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Orange TKO

Orange TKO is D-Limonene, a naturally occurring substance.

First to understand that within the last 10 years much has changed in the use of solvents in the cleaning industry. Chlorofluorocarbons (CFC's), which were considered safe for more than 40 years, were found to be eating a hole in the o-zone layer, the earth's protective skin. For the same reasons, we have seen the demise of 1,1,1-trichloroethane, a popular spotting agent.

It had been customary to use petroleum-derived or halogenated hydrocarbon solvents or high levels of caustics and/or phosphates to clean soils such as greases, dirt, grime, asphalt deposits and burned or oxidized films. But all of those cleaning materials are either hazardous when used or provide residues that are increasingly troublesome environmental pollutants.

Solvents of the type mentioned above have several disadvantages. Some of the halogenated hydrocarbon solvents have been shown to adversely affect worker health, so their use either has been eliminated or drastically curtailed by regulations. Even when they can be used, the disposal of spent solvent in accordance with government regulations has become an onerous and expensive problem, especially for the smaller users who must avail themselves of the services of commercial disposal firms at considerable cost.

Also, many of these solvents and the compositions derived from them are flammable. This limits their use in situations in which fire and explosion are potential hazards.

Among the chemical alternatives turned to by manufacturers seeking to avoid these environmental problems is d-limonene. In addition to being a powerful solvent, d-limonene leaves a fresh fragrant, natural odor that dissipates over time. It can be used straight, thickened to a gel, or blended with a suitable emulsification system to produce a water-dilutable/rinsable product.

Origins in oranges

Limonene (without the chemical prefix "d") is a major component of orange and lemon oils and belongs to a group of hydrocarbon compounds known as monoterpenes. Monoterpenes, a subclass of terpenes, can have an acyclic or cyclic C10 hydrocarbon structure or can be their oxygenated derivatives.

Monoterpenes are natural products, are widely used in food and consumer products, have easy biodegradability, and have a long history of contact with people, so their toxicity is well established.

Ultimate source reduction

A particularly intriguing aspect of terpenes is that, because they are extracted from naturally occurring sources, e.g., citrus fruit peels, their use as cleaning solvents does not result in the release into the environment of any more materials than would occur naturally. Using naturally derived solvents as cleaning agents is the ultimate in source reduction.

Interesting properties

Pure d-limonene is a colorless, volatile (depending on the grade, it can have a yellow to off-white color) which is lighter than water. The commercial product has a boiling range of 310-352 degrees Fahrenheit. It has a flash point of 119 degrees Fahrenheit and is a combustible liquid. It has negligible solubility in water.

D-Limonene is a safer product than most solvents. Its oral LD 50 (lethal dose required to kill 50% of test animals within a specified time) is greater than 5,000 milligrams per kilogram (mg/kg) body weight. By comparison, the typical mineral spirit LD 50 is around 2,000 mg/kg body weight.

D-Limonene is also classified as a food additive and has been granted the FDA's GRAS status. It is no carcinogenic or mutagenic and is being evaluated for its chemopreventive and chemotherapeutic properties. Michael Gould, professor of human oncology at the University of Wisconsin-Madison Medical School, has found that d-limonene reduced the growth of breast cancer cells by 75% in test tubes as well as in rats.