Performance Requirements for Ink Cleaning Agents in Offset Printing

During the offset printing process (after a color change or shutdown) it is often necessary to clean the ink on the ink roller and the blanket. To remove the ink very well, first of all, the composition of the offset printing ink should be solved.

Generally speaking, the upper components of the offset printing ink are: 48% solid resin, 6% liquid resin, 20% colloidal oil, 5% wax, 2% aluminum carbonate, and 15% pigment.

The removal process is actually the use of a suitable solvent to dissolve the resin components to achieve the purpose of removal.

The resin in the printing ink is generally a phenolic resin, and commonly used resins include a rosin-modified phenolic resin, an alkyd resin and a polyurethane alkyd resin. To clear them, find the solvent that will dissolve these resins. According to the principle of similar dissolution (that is, a solvent of a polar gene dissolves a substance having a polar gene, a non-polar solvent dissolves a non-polar substance) and a solubility parameter theory (for non-polar molecular systems, usually the dissolution of a polymer For the solvent and solutes, the solubility parameters 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. Harmless to the human body, use the party to make.

6. Basically no corrosion to the blanket and ink roller.

7. Low cost.

The solubility parameters of the phenolic resin are between 8 and 11.5, and the solubility parameters of the main solvent in the cleaning agent should also be in this range. The solubility of ketones, xylenes, diethylene glycol, valerolactone, etc. is in this range, so that one or two of them are selected as the solvent. After testing, using valerolactone and dimethylbenzene as a common solvent for inks and photoresists, the solubility is good, so choose the two components of the mixture as a solvent; you can also choose to use hydrocarbon solvents, such as n-g Alkane, high boiling point kerosene and other solvents adjust the volatilization rate of the entire solution; due to the strong permeability of binary lower halogenated hydrocarbons such as 1,1,1-trichloroethane, they can be used as penetrants for cleaning agents; anions are added. Surfactants improve the wetting and dispersing properties of solutions. OP-10 is a non-ionic surfactant that is easy to disperse and has good hydrophilic oleophobicity. It can be used with an anionic surfactant as oil/water. Emulsifier penetrant. Because its solubility in cold water is greater than in hot water, it is ideal as an emulsifier. The ideal formula for cleaning agents can be as follows: Solvent: 45% Solubilizer: 30% penetrant 5% Thinner: 15% Emulsifier: 5%

However, the above-mentioned cleaning agent has a significant disadvantage in that the amount of the solvent is high, and the volatilization in the printing shop is very serious, which has a serious impact on the printing environment and the health of workers, and the cost is high. Therefore, many printers simply use gasoline as a cleaning agent. Is this inappropriate? Obviously, the decline in printing costs at the expense of the environment and the health of workers is certainly wrong. Before and after the 1990s, European countries and European countries passed the Environmental Protection Law (VOC). According to the provisions of the law, all organic fertility 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/m3

2) Carbon monoxide 100 mg/m3

3) Nitric oxide 100 mg/m3.