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[technical] gravure ink and knife wire fault analysis
Source: Date:2016-8-25
A knife is one of the common quality fault printing difficult to avoid. The gravure printing ink is very short, the scraper to imprint the distance is generally not more than 1/4 of the circumference of the roll. If the process is considered, the blade position will be raised to the point near the impression, the distance will be shorter. This short of monlchamus Road, the risk is that if a foreign body are embedded on the blade, not to the wettability of the ink itself leveling the foreign body to pull out of the wire, thread will transfer to printing material, wire cutter.
1, solvent based gravure ink
Gravure printing, the use of solvent based inks and there is no way to avoid the cause of wire cutter, in addition to environmental factors caused by foreign bodies embedded in the outer scraper, the main reason is to solvent based inks used mixed solvent solubility fluctuations.
Gravure printing in the mixed solvent generally from 2 to 3 kinds of solvent composition, the core of the formula, first of all to ensure solubility of mixed solvents on resin (solute). The three elements of the solubility of resin include: polar similarity and similar principle, the principle of similar solubility parameters and the principle of solvation. A good mixture of solvent formulations, generally in accordance with the three principles. However, due to the solubility parameter of the solvent mixture calculation with solvent volume parameters, when mixed solvent after the volatile period of time, the volume of the solvent ratio will be big changes, the solubility parameter of solvent mixture will big changes. As long as the solubility parameter of the fluctuation in + (15% ~ 20%), the solubility of the resin is guaranteed, but if exceed the limit value has dissolved resin may to coalesce into larger particles, the formation of soluble fault. In this condition, if the particles embedded scraper, wire cutter failure is inevitable.
Gravure printing production line evaluation of a new ink is easy to wire cutter and method used is often let version and idling more than half an hour, and then re printing, the intention is to wait for the solvent type ink mixing ratio and volatile than serious inconsistent to assess the risks of coagulation of ink particles. This method is very scientific, but in the use of this method at the same time, there are many people who are from the theoretical point of view of mixed solvent solubility to think, it is worth to doubt.
2, water-based gravure ink
Water based gravure ink by a mixed solvent, theory does not exist because of the mixing ratio and volatilization is caused by dissolution of volatility risk. But the reality is, water-based gravure ink printing knife is inevitable. In fact, cause there is a water-based gravure ink dissolved Volatility: is alkaline substances in water based gravure ink changes caused by the change of pH value, thereby causing changes in solubility; the second is the matching of water based gravure ink water solution and aqueous emulsion, the mixture will cause resin insoluble.
Water emulsion paste with solubility and dry with good or bad, directly affect the solubility and dispersion of water-based ink. Some brands of water-based ink, safe storage period only six months, more than six months is likely to produce precipitation, hierarchical, even re mixing, it is difficult to regeneration. In fact, this is the solubility problem, namely paste with water emulsion with problems. The water solubility of ink, water-based ink and gravure printing using the transfer mechanism, will cause the knife line fault.
There is a phenomenon worthy of attention: if only using the aqueous solution composed of water-based ink for gravure printing, the printing process of wire cutter will be greatly reduced. This phenomenon reflects the fluctuation of water-based ink dissolved in aqueous solution and the aqueous emulsion does not match the form. But in the film gravure, the adhesion of the ink and the ink film resistance can not be separated from water emulsion, so as avoid wire cutter without adding the aqueous emulsion is not realistic. Water based ink must be added to the water emulsion, but added a water-based emulsion and can not ensure the stability of the solubility, which caused the current embarrassment of water-based ink manufacturers.
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