Water Based Inks (3)

Fourth, the application of pigments in water-based ink

A company has studied the effect of commonly used color pigments in aqueous acrylic systems, pH value and isopropyl alcohol on ink viscosity, color intensity, and storage stability. The amount of pigment in the ink was 8%. The viscosity was measured in a #4 cup. The storage stability was determined by measuring the change in viscosity after the ink was sealed in a bottle and allowed to stand at 50C for one week.

1, blue pigment

(1) Pigment Blue 15 (PB15, Phthalocyanine Blue)

First, naked phthalocyanine blue (PB15:3) and deflocculating hydrophilic phthalocyanine blue (PB15:4) are discussed. As can be seen from Figure 8, if the ink does not contain isopropanol, the viscosity values ​​at different pH values ​​are not much different, except that the hydrophilic phthalocyanine blue has a slightly increased viscosity value after storage at 50°C. After adding isopropanol, the situation is very different. As shown in Fig. 9, the viscosity value increases with the increase of PH value, the viscosity value increases after storage at 50°C, and it shows the worst at pH=9. Storage stability.

If the fluidity of the ink is poor due to the good dispersion of the pigment, ie, the high color intensity, the higher viscosity value may not be considered as a disadvantage. Because, if the same viscosity value is reached, as long as it is diluted to the same color intensity, the result is reduced cost. As can be seen from Figure 10, the hydrophilic phthalocyanine blue has a slightly higher color intensity and is not affected by the pH value. According to Fig. 11, when the pH values ​​are 8 and 8.5, the color intensities of the two pigments are the same, and when the pH is in the higher range, the hydrophilic phthalocyanine blue shows superiority. After storage at 50°C, the color intensity of the two pigments was almost unchanged.

(2) Pigment Blue 1 (PB1)

The ink containing no isopropanol has a low viscosity value and is not affected by the pH value. There is no change in the viscosity value after storage and the color strength is low.

For aqueous inks containing isopropanol, the viscosity value increases with the increase of PH value, and the viscosity value is the highest when PH=9.5, and the storage stability is not good when the PH value is between 8.5 and 9. The color intensity is higher. When the pH is 8.5, the highest color intensity is achieved. After 50° C. storage, the color intensity of the ink does not change much, as shown in FIGS. 12 and 13 .

It can be concluded that the pigment has the best flowability, high color intensity and color definition at pH = 8.5.

(3) Pigment Blue 61 (PB, 61 Light Blue)

Aqueous inks without isopropanol have similar viscosity, color strength, and storage stability as Pigment Blue 1.

In inks containing isopropanol, the highest color intensity and lower viscosity values ​​are obtained at the lowest pH, and the color intensity decreases with increasing pH. PH value of 8.5 to 9.5, storage stability is not good, after 50 °C storage, the color intensity decreased by more than 10%. See Figure 14 and Figure 15. It can be considered that the pigment has a good performance in the range of PH=8 to 8.5.