How to solve the deviation of the printed product caused by the expansion of the blanket after cleaning?

The surface of the offset printing blanket is composed of non-polar synthetic rubber. It is best to be able to absorb the ink to the maximum and the moisture to the minimum during the printing process. However, in the printing process, due to the role of physical adsorption, it will gradually accumulate on the surface of the blanket to form a stain layer, mainly composed of paper coating particles, plant fibers and pigment particles in ink. Since these materials are mostly polar substances, the stain layer reduces the lipophilicity and hydrophilicity of the blanket, so that the small dots on the printing plate cannot be transferred to the substrate through the blanket, resulting in the loss of fine dots. White spots appear, which seriously affect the printing quality. On the other hand, the enhanced hydrophilicity causes the blanket to absorb more wetting fluid from the non-graphic part of the printing plate and transfer it to the paper, which causes the paper to elongate and cause overprinting. In addition, if the stain layer is too thick and too hard, it will cause a large plastic deformation of the rubber layout part, destroy the uniformity of the thickness of the rubber cloth, and cause a phenomenon of insufficient printing pressure locally.

Since the stain layer on the blanket contains both polar paper powder, paper wool, etc., and non-polar ink binder solvent, according to the principle of similar miscibility, organic solvents and water should be mixed for blanket cleaning. However, among them, organic solvents with relatively fast volatilization speed, kerosene or other organic solvents with low volatilization rate are liable to cause swelling and aging of the blanket, and foaming, delamination, and expansion of the blanket can occur.

Once the blanket has undergone significant expansion, its various printing performance indicators will drop sharply. The decline in the performance of the blanket will directly affect the effect of the printed matter. For example, the thickness of the blanket will change due to the expansion of the blanket, which will increase the printing pressure and increase the dots. Difficult; the elasticity of the blanket after expansion decreases, resulting in poor ink transferability and reduced printing uniformity.

In fact, blanket cleaning during offset printing is inevitable and necessary. But the solvents such as gasoline, kerosene, blanket cleaning agent, blanket reducing agent, etc., which are commonly used for blanket cleaning, will cause excessive expansion of the blanket when used improperly. Therefore, in the printing process, the stain accumulation on the surface of the blanket and the requirements of different printing jobs should be considered. Clean the blankets frequently to ensure the clarity of the printed graphics and extend the life of the blankets. [next]

The fundamental method to solve the expansion of the blanket after cleaning is to use high-quality blanket cleaner. This cleaning agent specially developed for blankets is not only composed of highly volatile solvents, but also a new type of cleaning agent optimized for the composition of stain materials accumulated on the blankets, mainly caused by the chemical damage to the offset blankets. The composition of organic solvent and surfactant that can generate a relatively stable water-in-oil emulsion can reduce its swelling effect on the blanket to a minimum. The blanket cleaning agent developed according to the chemical rule of "similar chemical structure is similar to each other", when it comes into contact with the emulsified ink remaining on the blanket, the organic solvent will dissolve the binder and other organic resins in the ink. Good pigment particles and hydrophilic paper powder and paper wool mixed into the ink take down, and can dissolve and remove the inorganic and colloidal compounds of the wetting liquid remaining in the emulsified ink for offset printing. Therefore, the surface of the blanket after washing is clean and free of traces of pigment, and there will be no "crystallization" or "white dirt". It can quickly and effectively remove the stains on the blanket, restore the surface characteristics of the rubber, and has extremely low side effects of expansion, which can extend the service life of the rubber.

Therefore, the selection of high-quality blanket cleaning agents can achieve more than 95% cleanliness of organic and inorganic compounds. At the same time, it has good adaptability to blankets and the expansion rate generated is not higher than 2%. In addition, the theoretical recovery rate of the recovered ink cleaning agent as clean ink cleaning can reach more than 95%, and the actual recovery rate is more than 85%, which not only avoids the pollution of the cleaning agent to the environment, but also saves related production costs.

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