Rheological properties and printability of the bes

Rheological properties and printability of water washable waterless ink (Part 2)

(physiology and printability of water washable waterless ink)

continuous fluidity

ordinary waterless ink - the rheological curves of four printing primary color inks (yellow, magenta, cyan, black) used for ordinary non horizontal printing are shown in Figure 1. By observing the viscosity curve (n pairs γ）， We can conclude that these four inks (except perhaps black inks) exhibit the properties of Newtonian fluid at 0.01-10s-1, and then the viscosity decreases at a higher shear rate (>10 s-1). In addition, the shear rate between 10-1000 S-1 will also decrease due to the difference of resin binder in offset printing ink or the chain breaking of polymer chain. Black 2. According to the wire diameter in the parameter table, the curve of clip arc radius r ink decreases after 10 s-1, perhaps because the wettability of pigments in the resin is poor

is almost linear within the whole test range. Each curve conforms to Herschel Bulkley model δ=δ y+K γη， among δ Y is the deformation stress (the minimum stress required to observe the flow), and K is the viscosity coefficient, η Is the scale factor. δ The values of Y are listed in Table 1. be-all δ Y values are all 0（ ×） Measured value at PA. However, when the experimental speed of shear is up to 0.001mm/min ⑴ the rate of 000mm/min is very small, there is no resistance to flow. This feature is extremely important in the process of ink transfer to paper and initial coating. The pigment is evenly distributed in the resin, without friction and resistance, and is fully wetted by the resin. In the whole process, only a small stress is generated in the ink

Figure 1 rheological curve of traditional anhydrous inks (k, C, m, y)

Table 1: stress yield value in Herschel Bulkley model

four color inks δ y（ ×） PA (for ordinary ink) δ Y (PA) (for class a ink)

k 17500 131

c 5.9 448

m 0.11 513

y 5.2 785

low gloss water-based, washable anhydrous ink (type A) - the flow curve of low gloss washable ink a for four printing primary colors is shown in Figure 2. Compare the viscosity curve with the shear rate in the range of 0.01-10 s-1. From Figure 1, it can be seen that there is no Newtonian stagnation in ordinary anhydrous printing ink. Suppose that the stagnation phenomenon occurs because the selected resin does not infiltrate the pigment well, so it is necessary to find a new resin binder to improve the infiltration of the pigment, so as to improve the smoothness and gloss of the ink on the print. However, the shear bands of the two figures are very narrow at higher shear rates (>10s-1)

in the stress shear rate curve, it conforms to Herschel Bulkley's model δ=δ y+ K γη When the shear rate is not high (from 131pa black ink to 785pa magenta ink), it will produce a large yield stress. These yield stresses must be overcome in order to obtain high smoothness in printed matter. This kind of stress is not 6. The fasteners of the electro-hydraulic servo universal testing machine should be locked regularly: the vibration after the specimen is broken will often loosen some fasteners, which will only affect the gloss of a ink. During the printing process, it is also observed that it will affect the fluidity of ink on the ink bucket roller. In fact, magenta ink with high yield stress has poor fluidity in ink bucket

Figure 2 Flow curve of low gloss washable ink a 8. Measurement accuracy

Figure 3 Color fluidity curve of anhydrous a ink and ordinary ink

compared with the fluidity curve of the same color (magenta) a ink and ordinary ink in the ratio of 1:1 in Figure 3, it is found that the shear rate is low（