In packaging During the printing process, there are occasional problems of streaks or light colors on the printed products. Many people in the industry call it “no ink or ink roll offâ€. This is mainly because the pigments and fillers in the ink system swell, resulting in ink. Due to the overall gelation. Once the ink gels, it is also more troublesome to handle. Some use the ink in the mixing fountain or the automatic mixer in the ink fountain to solve the problem. Some add medium and high viscosity varnish or thinner to adjust. Ink, and some directly pour off the gelled ink and replace it with a new one. These practices not only have certain limitations, but also cause serious waste. Therefore, the problem of ink gelation has been plaguing the industry. Causes of ink gelation Oily (oxidatively dry and osmotic drying) inks used in the packaging and printing industry often have gelling problems, and occasionally such problems occur in solvent-based (volatile dry-type) and water-based inks. The reason is mainly related to the ink production process. For example, the first or the addition of the drier may cause the ink to gel. After detailed analysis, the author believes that there are mainly six reasons for the gelation of ink. (1) The molecular weight of the resin in the ink system is too large, so that the viscosity of the ink is too high. (2) The resin binder having a low viscosity in the ink is excessively contained. (3) The acid value of the ink system is too high. (4) The pigment or filler in the ink has a certain basicity. (5) The amount of desiccant in the ink is too large or the order of addition is improper. (6) A certain type of solvent in the ink system, especially the content of fast drying solvent. The first two of the above six reasons belong to the physics category. It is easy for an experienced ink manufacturer or packaging and printing operator to take these two points into consideration and take measures to prevent ink gelation. Then the four reasons belong to the category of chemical reaction. When I explored the following four reasons, I found that the application of auxiliary additives in the ink manufacturing process is too high, the temperature of the dispersion process is too high, and the solvent volatilization is too fast, which is more likely to cause ink gelation. In particular, improper application of auxiliary additives is the easiest to become the "truth" of ink gelation. When the stoichiometric concentration of a substance in the ink is large to a certain value (strictly speaking, it can be a narrow concentration range), the macroscopic properties of the ink suddenly change. From a microscopic point of view, at this time, the active molecules of the ink system begin to associate, forming aggregates of different sizes of colloidal particles. Such aggregates are called "micelles or micelles", also known as "association colloids". ". An important characteristic of the micelles is their solubilization, which greatly enhances the solubility of the originally insoluble or slightly soluble substances. This is called swelling, and further develops into ink gelation. In addition, the pH of the pigments and fillers used in the ink can also have a direct effect on ink gelation. I have studied the cause of gelation of rosin resin with a molecular weight of only 330 in the production of solvent-based inks. It has been found that the acid value of strong acid pigment carbon black pigment and rosin has a great influence on ink gelation. Since the acidic ion is electrophilic, it is an electron acceptor (proton donor), and the basic ion is nucleophilic, which is an electron donor (proton acceptor). Among the raw materials for the production of inks, there are so-called amphoteric solvents and resins, among which are proton donors and proton acceptors (water, alcohol, carboxylic acid, nitrocellulose, etc.), and hydrogen is not formed. Bonded aliphatic hydrocarbon solvents and neutral pigments and amphoteric pigments, all of which are directly related to ink gelation. When the acidity and alkalinity of the pigment in the ink are not compatible with the acidity and alkalinity of other fillers, the ink is prone to gelation problems. In this regard, we can combine the acid-base characteristics of pigments and fillers to balance the acid-base phase in the ink component, or add a suitable solvent to make up for it. In addition, the drier in the ink system also affects the viscosity, swelling, etc. of the ink during storage. If the high viscosity alkyd resin and the basic pigment zinc oxide are ground together in the presence of a drier, the ink will be gelled. This is mainly due to the reaction of free fatty acids and basic pigments during thermal processing. Therefore, when using high-viscosity ink raw materials, drier containing lead, cobalt and manganese should not be added during the grinding process. If such drier is used inadvertently, there are certain remedies for adding 1% benzoic acid. This can significantly reduce the tendency of ink gelation, but this method is not recommended as a solution. It is worth noting that the drier will accelerate the sedimentation of the pigment in the ink (in the storage state), so it is forbidden to add a drier before the pigment is ground to prevent the ink from sinking during storage. Ink gelation solutions In response to the problem of ink gelation, the industry has proposed a number of solutions, summed up the following four. (1) The addition of a metal salt of naphthoic acid to the ink is the most common method for solving the problem of ink gelation. (2) When the ink is too thick or gelatinized due to excessive polymerization of the binder, a solvent such as an aliphatic hydrocarbon, an ester or a ketone is added for dilution. (3) For the gelled ink which is reacted into soap, rosin is added thereto and dissolved in linoleum, and the acid is gelled by using a high acid value substance. (4) For the problem of gelation of aqueous inks, it is necessary to add inorganic salts for control. It is not difficult to see that the above solutions are all passive operations after ink gelation, which not only delays the production process, but also greatly increases the production cost of packaging and printing enterprises. To this end, the author has found a feasible solution according to the principle of ink gelation, that is, starting from the ink formulation structure and preventing from the production stage to prevent gelation during the storage and use. The author selects the best anti-expansion gel from many ink additives. Through experimental demonstration, the author recommends the improved phosphate ester coupling agent produced by Yizheng Tianyang Chemical Co., Ltd., which not only has excellent dispersion. Performance, can also make the swelled, gelatinized ink "return to life", in the printing process, only need to add 3% ~ 5% anti-swelling glue in the gelled ink, can make the ink viscosity return , the state is restored. After repeated research, I found that adding a small amount of anti-swelling gel (1.5% to 2.5% of pigment content) in the ink formulation can greatly improve the dispersibility of the pigment and prevent the ink from appearing during production, storage and printing. It swells, gels, and precipitates, and at the same time greatly enhances the degree of branching of the ink, thereby improving the adhesion fastness of the ink film. More importantly, it also reduces the baking temperature and the amount of blowing, which significantly reduces the energy consumption of packaging and printing companies. (Editor: Pang Junqi) The above content is reproduced in the " Printing Technology " official WeChat (Printech1957), authorized by the company to publish, copyright, piracy will be investigated! Spark needle cartridge are New Needle Cartridge disposable single-use tattoo needle cartridges that allow tattoo Classic Tattoo Needle Cartridge , New Tattoo Needle Cartridge ,Ez Tattoo needle cartridge , Cheyenne Hawk Tattoo needle cartridge , T-tech needle cartridge , Elite Tattoo needle cartridge Amztatto Supply Co., Ltd. , https://www.amztatto.com
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