The most popular packaging printing ink scaling ha

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The harm and prevention of ink scaling in packaging and printing (I)

I. packaging and printing "he added that the measures taken after ink scaling are known to all. When the ink in the ink bucket forms a layer of film due to the drying of the surface during the printing process, either place a mixing device, or simply pour out the ink. Otherwise, the film will adhere to the roller, resulting in uneven layout, This leads to the contamination of random knife marks on printed products. The reason is that the ink industry tends to: (1) the ink dries too fast; (2) Poor ink fluidity; (3) The ink deposit has dried. However, it is unknown that this phenomenon is caused by the evaporation, evaporation, or oxidation drying gradient of the ink system, while the printing industry believes that: the ink barrel or ink bucket structure is not good, resulting in a stagnant retention part, and the air leaked from the dryer dries the surface of the ink or the hot air blows the ink into the ink bucket. Although there are different opinions, around the emergence of this phenomenon, printing operators generally adopt the following treatment methods: (1) do not use ink that dries too fast; (2) Add medium and slow drying solvent; (3) Replace the deteriorated ink (i.e. from poor liquidity to excellent liquidity); (4) Keep stirring in the ink bucket; (5) A closed top cover is arranged on the ink fountain; (6) Adjust the hot blowing angle. Generally, people with printing experience and common sense, when the drying speed is too fast, or the ink concentration is too light, or the flow is poor, or the ink thixotropy is large, or the ink is electrostatic, they will adopt the method of speeding up the printing machine speed, which not only prevents the ink from drying on the printing plate in advance, but also overcomes the crust formed by the film-forming of the packaging printing ink, and eliminates the speckle fault of the graphics and texts

second, stabilizing the film-forming quality of packaging and printing ink can control the free radical polymerization, drying or solvent volatilization of packaging and printing ink film, as well as the active role of oxidation, so as to achieve the purpose of preventing scaling. However, this control function must be based on needs, which will not affect the drying rate of the film-forming of printed graphics and texts, nor the performance and quality of the ink products. This is the minimum standard for ink manufacturing. In order to achieve this goal, the author suggests the following three methods: Method 1: adding antioxidant and retarder. In the printing ink system, the function of adding antioxidants or retarders is to prevent the production of free radicals in the film-forming process of packaging and printing graphics and texts, so as to interrupt the oxidation and volatile polymerization of the ink film. Once the solvent volatilizes in a very short time, the oxidation process of the oil will also be reduced, and the free radicals produced by the ink will continue to polymerize into a film (such as the product series of Tianjin Li biochemical factory). Method 2: add oxygen isolating agent. Liquid paraffin, called oxygen isolating agent, is added to the packaging and printing ink, and the steam generated is filled between the ink barrels, cans and boxes to form an oxygen isolating layer (film), which effectively prevents the solvent in the ink system from being easily volatilized by clicking the "TXT format save" or "RTF format save" button due to vapor pressure. Method 3: add complexing agent. The use of oxime compounds (methyl ethyl ketone oxime, butyraldehyde oxime, cyclohexanone oxime p-hydroquinone, etc.) can help business users and consumer groups control the activity of other drying agents in the ink system during the purchase and use process, and play a role in delaying or preventing crusting. For a long time, it has been more than 50 years since anti scaling agents (i.e., polymerization inhibitors) were added to packaging and printing inks. In the past 40 years, phenols have been mostly used, while benzoic acid has been used in ink, which is both time-saving and labor-saving compared with the first choice of solvent with high boiling point for covering. Because the phenolic compound itself is a proton donor, it can produce peroxidation free radical reaction in the process of oxidation reaction, generate ROOH, form a stable anti oxygen free radical at the same time, capture active free radicals, and terminate the reaction of oxidative polymerization - preventing the scaling of printing ink. With the development of science and technology, in recent years, people have used oxime compounds as ink anti scaling agents, and found that butyraldehyde and methyl ethyl ketone oxime have the best effect on preventing ink scaling. Some ink manufacturers and packaging and printing operators believe that the anti gel effect of oxime compounds has exceeded that of traditional phenolic compounds. In the 1980s, China successfully developed methyl ethyl ketone oxime anti scaling agent for the first time. After the advent of butyraldehyde oxime, the application and effect of our country have reached the world advanced level

III. application scope and precautions of anti scaling agent oxidation of packaging and printing ink, especially the volatile speed of solvent, the oil of modified resin, the amount of pigments, fillers, driers used, the storage environment temperature and humidity of finished ink products have a certain impact on the scaling (gel) of ink, so the above factors must be considered when using anti scaling agent (gel), At the same time, we should also pay attention to the basic situation of seven aspects, such as the amount of addition: 1. The amount of addition. Generally, it is calculated according to the ink material (because the main component of the crust is the main raw material of the ink) or the total amount of packaging and printing ink, and at the same time, it is also considered to be affected by other components

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