For Printers
The use of soy oil-based inks has gained in popularity recently to address the environmental issues and reduce our dependence on foreign petrochemical-based oil for inks. Printing inks, today, fall under several classes that include:
- Sheetfed ink (dried by oxidation or polymerization)
- Newspaper inks (absorption, oxidation)
- Heatset inks (dried by the action of heat)
The popularity of Soy oil-based inks actually began several years ago as a replacement for petrochemical oils. Soybeans are plentiful and are a popular crop among farmers making it widely available. The use of soy oil would reduce our dependence on foreign-based oil to produce petrobased inks however, soybean oil is actually more expensive than petrochemical oils. Vegetable oils include soy, cottonseed, vernonia, sunflower, tung, linseed, and canola.
There are drawbacks however, with the use of soy oils. Heatset inks, for example, use a resin material to harden the ink during drying. Small amounts, usually around 10%, of vegetable oils are added to heatset inks to impart flexibility to the dried ink. For years linseed oil and other vegetable oils were used to accomplish this task. To use soy or any other vegetable oil as a base in place of a resin cannot be done, as the resultant ink would not harden. Vegetable oils, including soy, do not evaporate. This makes it unsuitable for use as the volatile portion of a heatset ink. The volatile portion of the ink gives viscosity or body. Heats set ink manufacturers are substituting the soy oil today in place of linseed oil as the modifier for the heatset varnish. It is ironic that the ink producers are replacing one vegetable oil for another. The advantage is that the ink manufacturer and printer can now claim the ink is "soy based" and more environmentally safe!
Sheetfed inks have used linseed oil as the base oil in ink for many years. Linseed oil was used, as it imparts good flow characteristics to an ink and converts into a solid over a long period of time (drying). To accelerate this drying process, additives are added, such as cobalt or manganese octoate. Over time, to improve drying and other physical properties, petroleum oils became the standard in many non heatset inks replacing vegetable oils.
News inks are the easiest ink to incorporate soybean oil due to the method of drying (absorption) and the physical nature of the inks (low viscosity, etc.). Soy inks have gained popularity with newspaper printers due to the EPA considerations on petroleum based inks. The uses of soy oil as well as other vegetable oils reduce the total volatile or VOC (volatile organic content) content of an ink. The EPA has ruled that even the heavy oils used in news inks are considered volatile and can be considered air pollutants. The EPA has also ruled that soy and other vegetable oils are not as "volatile" and do not constitute any major threat to the air environment.
While there are disadvantages, there are many advantages in using Soybean oil. Soybean oil is much clearer than other vegetable and petro-based oils. This results in the printed colors being sharper and brighter. There are claims that the soy-based ink de-inks easier than its petroleum based counter-parts, however there are also claims to the contrary.
Soy oils are, however, more expensive than petroleum oils, and the price varies with the market. It has been difficult to produce good quality inks, made with soy oil, that has good rub resistance. This has proven to be one problem area for newspaper publishers.
While there have been many claims of the ecological benefits to be gained, ink made with soybean oil contain waxes, pigments, and other additives. This makes it no easier to dispose of a soy oil-based Ink than a petro-based ink, printed or non-printed. This requires that the same considerations be taken for disposal in a landfill or incineration as petro-based inks would need. While soy or vegetable containing inks may help reduce the measured VOC's (volatile organic compound content), the EPA (Environmental Protection Agency) has not exempted vegetable oils as a non-VOC. The EPA believes that while all vegetable oils are not VOC's, they are "precursors to precursors of ozone". When vegetable oils, including soy, dry by oxidation, there is evidence that minute amounts of VOC's are released, so says the Environmental Conservation Board. While the EPA and the ECB have made these statements, they do believe they (soy inks) are much more friendly to the air environment than petro-based oils. The same would hold true for any other vegetable oil based ink.
The American Soybean Association (ASA) was very effective in the late 1980's at promoting the use of soy oils in printing inks and established minimum percentages of soy oil content in order for the SoySeal to be displayed on an ink can or a printed piece. As of 1994, the thresholds were 30% for colored new inks, 40% for black news inks, 20% for business forms inks, 20% for sheet-fed inks and 7% for heat set inks.
Press-related problems with soy oil inks have been related mostly to drying. Soy inks dry (due to the soy oil) at a slower rate. Most problems have been encountered in the newspaper area. This is, however, being rapidly overcome. Soy inks will find a definite use in several areas in the printing industry where it can replace petroleum hydrocarbons and reduce our demands on a non-renewable resource. However, it is not a panacea for the environmental problems that the printer and consumers of print face.
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