Packaging Printing Ink Hazard and Prevention (Part One)

First, the measures taken after the crust printing of packaging printing ink We all know that when the ink in the ink fountain in the printing process forms a layer of film due to the dryness of the surface layer, either a stirring device is placed or the ink is simply dropped, otherwise The film will adhere to the roller, and as a result, the layout will be uneven, resulting in contamination of the printed product. The reason for this is that the ink industry tends to: (1) the ink dries too quickly; (2) the ink is poorly fluid; (3) the ink has dried out. But I do not know this phenomenon is caused by the evaporation of the ink system, or evaporation, or oxidation drying gradient caused by large, while the printing industry believes: ink ink tank or ink fountain structure is not good, resulting in a non-flowing retention part from the dry The air leaked from the machine dried the surface of the ink or caused by the ink blown into the ink fountain. Although there are different opinions, but the emergence of this phenomenon, the printing operators generally use the following treatment methods: (1) can not use fast drying ink; (2) add medium and slow dry solvents; (3) replace the deterioration of the Ink (i.e. from poor flowability to excellent fluidity); (4) Stirring in the ink fountain; (5) Setting a closed top cover on the ink fountain; (6) Adjusting the hot air blow angle. Persons who have general experience in printing experience, when the dry speed is too fast, or the ink concentration is too light, or the flow is poor, or the ink is thixotropic, or the ink is electrostatically charged, the method of adjusting the speed of the printing machine will be adopted to prevent the ink. The dried knots are formed on the printing plate earlier, and the crust formed by the film forming the packaging printing ink is overcome, eliminating the speckle failure of the graphic.

Second, the stable packaging printing ink graphic film quality can control the packaging and printing ink ink film free radical polymerization, drying or solvent evaporation, and oxidation of the active role, can achieve the purpose of preventing crust. However, this control function must be based on the need, neither affecting the drying rate of the film-printing graphics, nor the performance and quality of the ink product. This is the minimum standard for ink manufacturing. In order to achieve this goal, the author proposes to adopt the following three methods: Method 1: Add antioxidant and retarder. In the printing ink system, the function of adding an antioxidant or a retarder is to prevent free radicals from being generated in the film-forming process of packaging and printing, thereby interrupting the oxidation and volatilization polymerization of the ink film. Once the solvent evaporates in a very short time, the oxidation process of the oil is also reduced, and the free radicals produced by the ink will continue to polymerize into a film (such as the Tianjin Liexue Chemical Factory product series). Method two: Add oxygen barrier agent. A liquid paraffin known as an oxygen barrier agent is added to the packaging printing ink, and the generated vapor is filled between the ink drum, the can, and the box to form an oxygen barrier layer (film), thereby effectively preventing the vapor pressure. The solvent in the ink system is very volatile. Method 3: Add complexing agent. The use of anthraquinone compounds (methyl ethyl ketone oxime, butyraldehyde oxime, cyclohexanone oxime, hydroquinone, etc.) controls the activity of the drier activator in the ink system and serves to retard or prevent crusting. For a long time, packaging printing inks have added anti-skinning agents (ie, polymerization inhibitors) for more than 50 years. Most of the past 40 years have used phenols, while in inks, benzoic acid has been used, which is higher than the earliest selection. The boiling point solvent cover is both time-saving and labor-saving. Because the phenolic compound itself is a proton donor, it can produce a peroxide radical reaction during the oxidation reaction, generate ROOH, and at the same time form a stable antioxidant free radical, trap active free radicals, and terminate the reaction of oxidative polymerization - Prevents the crust of the printing ink. With the development of science and technology, in recent years, after the use of anthraquinone compounds as ink anti-skinning agents, it has been found that butyraldehyde and methyl ethyl ketone oxime have the best effect on preventing ink crusting. Some ink manufacturers and packaging printers believe that the anti-gelling effect of terpenoids has surpassed traditional phenolic compounds. In the 1980s, China successfully developed the methyl ethyl ketone oxime anti-skinning agent for the first time. Following the advent of butyraldoxime, China's application and effectiveness have reached the world's advanced level.

Third, the scope and precautions of the application of anti-skinning agent The oxidation of packaging printing ink, especially the solvent volatilization speed, the modified resin oil, the use of pigments, fillers, driers dosage, the finished product storage environment temperature, humidity All factors have a certain influence on the crust (gel) of the ink, so when using the anti-skinning agent (gelling agent), all factors mentioned above must be taken into consideration, and at the same time, attention should also be paid to the amount of addition and the like. The basic situation of the aspects: 1, add the amount. Generally calculated according to the ink material (because the main component of the skin is the main raw material of the ink) or calculated according to the total amount of packaging printing ink, but also taking into account the influence of other components.