Volume 4, Number 3
Jul 1991

Soybean Oil-Based Inks Gain in Popularity

Several readers have inquired about soybean oil-based inks, presumably because they are concerned about their permanence or environmental friendliness. Unfortunately, there are no comparative studies known to the Editor on the permanence of contemporary printing inks. Ball point inks, yes; felt-tip inks, yes; printing inks, no.

Older manuscript inks are a different story. They have been studied because they are problematic. iron-gall inks ate right through the paper, even through parchment, and some fountain-pen inks based on aniline dyes would fade in the light and run if they got wet; but those inks were not used for printing.

If any readers have information m permanence problem with modern printing inks, especially when used with alkaline paper, the Editor and other readers would be interested in hearing about them.

The Use of Oils in Printing Inks

An article in the February High Volume Printing, "Making the Decision to Go Soy," by Pan Loman, gives some background facts that should be kept in mind when discussing the environmental significance of soybean oil:

There are four main kinds of ink, each suited to a separate kind of paper and press: heatset ink (for web offset), sheetfed ink, forms ink, and news (newspaper) ink. All of them contain a pigment, oil, solvent and resins or varnishes.

The extent to which soybean oil can replace the petroleum oil and/or solvent in conventional inks varies with the kind of ink. The greatest proportion of soybean oil (over half) is possible with news ink.

Although vegetable oils have been used in some inks for many years, the first recipe for soybean oil-based inks was not finalized until 1985, and it was not marketed until 1987. Soy inks now make up at least a third of the colored news ink market.

Soybean oil costs over twice as much as petroleum oil, so black soy-based inks cost 25% or so more, but they perform better on the press, with less spoilage at press startup, so printers are accepting them readily. Colored soy-based inks cost about the same as conventional inks because the expensive pigments, not the oils, determine the price. Colors are brighter and more stable throughout a run with soy inks (an especially big consideration with recycled paper).

Sheetfed and heatset soy inks have only been on the market for about a year.

Environmental Considerations

Petroleum-based inks contain relatively high levels of volatile organic compounds (VOCs), which are regulated by the updated Clean Air Act, as are the alcohol in fountain solutions and the solvents used to wash up presses between jobs. Soy inks will reduce VOC emissions in all three cases to a greater or lesser extent, because they contain less than half the VOCs, require less alcohol, work easier with alcohol substitutes, and can be washed up without solvents.

On the other hand, disposal of leftover soy ink is still a problem. All soy inks still contain some petroleum oils, and the pigments my contain heavy metals such as copper or barium. Therefore the inks may have to be disposed of as liquid hazardous waste, depending on local law. Whether the soy oil is biodegradable or not is therefore almost irrelevant.

The soy ink that gets printed on paper is harder to remove in deinking operations, according to an August 1990 article in Coating ("Effect of Different Printing Ink Formulations on Deinking"). The abstract says, "Binders containing linseed or soya oils or alkyd resins worsen deinking behavior."

Dick Drong, marketing r for sheetfed offset ink in Sun Chemical Corporation, wrote in to give some information on printing and environmental aspects. He emphasized as major advantages the reduction of VOCs and the fact that soy oil is a renewable resource grown domestically. When it is used in sheetfed offset inks, however, there is no particular advantage, because in these inks it only replaces another domestic renewable resource: linseed oil, which comes from the flax plant. So customers who are cultivating a "green" image on their publications cannot actually do anything for the environment by specifying soy-based inks for sheetfed offset work.