Analysis of four common problems of the hottest so

Analysis of four common problems of solvent based inks

one of the problems: in gravure solvent based ink printing, what is the reason for causing dirty plates (fog in the non graphic part of the gravure plate roller)

in gravure printing, the cause of dirty plates is the ink transfer of the doctor blade, specifically, the ink in the non graphic part is not scraped clean during the scraping process, and the ink in the blank part is not scraped clean mainly due to the problems of machinery and ink composition

mechanical factors: the first reason is that the doctor blade is severely worn. During the normal use of the doctor blade, it will eventually be worn. To solve this problem, you can check the direction of the doctor blade along the gravure cylinder to ensure that the doctor blade is evenly pressed on the gravure cylinder. At the same time, make sure that the doctor blade itself has no wear points and dirty spots, which will affect the ink scraping effect of the doctor blade. If these problems occur, it is best to replace the doctor blade; The second reason is that if the surface of the copper coating and chromium coating of the gravure cylinder is rough, it will also lead to the unclean scraping of the doctor blade. Sometimes changing the angle of the doctor blade can solve this problem. Fake or adjust the doctor blade can not overcome the roughness on the gravure roller, so the plate roller should be polished

ink component factors: if there is a need to change the doctor blade frequently in the production process, it is likely that the pigment in the ink has strong abrasiveness. Consider whether we should work closely with our partners in the industry and research field to change another kind of ink. In addition, improper or excessive use of solvent in the ink will cause the pigment in the ink to flocculate, which will leave the pigment under the doctor blade, resulting in dirty version or wear of the doctor blade

the lubrication performance of ink is also a reason for dirty version. The lubricity of the ink is related to the resin in the ink component. Some gravure ink manufacturers will add a small amount of Dark asphalt to the ink component to improve the ink scraping performance

question 2: please explain the reason why the viscosity of solvent based liquid ink increases and gels? What is the relationship between pigments and this problem

generally speaking, the phenomenon of viscosity increase of solvent based liquid ink is due to the insufficient adsorption of resin on the surface of pigment particles. If the polymer resin is not completely adsorbed on the surface of the pigment particle crystal, the pigment particle surface without adsorption resin is used to pack perishable fresh food noodles, which will aggregate with each other and form flocculation

from a technical point of view, the pigment surface is not completely surrounded by resin, and adsorption does not exist in isolation, but will make the solvent adsorb on the surface of pigment particles. Although the solvent can sometimes wet the pigment, the dispersion of the solvent to the pigment cannot be in a stable position. Therefore, there is a solvent instead of polymer resin surrounding the adsorbed color, and there is no need to worry about the surface of prosthetic material particles. With the passage of time, the surface of pigment particles. With the passage of time, the pigment particles flocculate slowly, and the final result is that the fluidity of the ink changes

theoretically, the solution to the problem of solvent adsorption of pigment particles is to use a resin with high affinity with pigment particles, so that the affinity between the solvent and the surface of pigment particles is lower than that between the resin and pigment particles. Similarly, if the polymer resin has good solubility in the solvent mixing system, the flocculation probability of pigment particles can be reduced to the minimum, because the solvent/resin has better binding than the pigment/solvent

question 3: how to improve the adhesion of nitrocellulose (NC)/polyurethane (PU) solvent based ink

there are several different ways to solve this problem. First, you can add titanate or zirconium aluminate additives to the ink, and these additives can cooperate with the oxygen-containing groups on the surface of the substrate, which can improve the adhesion between the ink and the substrate. The second solution is to modify nitrocellulose/polyurethane resin with polychlorinated olefins. The problem to be considered is the ratio of nitrocellulose/polyurethane in the formula of nitrocellulose/polyurethane solvent gondola

obviously, nitrocellulose resin is hard and brittle, and there is not enough plasticity. Therefore, solvent based inks using nitrocellulose resin as binder lack toughness and elasticity, and the adhesion is very poor. Adding polyurethane to the continuous feed can effectively improve the plasticity of nitrocellulose and the adhesion of ink, and the cost of ink is also increased. Adding titanate (DOP, BBP, DBP) or benzoate can soften nitrocellulose, and the price is also cheaper. However, some titanates are only limited to some food packaging and printing applications

question 4: how to measure the surface tension of gravure solvent based inks? How does the surface tension of ink affect the printability and composite strength

if the surface tension of the ink needs to be measured in the work, we can use a tensiometer to measure it. However, this measurement method can only measure the static surface tension of the ink (the surface tension of the ink at rest). However, the ink will definitely receive dynamic force on the printing machine. Therefore, the really effective surface tension should be the surface tension measured when the dynamic force exists. Sometimes the dynamic surface tension is not easy to measure

there is a kind of bubble pressure tensiometer that measures the surface tension under the action of dynamic force, but these devices are relatively expensive and are generally not used in ink laboratories

when printing with water-based ink, surface tension is an important problem. This is because the surface tension of the water-based ink is higher than the surface energy of the substrate. In these water-based inks, some additives are often added to reduce the surface tension of the ink, so that the water-based ink can be well wetted on the substrate surface 3

for any specific water-based ink formula, the main role of surface tension is to affect the leveling of ink on the substrate surface. Solvent based inks generally have low surface tension, so they can be well wetted on the surface of a variety of substrates. However, good wettability does not mean good adhesion, but good printing quality. The adhesion between the resin component in the ink and the substrate surface is the primary factor affecting the adhesion and composite strength of the ink. The composite strength is also related to the adhesion of the ink itself. The interweaving effect of polymer resin in ink and the physical effect between various raw materials in ink are the basis for ink to resist the stripping effect of composite film. Therefore, the structure (linear molecule or molecule containing branched chain) and molecular weight of resin molecules will also improve the adhesion of ink, so the composite bonding strength will increase