Solving Problems with Chemicals


d-Limonene : Biodegradable Solvent from Orange Oil

What is orange oil?  Orange oil is a by-product in citrus fruit juicing process. It is the major component which pressed out from rind that with higher commercial values. The orange oil which associates with the juice is subsequently separated and distilled to recover flavours, essential oil, and d-limonene. This d-limonene is categorized as food grade d-limonene. On the other hand, the d-limonene which extracted from the peel   by mean of steam extraction is called technical grade d-limonene. In other term, both are called orange terpene.

As for food grade d-limonene, it is generally recognized as safe ( GRAS ) by the Food Drug Agency ( FDA ), and many Kosher certified products are used as additives in consumer products which require sweet citrus fragrance.

As far as biodegradable solvent is concerned, technical grade d-limonene has been applied and included in countless of formulation of household and industrial cleaning products, leveraging its advantages of satisfactory solvency and detergency, natural occurring sweet orange aroma, and environmental  friendly. The specific gravity ( SG ) of pure d-limonene is approximately 0.84, therefore it is lighter than water. The colour of the fluid may vary from water clear to light yellowish depending on purity and grades. Being an organic solvent with flash point as low as 49 degree Celsius, it is categorized as combustible liquid.

One interesting aspect of this Environmentally  Preferable Product ( EPP ) --  the Kauri-Buthanol Value is greater than mineral spirits, and similar to that of CFC’s ( see chart below )

“  Kauri-butanol value "Kb value" is an international, standardized measure of solvent power for a hydrocarbon solvent, and is governed by an ASTM standardized test, ASTM D1133. The result of this test is a scaleless index, usually referred to as the "Kb value". A higher Kb value means the solvent is more aggressive or active in the ability to dissolve certain materials. Mild solvents ( hexane ) have low scores in the tens and twenties; powerful solvents like chlorinated solvents ( TCE )  and naphthenic aromatic solvents ( xylene, toluene )  have ratings in that are in the low hundreds. “

Hence, d-limonene has better solvency properties compared to petroleum-based terpene and mineral spirits; this allows greater flexibility and performance in formulating cleaners for removing some stubborn stains.  d-Limonene has been successfully replaced many petroleum-based solvents, including mineral spirits, toluene, xylene, ketones, glycol ethers, and particularly certain chlorinated and fluorinated solvents associate with adverse environment impact and ozone depleting tendency.

 However, in cases where d-limonene is not powerful enough to remove certain tough, resinous materials, a more acceptable, low toxicity   glycol ether  like propylene  glycol  ethers  can be added to increase the solvency of end products.

The ease of d-limonene being emulsified in a water dilutable formulation is also a winning point for its use in water-based cleaning products. By combining  d-limonene with surfactant(s), water diluting version of carpet stain removers, engine degreasers, floor cleaners, kitchen and oven  cleaners, water rinsable part cleaners  to name but a few, can be formulated and fire hazard of d-limonene is very much reduced.

Although the use of d-limonene has been regarded as safe to human being, one must not ignore its effect of removing one’s skin oil and causes dryness and cracking, and dermatitis in long term direct contact. Besides, long term exposure to this volatile organic compound ( VOC ) must also be cautioned though the evaporation rate may be lower compared to other toxic chemical solvents. Being a combustible substance with low flash point, it must be treated as hazardous waste for disposal, conforming to Local, State, and Federal Regulation