How to control the plastic gravure printing ink viscosity problem
In Plastic Intaglio Print , How to control the ink viscosity is a very key issue. Especially in the high-speed rotary intaglio printing, the ink viscosity control of the adequacy of the printing, direct transfer of pigments, dirty version, the printed product glossy brightness, color fastness bonding, electrostatic and other great majority of relationship quality and affect Prints yield and efficiency. Then, in the plastic gravure, how to control the ink viscosity to take into account various aspects, to ensure printing quality. This requires that we first understand the ink viscosity and viscosity these two concepts. According to the investigation related to materials or information, an overview of the relationship between the two are usually very vague, and some even put them both as a concept, in fact, there is a clear distinction between the two, the following points to explain inductive ink stick degree with distinction and contact adhesive.
1. The definition of different If for some reason makes the ink outside the flow of different levels, particularly in the two contact surfaces of liquid flow velocity in different layers exist between the force and reaction force, which is known as the ink inside the friction force, its as shown by the nature of the ink viscosity. Measure the physical quantity known as the viscosity of ink viscosity.
2. Expression differences Ink viscosity in the membrane resistance when, and only when the fluid flow only in the performance of a viscous, static fluid viscosity is not present. The role of viscous fluid within the performance of the sliding block to block fluid flow, but the role of this block can only delay the process of sliding can not make it stop. This is an important characteristics of viscous fluid, and it is a rheological parameter that the fluid within the adhesive properties. The viscosity of liquid by the external force in moving performance, the molecules within the friction generated by the measurement. Fluid viscosity is a property, whether at rest or fluid flow, it is always there.
3. Detection methods, different units Viscosity is to measure the rotation viscosity meter. Measured with a viscous ink or link to material produced by separation of the resistance film size, with the numbers indicate the value shall be viscous. Viscosity has no units.
There are many methods of viscosity measurement. In general there is capillary viscometer, viscometer orifice, rotary viscometer and other rotating cone plate viscometer. In general, commonly used to measure rotational viscometer the viscosity of ink. By the viscous fluid when the rotor resistance, the springs produce torque, and viscous resistance to contend, the final balance, this time with the gossamer connection pointer in a certain scale disk reading instruction (ie, the twist angle hairspring). The reading is multiplied by the coefficient of specific viscosity of the liquid. This shows that the viscosity and the viscosity in different units.
4. Influence of different factors Factors affecting viscosity
: flexible roll diameter, hardness and elastic modulus, the nature of roll, roll speed, roll temperature, environmental temperature and humidity, sample temperature, the ink film thickness, such as ink or link to material on the roll of flexible, elastic roller cleaning process conditions, the nature of the tested samples.
Factors affecting viscosity: viscosity with temperature and species concentration of particles, particle size is closely related to the relationship between air pressure and humidity and little, different measurement methods of measurement accuracy and measurement units are different and can not mutual conversion.
From the above four points, we can see, ink viscosity and viscosity is very different, but both still have contact. Mainly in the viscous fluid viscosity is a measure of the size of the physical quantity, the fluid dynamic viscosity is the inherent physical properties of fluid determined by the amount of viscous fluid whose value is a direct measure of size is also resist shear fluid in motion shear deformation of a measure of strength. The same environmental conditions, viscosity, said viscosity big, and vice versa.
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In our understanding of ink viscosity, viscosity and the quality of the relationship between the subject, followed by discussion of how high-speed rotogravure printing ink viscosity to control the problem.
Ink from organic Solvent , Binders, pigments, Additive To help feed and other components. When these raw materials has been set, the degree of processing methods and the composition has been set, the transfer of good and bad color printing ink viscosity of the main Jiugen about. Proved ink viscosity range (11-24S, using the Zahn viscosity cup No. 3), the greater the viscosity of printing ink, paint the worse the effect of the transfer. Because the role of solvent dissolved resin or additives and additives to give the mobility of pigment is easily distracted. When the ink viscosity is too large, the entire ink system is over-saturated on, pigments and other substances in liquid he sent, not dispersed, but occur in clusters, easily stacked together, so paint can not be successful in and out of mesh. Ink viscosity is too large, paint or simply can not enter inside the mesh, let alone transfer. This is commonly called the phenomenon of blocking version. Therefore, we only allow resin, pigment and organic solvent, such as colloidal system is not in the over-saturation, but saturation or saturation, so that paint and other substances which can be well dispersed to form a uniform fine colloidal system This will smooth the paint out of the mesh, the problem can be resolved. Some ink manufacturers recommended ink viscosity in the 15-18S (Zahn viscosity cup No. 3) between. However, in practice, particularly in gravure printing machine (printing speed in 100-260m/min), in order to ensure the transfer of good results, but can print a long time, improve efficiency, ink viscosity is usually in the 11-15S (Zahn viscosity cup No. 3) looking for their ideal points between.
In plastic gravure printing, it is also often dirty version of the problem. The phenomenon of roller printing surface will be coated with a non-hazy layer of resin (resin entrained paint), and Transfer To the substrate, so that fouling of substrates present sheet, or the performance of the linear fouling. In addition to the dirty version of the root causes of the phenomenon and Scraper Hard and soft degrees Scraper Pressure, the contact angle of blade, the quality of the plate cylinder, the main with the viscosity of printing ink. As mentioned above, the printing viscosity is too large, resin and pigment material flow is poor, did not uniformly dispersed, easily stacked together, the blade and the plate cylinder relative high speed under the squeegee and the plate cylinder is easy to damage, thereby linear prone to fouling. Resin is the same as in the saturated state, a large number of resin coalescence together, and the affinity resin roller, squeegee pressure in the resin will stick tightly
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