About Chemical Innovation - Subscription Information
May 2001
Vol. 31, No. 5, pp 22—27.
Developing Technology

Table of Contents

Stephen G. Wildes

Clean machines from beans

What do industrial cleaners, paint solvents, diesel fuel, and nail polish remover have in common? They can all be produced using soybean-derived esters.

opening art
Photo courtesy of the United Soybean Board
The lowly soybean has long been an excellent food for humans and animals. But two of its major components—oil and protein—offer significant utility as industrial chemical feedstocks. The United Soybean Board recognized the potential for industrial product development and launched a program in the mid-1990s.

Congress established the United Soybean Board (USB) in 1991 to create greater demand for and increase the value of soybeans. It is a producer-run organization that funds growth development by investing checkoff program revenues generated by the sale of soybeans. In the checkoff program, 0.05% of soybean revenue in the United States is shared equally by the USB and the soybean boards of the producing states.

The effort to develop and commercialize new soy-based products is a very broad program involving industry, universities, private research organizations, and government agencies. As a result, dozens of industrial companies are producing and marketing numerous new products that compete effectively with existing petroleum-based chemical products.

The focus of industrial product development has been on five primary market segments:

  • coatings and printing inks;
  • adhesives;
  • lubricants;
  • plastics and composites; and
  • specialty chemicals: solvents, surfactants, and pesticides.

New commercial products that have been introduced include finger-joint wood glues, urethane polyols, interior trim paints, plastic composites, printing inks, metalworking fluids, specialty lubricants, and industrial solvents. The majority of these products are made from soybean oil, one of the most plentiful and least expensive sources of fatty acids. It is renewable and provides many environmental benefits as a chemical feedstock, including biodegradability and low toxicity.

Methyl soyate—properties and applications
Many new commercial soy-based products have been generated for the solvents market. Soy solvent development has focused on soy methyl esters, commonly referred to as “methyl soyate”. The manufacturing process for methyl soyate is the simple transesterification of soybean oil and methanol with a sodium hydroxide catalyst, affording glycerin as a coproduct (Figure 1 below).

Figure 1. Methyl soyate is produced by transesterification of soy oil esters.
Figure 1. Methyl soyate is produced by transesterification of soy oil esters.
Although the current major industrial use of methyl soyate is for solvents, initial production of soy methyl esters began in the mid-1980s for biodiesel fuel development. There are now 10 commercial plants in the United States with ample capacity available for industrial uses because biodiesel demand has been slow to develop.

From a performance standpoint, methyl soyate provides effective solvency, is low in volatile organic compounds (VOCs), has a high flashpoint, is nontoxic, and is compatible with other organic solvents and most metals, plastics, and elastomers. Its principal properties are shown in Table 1. Despite its good solvent properties, methyl soyate is typically not used neat because it evaporates slowly and leaves residual film on surfaces. In most applications, it is formulated with cosolvents or surfactants to meet specific performance requirements. Slow evaporation can be an advantage in many applications, such as ink removal and paint stripping, by extending the duration of solvent action and reducing solvent usage.

Figure 2. The kauri-butanol value of methyl soyate is in the middle of the range of common solvents.
Figure 2. The kauri-butanol value of methyl soyate is in the middle of the range of common solvents. Source: Reference 1.

Figure 3. The volatile organic compound (VOC) content of methyl soyate is far lower than solvents in current use.
Figure 3. The volatile organic compound (VOC) content of methyl soyate is far lower than solvents in current use. Source: Reference 5.

Figure 4. Methyl soyate?s flash point exceeds those of other common solvents by 250 °F or more.
Figure 4. Methyl soyate’s flash point exceeds those of other common solvents by 250 °F or more. Source: methyl soyate producer literature.
Of the benefits mentioned, the most important are solvency, low VOC content, and a high flash point. “Solvency” is often measured by the kauri-butanol (KB) cloud point test (4). The KB valuerepresents the maximum amount of a solvent that can be added to a stock solution of kauri resin (a fossil copal) in n-butanol without causing cloudiness. Because kauri resin is readily soluble in n-butanol but not in hydrocarbon solvents, the resin solution will tolerate only a certain amount of dilution. “Stronger” solvents such as toluene can be added in a greater amount (and thus have a higher KB value) than “weaker” solvents like hexane. Methyl soyate’s KB value compared with common solvents is shown in Figure 2 at right.

When its VOC content is compared with other solvents, methyl soyate is clearly preferable from an environmental standpoint (Figure 3 at right). Likewise, its flash point is considerably higher than those of competitive solvents (Figure 4 at right). These properties make methyl soyate a safe, environmentally friendly alternative for chlorinated, petroleum-based, and oxygenated solvents in many industrial applications.

Creative specialty chemical formulators have recently launched several new industrial and consumer products that use methyl soyate’s solvent properties and cosolvent compatibility. These products are designed for problem market applications requiring safe solvent replacement.

The primary market application for methyl soyate, which takes advantage of its solvent properties, is industrial cleaning and degreasing. Methyl soyate works well in products formulated with cosolvents or surfactants to accelerate drying and water rinsing. Methyl soyate can help to replace environmentally unfavorable petroleum and chlorinated solvents in basic parts cleaning. Formulations with other cosolvents such as ethyl lactate work well in the more stringent cleaning processes used in the electronics and aerospace industries. Other potential uses are in ultrasonic cleaning, household cleaners, food processing industries, and asphalt handling.

Resin removal and cleanup is a broad category with many cosolvent products currently in the field evaluation stage, especially in paint strippers, printing ink cleaners, and equipment cleaners. Field trials are under way on military aircraft and ships and at many major newspapers. Adhesive and anti- graffiti products containing methyl soyate are widely used.

Cosolvent blends
Blending methyl soyate with other organic solvents can synergistically enhance the properties of each individual solvent. A patented commercial example is Vertec Gold, a blend of methyl soyate and corn-derived ethyl lactate, produced and marketed by Vertec Biosolvents (Mount Prospect, IL).

Ethyl lactate, used neat, is a strong solvent, but it has a relatively high VOC content and a low flash point. The blend ameliorates both properties of ethyl lactate and improves the drying rate, residue deposition, and water rinsability of methyl soyate. Blending also lowers the cost compared with straight ethyl lactate. Both solvents are derived from crops, so they are renewable as well as biodegradable. Vertec Biosolvents patents on the composition and use of the blends were issued in 2000.

Vertec Gold was recently tested and evaluated by Argonne National Laboratory for parts cleaning and degreasing in their Central Shops. A summary from the pilot project report is given in the box, “Testing Vertec Gold” (6).

Cleaning up oil spills
CytoSol Shoreline cleaner is one of the exciting new technologies based on methyl soyate. This product was developed by CytoCulture International (Point Richmond, CA) to clean up oil spills on coastal beaches and in inland waters (7). It is listed on the Environmental Protection Agency’s NCP (National Contingency Plan) list (8) and is licensed by the state of California as the only allowable shoreline cleaner (9). It can also be used to bioremediate weathered oil spills at refineries or tank farms and clean reactors and storage tanks currently in use.

The selection process used by CytoCulture to develop the most effective solvent medium for oil spill remediation involved finding the right combination of performance properties, petroleum solvency, specific gravity, recoverability, and biodegradability. Methyl soyate was identified as having the best combination of these properties, and the CytoSol process was developed to enhance its performance.

The CytoSol process is a two-step cleanup technology for removing spilled oil accumulated on shorelines, breakwaters, piers, riverbanks, and other waterway structures. In the first step, the process uses a vegetable-oil–based biosolvent containing methyl soyate to release and recover the weathered petroleum. The CytoSol process expedites the removal of spilled oil through the specific physical and chemical changes it imparts to the petroleum, such as

  • dissolving the petroleum and decreasing its viscosity by dilution;
  • decreasing the adhesion of the oil to shoreline and structure surfaces;
  • increasing the cohesiveness of the oil, promoting its consolidation;
  • decreasing the specific gravity of the oil, allowing for separation and recovery by flotation on water; and
  • increasing the biodegradation rate of residual petroleum by exposing more surface area.

In laboratory simulations and field trials, the CytoSol process was found to release 50–90% of the original oil adhering to or trapped in various shoreline sediments ranging from riparian vegetation and fine estuary sands to coarse California beach sand and gravel in Prince William Sound. This first step required only a single CytoSol application followed by extensive washing with ambient-temperature seawater to flush out the floating oil–CytoSol mixture. In the second step, the remaining CytoSol biosolvent and residual petroleum hydrocarbons are degraded by bacteria present at the site. The bacterial action is supplemented by a program of nutrient enhancement and oxygenation. Following the formulation and application development of the CytoSol process, the biosolvent was subjected to thorough testing for marine toxicity, marsh plant survival, and biodegradation under the guidance of several state and federal environmental agencies to achieve EPA listing and California licensing.

Many more applications
Methyl soyate should be useful as a carrier solvent (a solvent that can solubilize resins or act as a diluent). Little development has been done in coatings, although commercial wood and concrete stains and corrosion protection additives containing methyl soyate are available. Methyl soyate has also been used for years as an agricultural adjuvant under the name “methylated seed oils”.

One of the early applications for methyl soyate was in fuels and lubricants. Numerous lubricant products are being marketed or are in development, including household lubricant sprays, metalworking fluids, form-release agents for asphalt, and concrete and lubricity additives.

The primary commercial fuel product is biodiesel. It has been in development since the late 1980s and was recognized last year by an act of Congress as the only alternative fuel to meet the performance requirements of the Clean Air Act of 1990. As a straight fuel, it reduces airborne toxins by 90%, compared with standard diesel fuel and it provides excellent lubricity for extending engine life, replacing sulfur compounds. Because of its high cost, it is typically used as a 20% blend (B-20) with petroleum-based diesel. Commercial use in bus and truck fleets in the United States is growing because of the recent surge in fuel prices. The similar use of grapeseed-based methyl esters as biodiesel fuels is even greater in Europe.

Many new methyl-soyate–based products have been introduced into the consumer products area. On the basis of its environmentally friendly properties (low toxicity, low VOCs, and biodegradability) and the growing interest in renewable ingredients, the use of soy methyl esters is increasing in products such as hand cleaners, skin lotions, nail polish removers, and auto polishes.

The environmental, product performance, and economic advantages of soy-based derivatives such as methyl soyate for industrial and consumer applications have created widespread interest and support from private industry and government agencies for the replacement of petrochemicals. As a result, technical and commercial development of these products continues to grow.

The soybean is a natural, annually renewable feedstock for industry. Work supported by the United Soybean Board’s New Uses Program by universities, government agencies, and industrial companies is creating significant results.

Acknowledgment
Methyl soyate product and commercial development work is supported by funding from the United Soybean Board, New Uses Committee.

References

  1. Farella, J. Physical and Cleaning Performance Properties of Methyl Soyate. Philip Services Corp.: Midland, MI, 1997.
  2. American Society for Testing and Materials. ASTM Annual Book of Standards; ASTM: West Conshohocken, PA.
  3. Laboratory study no. WIL-275003, WIL Research Laboratories, Ashland, OH, 1996 (on rapeseed oil).
  4. http://palimpsest.stanford.edu/byauth/burke/solpar/solpar3.html (accessed May 2001).
  5. Lazaro, M., DL Laboratories, New York, personal communication, 1999.
  6. Trychta, K. Evaluation of Environmentally Benign “Green” Solvent Blend Vertec Gold for Machine Shop Parts Cleaning and Degreasing. Argonne National Laboratory: Argonne, IL, 2000.
  7. Lopez, D. Letter to CytoCulture International Inc. U.S. Environmental Protection Agency: Washington, DC, Jan 30, 1997.
  8. U.S. Environmental Protection Agency. National Oil and Hazardous Substances Pollution Contingency Plan (NCP). Fed. Regist. 1998, 63, 51529–51530.
  9. Bontadelli, P. License for Oil Spill Cleanup Agent. State of California, Department of Fish and Game: Sacramento, June 1, 1997.

Stephen G. Wildes is a commercialization manager at Omni Tech International Ltd. (2715 Ashman St., Midland, MI 48640; 517-631-3377, ext. 235; swildes@omnitechintl.com). He received his B.S. in geology and his M.B.A. from the University of Michigan, Ann Arbor. He was with Dow Chemical Co., Midland, MI, for 25 years in business and marketing management for industrial chemicals, plastics, and membrane separation systems. He can be contacted for more information, supplier contacts, and a list of commercial products.


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"This is the hottest new collectible!
It's a Soy Beanie Baby!"

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