Green Solvents: Agrochemicals in Place of Petrochemicals
The challenge to replace petrochemical solvents in all facets of industry has never been greater. The growing need to create a cleaner environment coupled with the stringent regulations being enforced to make that possible have affected companies large and small. Alternatives to traditional solvents have been somewhat successful, but not without a high price tag for capitalization or a change in product performance.
Another option to petrochemicals--a revolutionary development -- offers many opportunities to businesses without significant financial obligations but with the chance to improve results. Referred to as "green solvents," "environmentally friendly solvents" or "biosolvents," this family of products is known for its unique composition. Green solvents are based on high purity agrochemicals, which are derived from the processing of agricultural crops. Ethyl lactate, for example, is derived from processing corn.
VertecBio(tm), or ethyl lactate (ethyl alpha-hydroxy propionate), is the ester of lactic acid, a natural organic acid. Lactic acid is commonly used in cultured dairy products, salts, adhesives, general-purpose food additives, cosmetic products and in the manufacture of lactates. Lactate ester solvents are now being used in many industrial applications including specialty coatings, inks and cleaners.
Ethyl lactate has many attractive characteristics that translate into environmental benefits and performance advantages. It is 100%-biodegradable and breaks down into carbon dioxide and water. It is easy and inexpensive to recycle. It is non-corrosive, non-carcinogenic and non-ozone depleting. It has no HAPS and is not SARA 313 (Superfund Amendment Reauthorization Act) reportable so there are no oral or inhalation toxicity problems. It has no environmentally hazardous ingredients and no global warming compounds. And because it evaporates slowly, it is considered a very low volatility VOC.
As a solvent in formulated products like coatings, ethyl lactate enhances the performance of various resins, polymers and dyes because of its high solvency power, high boiling point, low vapor pressure and low surface tension. Good wetting properties for a variety of pigments and good penetration in natural materials are among other performance characteristics.
In high-solids paints, its high solubility (see Table 1) makes it a desirable solubility booster; in dispersed pigments and concentrated inks, it provides solubility, pigment wetting and formulation stability; and in phenolic resins, polyvinyl phenols, diazo resins and nitrocellulose resins, it is used for resin solubility, surface wetting and control of evaporation rate.
In formulating coatings for polystyrene surfaces, its ability to etch certain types of plastic substrates improves adhesion. For wood, polystyrene and metal coatings, it improves penetration, adhesion, pigment wetting and provides resin solubility; and in leather and wood coatings, with low surface tension and a chemical affinity for natural materials, it helps achieve good penetration.
The applications for ethyl lactate go beyond its use in coatings. It has proven to be a very effective paint stripper and graffiti remover. Because it replaces solvents such as NMP, toluene, acetone, and xylene, that have long been accepted as the standard (see Table 2), ethyl lactate helps make the workplace safer. It does not require extensive venting or concerns about EPA requirements. The combination of low VOCs and a non-carcinogenic material means no exposure limits.
In pre-production surface preparation, ethyl lactate is an excellent cleaner without the hazards and concerns associated with traditional products. For example, as a wipe solvent, it is particularly useful for metal finishing operations on large objects such as aircraft bodies or wings. For pre-bonding and pre-coating cleaning of metal surfaces, it can be used straight or in formulation with other solvents. It effectively removes greases, oils, adhesives and solid fuels. The evaporation is especially suitable for this type of application because it is slow enough to fully penetrate the contaminants without adversely impacting the overall operation. This penetrating ability makes it more effective than commonly used solvents like MEK and acetone that evaporate almost upon contact with the surface but without the safety hazards associated with these and other traditional solvents.
An excellent cleaner for the polyurethane industry, ethyl lactate dissolves a wide range of polyurethane resins because of its high solvency. In MDI line flushing, ethyl lactate is used to prevent polymerization. It immediately reacts with MDI end-groups blocking any reaction with water and crystallization, which makes it possible to restart equipment without extensive cleaning.
In the molding of elastomeric polyurethane foams, ethyl lactate (combining its high solvency and slow evaporating characteristic) reduces solvent use in each cleaning cycle and at the same time eliminates the use of chlorinated solvents.
Testing at Argonne National Laboratory demonstrated that VertecBio (ethyl lactate) outperformed conventional solvents for degreasing applications. Similar tests directed at paint stripping have also produced excellent results. Copies of the test results are available from VertecBio Solvents.
Recently, the Department of Defense initiated the "Development of Lactate Esters As Non-Toxic Chemical Depainting and Cleaning Materials" subtaskforce in an effort to eliminate or reduce the use of hazardous chemical and labor-intensive manual decoating and degreasing processes through the department. This subtaskforce is evaluating the effectiveness of lactate esters as paint strippers and cleaners on various weapon system components under the Pollution Prevention Initiative Task through the National Defense Center for Environmental Excellence Program.
Concurrent Technologies Corp., Edgefield, SC, began investigations into which lactate esters to evaluate. According to Project Manager Mary Nelson, VertecBio Solvents was selected as the supplier of solvents. Four variations of ethyl lactate and methyl soyate blend were supplied. The lactate esters will be tested on panels and coupons representing the weapon system components. The demonstration activities will include performance and mechanical testing to ensure that the esters are viable alternatives to current paint strippers and cleaners while causing no detrimental effects to the substrate material.
A total of 32 mechanical evaluations will be performed. Nine of these evaluations are physical and chemical property determinations, such as non-volatile residue (NVR), biodegradability and storage stability. The remaining 21 evaluations are for material compatibility. Eight of these are corrosion tests including total immersion, dissimilar metal, stress and stock loss. Other material compatibility evaluations include hydrogen embrittlement, effects on painted and unpainted surfaces, adhesion, adhesive bonding, and fluorescent penetrant inspection. Test results are expected to be completed in six months.
The transformation from harmful petrochemical based solvents to products that can be used safely -- without affecting the environment, the performance of the product and the need for significant capitalization -- has been challenging. No company is immune from the effects of traditional solvents and the strict regulations to limit their use. Agrochemicals such as VertecBio Solvents's ethyl lactate solvents are proving to be a most practical alternative particularly for paint and coatings applications. c
For more information on green solvents, contact Mark Henneberry, 1441 Branding Lane, Suite 100, Downers Grove, IL 60515; phone 309/527.4224; fax 309/527.2230; e-mail firstname.lastname@example.org; visit www.vertecbiosolvents.com; or Circle Number 144.