Performance requirements that ink cleaners should meet in offset printing
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It is often necessary to clean the ink on the ink roller and blanket during the flip printing process (after color change or shutdown). To remove the ink well, the ingredients of the offset printing ink should first be solved.
Generally, the upper components of the offset printing ink are: solid resin 48%, liquid resin 6%, colloidal oil 20%, wax 5%, aluminum carbonate 2%, pigment 15%.
The cleaning process actually uses a suitable solvent to dissolve the resin components for the purpose of removal.
The resin in the printing ink is generally a phenolic resin, and the commonly used resins are rosin-modified phenolic resins, alkyd resins and polyurethane alkyd resins. To remove them, find a solvent that will dissolve these resins. According to the principle of similar compatibility (ie, the solvent of a polar gene dissolves a substance with a polar gene, the non-polar solvent dissolves a non-polar substance) and the solubility parameter theory (for a non-polar molecular system, usually the dissolution of the polymer) For example, the solubility parameters of the solvent and the solute are as close as possible to facilitate dissolution. A solvent can be found. The solvent should have the following properties:
1. Has a high solubility.
2. Faster evaporation rate.
3. Strong permeability.
4. Good adsorption wettability.
5. It is harmless to the human body and is used by the party.
6. There is almost no corrosion to the blanket and the ink roller.
7. Low cost.
The solubility parameter of the phenolic resin is between 8 and 11.5, and the solubility parameter of the main solvent in the cleaning agent should also be in this range. The solubility of ketones, xylenes, diethylene glycol, valerolactone, and the like is in this range, and thus it is preferred to select one or two as a solvent. It has been tested and combined with valerolactone and dimethicone as a common solvent for inks and photographic adhesives, and its solubility is good. Therefore, the mixed components of the two are selected as solvents; hydrocarbon solvents such as n-g can also be selected. Solvents such as alkane and high-boiling kerosene adjust the volatilization rate of the whole solution; since the binary lower halogenated hydrocarbons, such as 1,1,1-trichloroethane, are highly permeable, they can act as penetrants for cleaning agents; Surfactant can improve the adsorption, wetting and dispersion properties of the solution. OP-10 is a nonionic surfactant with easy dispersion and good hydrophilic and oleophobic ability. It can be used together with anionic surfactants for oil/water. Type emulsifier penetrant. Since it has a higher solubility in cold water than hot water, it is preferred as an emulsifier. The preferred formulation of the cleaning agent can be as follows: solvent: 45% solubilizer: 30% penetrant 5% diluent: 15% emulsifier: 5%
However, the above cleaning agent has an obvious disadvantage, that is, the solvent content is high, the volatilization in the printing workshop is very serious, and the printing environment and the health of the worker are seriously affected, and the cost is high. Therefore, many printing plants simply use gasoline as a cleaning agent. Is this inappropriate? Obviously, it is definitely wrong to sacrifice the environment and the health of workers in exchange for the reduction in printing costs. European and American countries passed environmental protection laws (VOC laws) around the 1990s. According to the law, all soils using organic solvents must meet the following requirements:
1. There should be no smell of organic solvents outside the job shop.
2. The concentration of volatile substances in the job shop must be lower than:
1) Volatile organic solvent 50 m / m 3
2) Carbon monoxide 100 mg/m3
3) Nitric oxide 100 mg / m3.