Can Solventborne Coatings Make a Comeback

Let’s hope not. We may have to file this one under “Preaching to the Choir,” however the question in the headline bears a response. This query was recently posted on LinkedIn by an editor of one of the highly respected industrial paint magazines. It’s a good question, and I think a reply from a powder coating person is appropriate.

One of the things we powder people lose sight of is what alternatives exist for the industrial coater. We get our knickers all twisted when we consider the toxicity profile of one of our crosslinkers or when we explore which personal protective equipment (PPE) to use when applying our zero-VOC, HAPs-free coating technology. To keep things in perspective, let’s look on the other side of the industrial finish spectrum of technologies—the solventborne paint.

We can start with hazardous air pollutants (HAPs). The United States Environmental Protective Agency (U.S. EPA) defines them thus: “Hazardous air pollutants, also known as toxic air pollutants or air toxics, are those pollutants that cause or may cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental and ecological effects.” They currently count 187 compounds compound categories as HAPs, including many organic solvents. (ref: http:// www.epa.gov/ttn/atw/orig189.html) Many of these compounds are typically used in liquid paints and include:

• Toluene
• Xylene
• Ketones such as Methyl Isobutyl Ketone
• Glycol Ethers based on Ethylene Glycol
• Hexane
• Many Halogenated Solvents (e.g., PERC, TCE, ME)

Take a look at the Material Safety Data Sheet (MSDS) of a solventborne coating and you can gauge the toxicity of the solvent blend used to carry the paint solids to its target. We’re not talking about a little skin irritation or a case of dry mouth, folks. Here’s a quote from a toluene MSDS: “The substance may be toxic to blood, kidneys, the nervous system, liver, brain, central nervous system (CNS). Repeated or prolonged exposure to the substance can produce target organs damage.” (ref: www.sciencelab.com/msds.php?msdsId=9927301). These are dangerous chemicals.

And if you’re not too worried about worker exposure because you adhere to the highest standards of personal protective equipment let’s consider our environment. Most of the organic solvents used in solventborne paints are listed as volatile organic compounds (VOCs). VOCs are defined by the EPA as “any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions...” (ref: www.epa.gov/iaq/voc2.html#definition). This includes:

• Toluene & Xylene
• Most Esters (e.g. propyl and ethyl acetates)
• Most Ketones (e.g. MEK, MIBK, MPK)
• All Alcohols (e.g. propyl and isopropyl)
• All glycol ethers
• All hydrocarbon solvents

So, if you’re not poisoning your body by using solventborne paints, you’re contributing to air pollution by emitting solvents into the environment that photochemically combine with nitrous oxides to create smog. Smog is the major contributor to the huge global uptick in asthma, COPD and related respiratory diseases around the world. (see: https://www.epa.gov/ozone-pollution.)

If your finishing system is sophisticated enough to include costly oxidizers (or scrubbers) to convert solvent emissions to carbon dioxide and water (an expensive process to operate) so you don’t pollute, then you still have to examine the operating costs of using solventborne paints. The oversprayed liquid paint accumulates as a thick sludge that has to be disposed of. No one seems to have a good answer as to how to handle this hazardous waste product (see: www.finishing.com/0800-0999/816.shtml). And if there is no easy solution, then disposal costs can be enormous.

Another issue to face is the transportation, storage and handling of flammable, toxic materials. Department of Transportation requirements for transporting solventborne paints are onerous, which makes transport costs prohibitive. Once the material arrives at your receiving dock, it has to be handled by trained personnel and typically winds up in a storage area that looks more like a bomb shelter. These “paint kitchens” are adorned with National Electrical Manufacturers Association (NEMA) Class 1 electrical fixtures and switches, which cost five to 10 times as much as non-explosion proof counterparts. Not only does this add up to higher operating and capital equipment costs, but insurance premiums are invariably higher for solventborne finishing systems.

If you’re not convinced yet, think about quality. Solventborne coatings are difficult to apply as thick films (sags, runs, solvent-popping, etc.) and therefore seldom approach the abrasion resistance, durability or corrosion resistance of a thicker film powder coating. Even if you are ambivalent about toxicity, air pollution, hazardous wastes, flammability and durability, the bottom line is this: Solventborne paints offer less overall value compared to dry, non-toxic powder coatings. So, if you’re wondering if solventborne coatings will make a comeback…let’s hope not.