink.
the viscosity of the ink can be measured by the viscosity meter, the commonly used viscosity meter has a parallel plate viscosity meter, rotary viscosity meter, Lare viscosity meter and so on.
the speed of the printing press, the greater the fluidity of the ink and the less viscosity.
the viscosity of the ink, which can be adjusted with ink-adjusting oil or ink thinner.
Ink adhesion
Ink from the ink bucket to ink rollers, plates, (rubber cloth) substrate surface transfer, ink film first split, and then transfer, ink film in this dynamic process to show the ability to prevent the cracking of the ink film, called ink adhesion. The physical amount of ink adhesion, called the Tack value of the ink.
the Tack value of the ink can be measured using the ink adhesive instrument.
printing process, if the adhesion of ink and the performance of the printing material, printing conditions do not match, paper will occur powder drop, hair, ink overprinting, printing dirt and other printing failures.
the adhesion of the ink, it can be adjusted with a adhesive or ZY ink additive.
The tentacleability of the ink
at a certain temperature, after stirring or applying mechanical external forces, the fluidity is improved and the viscosity decreases;
printing process, if the ink's tentacles are bad, it will occur "under the ink is not smooth", uneven ink transmission, network serious expansion and other printing failures. In order to prevent the occurrence of the above faults, it is necessary to use an ink shovel often stir the ink in the ink bucket or install the ink mixer in the ink bucket from time to time to stir the ink.
the drying of
ink is more complex, mainly in the following three forms.
seeped dry. The connecting material in the ink, some of which penetrates into the bearing, and the other part, together with the pigment, is solidified on the surface of the bearing and dried. High-speed roll paper printing press using non-thermo-solid rotating ink, generally to penetrate drying-based, mainly printed newspapers, periodicals.
oxide polymerization dry. The connecting material in the ink and the oxygen in the air are polymerized and dried into film on the surface of the insemination. Offset printing bright resin ink, bright color, good gloss, mainly to oxidation polymerization drying, for printing high-grade fine offset printing products.
is volatile and dry. Part of the connecting material in the ink evaporates into the air, and the remaining connecting material, together with the pigment, is solidified on the surface of the bearing and dried. Gravure printing ink is the use of hair-waving solvents as a connecting material, the use of the connection material is harmful to the human body benzene, xylene. Flexible printing, reduce the pollution of the environment, very promising. Volatile dry inks are particularly suitable for printing non-absorbent film materials such as plastic films, foils, etc.
addition, ink drying also has UV, infrared, thermal curing and other forms.
the drying of many inks, often combining two drying forms to dry the ink film. For example, a single sheet of paper fast-fixing offset ink, suitable for printing general offset products, it is using a combination of penetration and oxidation polymerization for drying.
printing process, if the ink drying is not good, will cause the back of the print dirty, sticky pages, ink film non-glossy, ink "crystallization" and other printing failures.
to speed up the drying of the ink, a drying agent can be added to the ink. Commonly used drying agents are: cobalt dry oil, manganese dry oil, lead dry oil and so on. In order to reduce the drying speed of the ink, a drying inhibitor can be added to the ink.
manufacturing process
ink manufacturing process can be divided into two stages: pre-dispersion of stirring and fine dispersion of grinding. The former mixes the matching pigment and the connecting material into a slurry in the container, while the latter still needs to be finely ground and dispersed in the stirred slurry to overcome the pigment's cohesion with greater mechanical pressure and shear force, and eventually become a suspended collosite-like ink.
Note
the deployment of ink colors is an important work before printing, but also very abstract work. Simple color material three primary colors, yellow, ma
green adjustable out of red, orange, yellow, green, green, blue, purple and other dozens of colors. In the actual deployment process, only rely on the three primary color ink can not obtain the color, this is because the ink manufacturers selected pigments, dyes simply can not meet the international standard of three primary color saturation, color concentration, brightness, etc. , the three original color ink can only be added to tea gray, not black. Therefore, in the actual coloring process can not be separated from black ink, white ink, lighteners and other inks and additives.
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