Use water-based ink printing, why the sewer will have impurities in the ink precipitation?

(1) The proportion of water-based ink is generally greater than the proportion of water. When the machine is washed, a small amount of ink is flushed into the sewer, accumulated for a long period of time, and precipitates form in the sewer.

(2) The chemical nature of the aqueous ink is weakly alkaline, ie the PH value is between 8-10. Most of the printing companies use the pipeline water (tap water) when diluting the ink and cleaning the machine. Because the pipeline water contains a certain amount of calcium and magnesium ions, over time, the hydroxide (OH) ions in the aqueous ink and the calcium in the water , Magnesium (Ca, Mg) ions form a new chemical substance (CaOH2, MgOH2, etc.). These chemicals are themselves precipitated substances that cause impurities to precipitate in the sewer. (Mr. Sun Zhiyong, Technical Department, Solvent and Ink Division, Tianjin Toyo Ink Co., Ltd.)