Bio Based Alternative Solvents
How Well Do They Work
by Jason Marshall with Heidi Wilcox
Cleaning Issues & Product Selection
Identifying a substitute for solvents in cleaning applications is not an easy task. There are literally thousands of formulations to choose from. The variability of the literature for these products changes from vendor to vendor and as well as from product to product, making the search for an applicable substitute nearly impossible. Even after selecting a potential product, there is no guarantee that it will work.
Bio Based Alternative Solvents
SSL has investigated several solvents based on renewable feed stocks: Bio Polyesters (PHAs), Methyl Soyates, Ethyl Lactates and Citrus terpenes/oils. The laboratory focused its testing on product performance on a variety of soils, substrates.
Product Testing at SSL
Since 1993 the Surface Solutions Laboratory has conducted 1500 trials for over 250 companies evaluating nearly 500 cleaning formulations. Specifically, testing at SSL has led to more than 100 trials that have investigated the effectiveness of approximately thirty bio-based products from multiple vendors. These products have been evaluated for removing 21 different classes of contaminants with 97 specific contaminants. Following the client specific testing, the lab established a testing matrix of the bio-based products to evaluate these cleaning products in a direct comparison of twenty two specific contaminants in twelve contaminant fields. The bio-based products were grouped according to the following classes:
|Soy Methyl Ester||SME||Soy oil is heated and reacted with methanol in the presence of a catalyst|
|SME & Lactate Esters||SL||Mix of SME and LE|
|Lactate Ester||LE||Process uses sugars, starches and oils through high performance microbial fermentation|
|Lactate Ester & D-Limonene||LD||Mix of LE and D-L|
|D-Limonene||D-L||Oils extracted from citrus rinds|
The contaminants were divided into two classifications: Metal working fluids and non-metal working soils. The metal working fluids consisted of two cutting fluids, one coating, two greases, one lubricant and one quench oil. The non-metal working soils contained two adhesives, two buffing compounds, one coating, two fluxes, two inks, two paints, two resins and two waxes.
Metal Working Fluids
During the metal working fluids cleaning comparison, nineteen products were evaluated. Six products were soy methyl esters, three were soy methyl ester & lactate mixtures, one was a lactate ester, one was a lactate ester & d-limonene mixture, and eight were d-limonene based.
Eleven of thirteen products removed over 85% of the cutting fluids. The remaining two SME products removed less than 80% of the cutting fluids. Four products, three D-L and SL, removed over 85% of the rust preventative coating (Coating 2). Four products, all D-L, removed over 92% of Grease 1. For Grease 2, only two products, 1 SL and 1 D-L, were successful. All fifteen products were successful in cleaning the lubricant. All but two products, both SME, removed over 84% of the quench oil.
Nonmetal Working Soils
During the non-metal working soils cleaning comparison, twenty products were evaluated. Six products were soy methyl esters, four were soy methyl ester & lactate mixtures, one was a lactate ester, one was a lactate ester & d-limonene mixture, and eight were d-limonene based.
One D-L product was successful in removing Adhesive 1 while there were eight other products that had little effect on the adhesive. None of the products tested could remove Adhesive 2. Four D-L products removed over 90% of the two buffing compounds. In addition, four SME removed over 80% of Buffing compound 1. However, none of the SME removed 75% of the second buffing compound. The coating was not easily cleaned by the products using immersion cleaning. Three D-L removed around 50% of the coating. It was noted that many of the products allowed for the coating to be easily peeled off the stainless steel surface. With the peel the three D-L had over 90% removal. In addition, one SME and two SL's removed over 98% of the coating. The six products tested for flux cleaning were successful in all but one product on one of the fluxes. The SL removed just over 50% of Flux 1 but removed 85% of Flux 2. Ink cleaning resulted in limited success for all the products tested. Two D-L cleaned over 65% of Ink 1 and 2, while one SL removed over 90% of Ink 2. Three products, one LD, SME and D-L, removed 92% of Paint 1. The same D-L removed over 92% of Paint 2. None of the products had any effect on both resins, removing under 53%. Three D-L were very effective on Wax 1, resulting in over 99% removal. In addition, two of these D-L were successful on Wax 2, removing just over 83%.
Summary of Bio-Based Testing
The bio-based alternatives performed fairly well on many of the metal working fluids. These products resulted in cleaning efficiencies comparable to aqueous based formulations, petroleum distillates and trichloroethylene for the cutting fluids, the lubricant and the quench oil. The d-limonene based products tended to be better suited for the heavier metal working fluids like the greases and the rust preventative coating. For many of the soy based products, film residue decreased the initial efficiencies. By altering the rinsing (spray) and or drying (high velocity air blow off or wiping) methodologies, this residue could be reduced or eliminated. For the non-metal working soils, the d-limonene products had a wider range of success than the soy and lactate products.
The bio-based solvents evaluated at SSL were shown to have many possible uses in surface cleaning applications. Attention to cleaning methodology, including rinsing and drying, will allow for optimum effectiveness to be achieved for the soy and lactate products.