Biochemical Substitutions in the Paint Industry

The manufacture of paint and coatings produced over 92 million pounds of toxic chemical releases and transfers in the Great Lakes basin during 1992. Analysis of EPA's Toxic Chemical Release Inventory (TRI) data shows that in the paint industry, most pollution from the manufacture of paint consists of chemicals such as xylene, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and acetone, which are used as solvents [1]. In paint formulations, solvents provide the necessary viscosity that allows paint to be applied as a liquid. Solvents from paint can be released to the environment from spills, as a component of paint which is discarded, and through evaporation during the manufacturing process. Solvents are also used for the cleaning of manufacturing equipment, which is estimated to generate more than 40 percent of waste from the manufacture of paint [2]. After paint is applied, these solvents evaporate from the paint film, and can pose a health hazard as well as contributing to low level ozone production and the formation of smog.

Biochemicals For Manufacturing Equipment Cleaning

The cleaning of paint manufacturing equipment is frequently carried out with toxic solvents such as MEK, MIBK, xylene and toluene [3]. The substitution of biochemicals for these solvents produces a less toxic waste stream.

Inland Technologies (Tacoma, WA) specializes in formulating alternative cleaning solvents tailored to meet the cleaning needs of their clients. Many of their solvents are based on the terpene d-limonene, a powerful natural solvent derived from the peels of citrus fruits. One such solvent, EP 921 (patent pending), is formulated to replace MEK, MIBK and lacquer thinners for cleaning applications. EP 921 has low volatility, which reduces fugitive emissions from cleaning processes. It contains no chemicals that are listed on the EPA 313 Toxic Release Inventory or as Hazardous Air Pollutants (HAPs). In addition, EP 921 has extremely high solvency, dramatically reducing the solvent waste stream for cleaning applications. One manufacturer replaced MEK with EP 921 and reduced the volume of their solvent waste stream by 95%. This company estimated that it would generate $9600 in savings annually from reductions in waste generation and solvent consumption [4].

Purac America (Lincolnshire, IL) manufactures the Purasolv® line of solvents. These solvents are esters of lactic acid, which is produced by the fermentation of sugar. A variety of coatings resins, such as acrylics, epoxies, polyesters, alkyds, nitrocellulose, and polyvinyl acetate are soluble in Purasolv solvents. Purac states that its lactate ester solvents are low in toxicity and biodegradable, and are not listed on the EPA section 313 Toxic Release Inventory or as HAPs. Lactate ester solvents have low vapor pressure and high solvency, and so reduce VOCs in both cleaning and formulation applications. Furthermore, these solvents are easily recycled through distillation [5].

Biochemicals for the Formulation of High Solids Coatings

Solvent use can be reduced directly by the formulation of high solids coatings, which have reduced solvent content. Biochemicals called diluents, which reduce the viscosity of coatings formulations, can be used to formulate high solids coatings without a loss in performance.

Cargill (Minneapolis, MN) manufactures the reactive diluent DilulinTM, which is derived from linseed oil. This diluent reduces the viscosity of alkyd and urethane coatings formulations, allowing decreased solvent use. The diluent cures into the coating, and consequently does not contribute to VOCs. It is not a HAP, and is not listed on the EPA section 313 Toxic Release inventory. Coatings formulated with DilulinTM have performance comparable to conventional high solvent content formulations, with better drying times and hardness and without the yellowing associated with coatings reformulated with linseed oil alone. DilulinTM is compatible with oil modified urethanes, long, medium and short oil alkyds, and other copolymer alkyds [6]. At $0.95-$1.05/lb, its cost compares favorably to conventional alkyd and urethane resins which cost $1.00-2.00/lb.

Industrial Oil Products (Woodbury, NY) produce Tungsolve 2000TM, a methyl ester derivative of tung oil. Tungsolve 2000TM acts as a solvent replacement in coatings containing oil modified resins such as alkyds and urethanes. This reactive diluent reacts completely into the finished formulation, significantly reducing VOCs in coatings formulations. Tungsolve 2000TM contains no chemicals listed on the EPA Toxic Release Inventory or as a HAP. At $1.15-1.31/lb, it is comparable in cost to conventional alkyd and urethane resin costs at $1.00-2.00/lb. In partnership with the American Tung Oil Corporation, Industrial Oil Products is working to revive the production of tung oil in America to insure a reliable domestic supply of this versatile natural oil [7].

Water Based Coatings

There is a significant trend in the paints and coatings industry towards water based coatings. Water is the most inexpensive and environmentally safe solvent available for the formulations of coatings, but traditionally it has been ineffective for many varieties of coatings resins, and water based paints have tended towards poor adhesion and durability [8]. Advances in technology are overcoming these limitations.

McWhorter Technologies (Minneapolis, MN) produces alkyd resins for water based coatings. Alkyd resins, which are frequently derived from vegetable oils such as soy, linseed, and sunflower, are among the safest available chemicals, but traditionally tend towards high solvent content in coatings formulations [9]. McWhorter manufactures water based alkyd resin dispersions that reduce solvent use by 50-80 percent and reduce VOC emissions by a comparable amount while achieving performance equal to conventional solvent based alkyd formulations [10]. These resins are not listed on the EPA Toxic Release Inventory or as HAPs. Priced at about $2.60/lb, these resins cost about $1.30/lb more than conventional resins. However, these biobased resins greatly reduce solvent requirements by replacing petrochemical solvents with water. Conventional solvent based formulations require 2-3 pounds of petrochemical solvents per pound of resin. The replacement of 2-3 pounds of solvents at $0.30-0.60/lb represents a savings of $0.60-1.80. Hence the use of these alternative resin dispersions can save up to $0.50 per pound of resin used.

Powder Coatings

Powder coatings are applied in powder form, completely eliminating the use of solvents. Powder coatings have high potential for eliminating solvent use and VOCs, although the high temperatures required to cure these coatings, around 250-450 degrees Celsius, limit their use primarily to coatings for metals [11].

Elf Atochem manufactures Rilsan®, a nylon 11 resin used in metal coating applications. Nylon 11 is not listed on the EPA Toxic Release Inventory or as a HAP. Rilsan® produces coatings with exceptional chemical and mechanical resistance. While nylon 11 resins are relatively expensive at $4.94-$7.94/lb, their markets are growing because of their low melting point of 186 degrees Celsius (compared to greater than 200 degrees Celsius for many resins) and superior abrasion, impact, and chemical resistance. The fact that nylon 11 resins do not require the additional curing step required by most powder coating resins further improves the economics of production by reducing processing time [12].

1. U.S. EPA , 1992 Toxic Chemical Release Inventory : SIC 2851.
2. U.S. EPA, Guides to Pollution Prevention: The Paint Manufacturing Industry, EPA/625/7-90/005, Washington, DC, June 1990.
3. Ibid.
4. Product information supplied by Eric Lethe, Inland Technology Inc, Tacoma, WA.
5. Product information supplied by John Ketelaar, Purac America, Lincolnshire, IL.
6. Product information supplied by Bill Reutz, Cargill Industrial Oils Division, Minneapolis, MN.
7. Product information supplied by Blake Hanson, Industrial Oil Products, Woodbury, NY.
8. Triplett, Tim, "Waterbornes make a splash," Industrial Paint & Powder, v. 71, January, 1995.
9. Triplett, Tim, "Resin manufacturers struggling for answers,"Industrial Paint & Powder, v. 70, November, 1994.
10. Product information supplied by Rich Johnson, McWhorter Technologies, Minneapolis, MN.
11. Ouellette, Jennifer, "Powder Coatings," Chemical Marketing Reporter, v. 246, October 10, 1994.
12. Product information supplied by Craig Schmehl, Elf Atochem North America Inc, Philadelphia, PA.

POLLUTION SOLUTIONS is a series of fact sheets about pollution prevention strategies with biochemical substitutes prepared by the Institute for Local Self-Reliance (ILSR). If you would like more information, contact:

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