Water-based ink pigments (four)

2, red pigment

(1) Pigment Red 58:1 (PR53: 1, C word gold red)

With isopropyl alcohol ink, PH = 8, the lowest viscosity of the ink, the highest color intensity. The pH value of its performance year is not big. After storage at 50° C., the viscosity value increases and the color intensity decreases, as shown in FIGS. 16 and 17 . In general, the pigment has a high viscosity value in water-based ink systems, has poor stability, and has the disadvantage of losing the red light. It is recommended to use PO46, preferably PR70 instead.

(2) Pigment Red 169 (PR169, Rhodamine G)

At lower pH, the viscosity and color intensity of isopropyl alcohol-containing inks are ideal. After 50°C storage, when the PH value is too low, the viscosity of the ink increases rapidly due to flocculation, and the viscosity of the ink quickly decreases when the pH is high. The preferred pH of the pigment is 3.5. See Figure 18, Figure 19.

It is necessary to compare the conditions in which the pH value of the ink changes due to the chemical activity of the pigment in the aqueous ink containing isopropyl alcohol after storage at 50°C.

We clearly see that PB61 caused the greatest drop in the pH value of the ink, and the color change was also large. Like pure waterborne acrylic binders, PB15 and PR53:1 cause a small decrease in the pH of the ink. PR169 and PB1 also cause the pH to decrease to a lesser degree than PB61.

(3) Pigment Red 57:1 (PR57:1, Magenta 6B)

The pigment is used as a three-color magenta color for footprint inks, but when used in water-based inks, there are many problems, for example, yellowing of hue, poor flowability, and easy to gel or thicken the ink. It is generally believed that this is because the free calcium reacts with the resin acid to form an insoluble calcium salt, resulting in precipitation and increased viscosity.

The magenta color of water-based ink can be obtained by color matching. For example, PR49Ba, PR48Ba, and PR53Ba can be combined with PR169. When PR49Ba and PR169 are mixed at a ratio of 5:5:4:5, PR57:1 hue can be obtained, and the color intensity is 10% lower than PR57:1. Around the time when PR48Ba, PR53Ba, and PR169 were mixed, the color intensities were 13% and 16% lower, respectively. See Figure 21, Figure 22. Take care of PR169 ink system suitable PH value of 8.5.

(4) Quinone Red Pigment

These pigments have no activity in aqueous ink, high stability, and have excellent durability, impermeability and chemical resistance, but the color is not bright enough, the cost is high, and there is thixotropy.