Performance Comparisons of Heatset Ink Formulations

Environmental Resin ER-125 is a hydrocarbon-based resin created by ATDM Gilsonite Company for use in all types of black offset inks. The resin is soluble in aliphatic mineral distillates, comparable with hydrocarbon, phenolic and alkyd resins, and creates varnishes with low and stable viscosities. ER-125 is almost totally pure aliphatic hydrocarbon with less than 0.05 percent impurity content.

AGC's research shows that Environmental Resin ER-125 can provide the heatset ink maker with several major advantages. Several benefits can be achieved by using ER-125 Resin as either a full or partial replacement of the hydrocarbon (C5-C9's), phenolic and alkyd resins commonly found in black heatset ink recipes. ER-125 Resin's major benefits in a black heatset ink can be summarized as follows:

  • greatly increased flow;
  • low tack and excellent tack stability;
  • low tack and high gloss level at the same time;
  • high gloss level at lower solids level;
  • no misting;
  • excellent carbon black wetting; and
  • reduces raw material costs about 10 percent to 15 percent.

Tables 1 and 2 outline the logic employed in the research experiments. Seven different heatset ink formulations were compared. Each comparison changed one ingredient from the previous recipe to study the performance effect of that single change. For example, Column 1 uses Gilsonite Selects 300 Grade in the grinding media compared to Column 2 using ER-125 Resin. The objective of this change is to demonstrate that ER Resin wets carbon black as well as Gilsonite. Then, use Column 2 as a base. Columns 3 through 7 show how effective ER-125 Resin is as a replacement for the hydrocarbon, phenolic and alkyd resins in Column 2's formulation.

The objective of each comparison is summarized above in Table 2:

In our research, the resin modified phenolic resin used is Worleefen F-120. This is a fast setting, high gloss resin from Greece with a 120° C melting point and a viscosity of 1 Pascal second (30 percent solids in linseed oil). The unmodified hydrocarbon resin from Taiwan is SK-150 with a 150° C softening point. The alkyd resin used is Worleekyd L-3, a linseed oil-based product with 9 Pa.s. Viscosity, a 79 percent oil content and an acid value of 15.

The aliphatic solvent used is from Haltermann Oil Company in Germany. The PKWF 4/7 solvent has a boiling point range from 240° C to 270° C, a 20 percent aromatic content and a 72° C aniline point. Since the ink maker will produce a heatset ink by first making a free-flow varnish, then a grinding media, and finally a gel varnish, Tables 3 through 5 outline the individual formulations for each of these components. The objective of the free-flow varnish manufacture was to produce four varnishes with approximately the same viscosity, using one resin each - Gilsonite, ER-125, phenolic and hydrocarbon. These varnishes were essentially 50 percent resin plus 50 percent aliphatic solvent, except for FF#3, which required extra solvent to yield the desired viscosity . Please note that the initial viscosity of the Gilsonite varnish was very high and not equivalent to the other three.

Afterwards, two different grinding media were produced using the Gilsonite-based and the ER Resin-based free-flow varnishes. Both of these grinding media used Cabot's Regal 250-R carbon black having a jetness index of 90, a tinting strength of 98 and a surface area of 65 square meters per gram. The 250-R grade of carbon black has a high tinting strength, high gloss, low viscosity and a blue tone. The extra aliphatic solvent was used to equalize viscosity.

The gel varnishes were made using the ER Resin-based and phenolic resin-based free-flow varnishes. Each one used 2 percent stearic acid and 2 percent Manalox 205 gelling agent. Manalox 205 is an aluminum chelate product sold in Europe. The United States equivalent product would be OAO-HT (Oxy Aluminum Octoate - High Temperature) sold by Chattem Chemicals of Chattanooga, Tennessee.

Table 6 presents the actual heatset ink recipes using the free-flow, grinding media and gel varnishes shown in Tables 3 through 5. Again, the seven heatset inks were formulated to have approximately the same viscosities and extra aliphatic solvent PKWF 4/7 was used for viscosity equalization.

Table 7 presents a component analysis of the seven different heatset ink recipes shown in Table 6.

Table 8 presents the heatset ink performance results of the seven inks. There are many different relationships to consider in this presentation. It cannot be said that one ink is necessarily better than all of the others. What can be concluded is that substituting larger percentages of ER-125 Resin for alkyd, hydrocarbon and phenolic resins improves the quality of the finished heatset ink and also reduces raw material costs.

First, all seven inks were formulated to have approximately the same viscosity. Examining the yield values in Table 8, we see that all seven inks are demonstrating gellation, or "structure." Although the yield value of Ink #1 (2760) seems much higher than the other inks, all of these values are acceptable and essentially the same. Any yield value over 1000 is a demonstration of "structure," or gellation. The important point to note here is that Ink #7 develops its structure with ER-125 Resin in the formulation alone. The other inks are all using a combination of phenolic and/or alkyd resin.

The most important observations in Table 8 are the beneficial relationships between tack level, gloss level, flow and setting speed for the inks with increasing levels of ER Resin substitution. For example, moving from the standard Heatset Ink #1 (Gilsonite plus hydrocarbon, phenolic and alkyd resins) to either Heatset Inks #5, #6 or #7 (with large substitution levels of ER-125 Resin), the ink maker can achieve greatly increased flow (from 690 to 815),
reduced tack (from 74 to 60, initially) and slightly higher gloss (from 94 to 96) with acceptable setting speeds.

Even though the numerical value of Ink #7' s setting speed (2.65) seems much higher than the other inks, this increase occurs predominantly at the five second point. One must be reminded that in a practical printing situation the paper would have gone through a heated drier (at about 230° F or 110° C) directly after printing. This would minimize the longer setting speeds shown in Table 8, which are laboratory values without heated drying.

Comparing the setting speeds of Ink #1 (with Gilsonite for carbon black wetting) versus Ink #2 (with ER Resin), Ink #2's is slower. Also, comparing the setting speeds of Ink #4 (fully loaded with phenolic resin) versus Ink #7's (full ER-Resin substitution), #7's is also slower. Again, both of these effects are understandable because ER Resin is much more soluble in aliphatic solvents than either Gilsonite or phenolic resin. The basic rule here is that the better the solubility, the slower the setting speed.

Another benefit of ER-125 Resin (Ink #7) is that it gives the same gloss level as a phenolic resin-based ink (Inks #1 through #6) while also yielding lower
tack levels and increased flow, at the same time. This is an indication that ER-125 Resin-based inks will perform well on fast running printing presses, a fact
confirmed in the U.K.

Full ER Resin substitution offers the lowest initial and maximum tack levels with the highest level of tack stability. Also, Ink #7's flow is the greatest. Usually, ink makers prefer inks with lower tack levels because they permit faster printing speeds. However, lower tack levels normally imply low solubility of raw materials in the ink systems which give lower gloss levels, a big disadvantage. The heatset ink with large concentrations of ER Resin prove this theory wrong. They have both low tack levels, high gloss levels and high flow all at the same time, plus acceptable setting, good density and no misting.

ER-125 Resin offers the ink maker a wide variety of heatset formulations to choose from while always offering improvements in at least two or three major characteristics. ER-125 Resin enables the printer to achieve increases in flow and reductions in tack which, in turn, lead to fast printable ink systems for high speed heatset presses.

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