Trend of Toluene-free Printing of Intaglio Printing Inks (Chinese)

3. Environmental measures for gravure ink

3.1 Influence of Solvents on the Environment

As mentioned above, since the Labor Safety and Health Act and the PL Act were implemented in 1995, it was expected that no toluene ink would be introduced. Toluene-free inks, which can be used in existing printing equipment, are consistent with the needs of the market and are now rapidly gaining popularity. The gravure ink solvent formulation is generally used by combining various solvents into a mixed solvent according to requirements such as solubility, drying property, cost, and the like. The characteristics and toxicity of the main organic solvents used for gravure inks are shown in Table 2. Although organic solvents that are carcinogenic are not used, some of them cause symptoms such as central nervous system poisoning.

Toluene, one of the solvents listed in Table 2, removes the hygienic property and is in the following respects: 1) the solubility of the resin and additive used in the ink; 2) the drying performance during printing; 3) the ideal solvent in terms of cost . In contrast, MEK (ketone-based) and ethyl acetate (ester-based) solvents perform well and dry quickly. IPA (alcohol-based) has the same drying performance as toluene but has poor solubility. No matter what kind of solvent is higher than toluene in cost.

3.2 Technical problems without toluene

If the toluene in the ink is simply replaced with other solvents, the chemical compatibility and printing of the original ink should be ensured in terms of the stability of the ink and the reproducibility of the tone compared with the original toluene ink. There is difficulty in adaptability, and the plate is prone to fog. As described above, the use of non-toluene solvents results in reduced solubility and slow drying. For the development of non-toluene type inks, it is very important to study the resins and solvents used in the inks. The use of mixed solvents for resins (hydrocarbons, ketones, esters, alcohols) should be such that they have the same solubility as toluene. In addition, the solvent composition should be such that the toluene solvent has the same drying rate. In addition to careful selection of solvents in hydrocarbons, ketones, systems, and alcohols, various solvents must also be considered. The volatilization rate and the solvent balance during printing are not destroyed.