Writer Mark Twain once wrote: "The reports of my demise have been greatly exaggerated." The same can be said about solvent usage in the paint industry. Despite the continued migration towards waterborne technologies, and the growth of UV and powder, solvent-based products still have a place in the coatings industry. And the reason is quite clear: they work.
"Solvent-based technology still costs less and performs better than alternative technology," said Tom Newsom, product manager, global solvents, Eastman Chemical Company.
Because of that, end markets and customers still demand the performance that comes from solventborne formulations. One such market is automotive refinish. While waterborne products are being introduced, solvent technologies remain in use, and leaders in the market continue to launch new solventborne products. For example, Akzo Nobel Car Refinishes recently introduced Lesonal Basecoat SB, an advanced solventborne basecoat. Lesonal was launched in North America and throughout Europe this summer, and the product is being rolled out to the Asia-Pacific region this fall. The industrial coatings market requires products that can withstand the most extreme environments, and therefore, demands performance characteristics that come from solvent technology.
Yet even as paint chemists continue to move ahead by exploring low- odor and higher-solids products, the solvent industry remains in the environmental hot seat, facing regulatory pressure.
"New governmental regulations on HAPs taking place over the next year will affect all surface-coating operations in the U.S," said Richard W. Ryan, staff chemist, intermediates, ExxonMobil Chemical.
Currently, there are more than 188 products on the HAPs list, including some very common solvents used by the coatings industry such as MEK, xylene, MIBK, hexane and toluene, according to Mr. Ryan.
"These materials tend to be the solvents of choice for the coatings industry, with alternatives such as esters costing three to five times more," Mr. Ryan added.
A Move to MIR?
Industry suppliers and paint formulators alike are keeping a close eye on regulators as they ponder whether to continue with the current approach regarding VOC exemption of solvents, or move to Maximum Incremental Reactivity (MIR) methodology.
According to Mr. Ryan, a move to MIR would be a welcomed switch.
"We have a high interest in the MIR methodology. We believe that product regulations based on MIR have significant benefits versus the mass-based VOC approach. In mass-based VOC product regulations, all solvents are treated the same way, with the amount of solvent being used to determine an allowable concentration in the formulation."
Mr. Ryan continued, "In an MIR-based regulation, the solvent's potential to generate ozone is used, with the formulation subject to a regulatory limit. The MIR-type approach provides a science-based approach to truly reduce ozone in the environment while allowing the formulator greater flexibility to develop better products," Mr. Ryan said ExxonMobil Chemical is talking with various regulatory bodies and working with industry panels on the MIR approach.
Eastman also noted the importance of MIR and said it is working with the paint industry to reformulate aerosol coatings to meet MIR constraints in California.
Eastman Chemical Company is extending its product offerings by adding propionates, a class of ester solvents that helps formulators achieve the desired balance of solids and viscosity for their specific applications. "Propionates are an effective choice for helping formulators meet tough environmental demands such as HAPs and low-VOC requirements," commented Mr. Newsom.
Eastman is also offering what it calls a line of performance solvents, including n-butyl propionate, a HAPs-free, slow-evaporating urethane grade solvent with good solvency for most coating resins. According to Mr. Newsom, it provides an alternative for those seeking to enhance performance and reduce overall solvent usage. With low surface tension for better wetting, flow and leveling, n-butyl propionate offers high electrical resistance for ease of transfer in electro-statically applied coatings and improved atomization in sprayed coatings. Low water solubility helps minimize water pick up during storage, thereby increasing its shelf life.
"The trend near-term will be to replace 'regulated' solvents with solvents that perform better and are more environmentally friendly," added Mr. Newsom. "Eastman's specialty ketones (MAK, MPK, MIAK), propionates and EEP will afford coatings formulators a good range of options. In some cases the best bet will be to blend these with ester solvents to gain the desired results."
At ExxonMobil, in addition to work promoting the benefits of MIR, R&D staffers are addressing issues such as low odor and costs benefits of solvents.
When it comes to odor reduction, ExxonMobil's Isopar fluids are low odor and have low toxicity. "Several paint manufactures are using this type of technology effectively today," said Mr. Ryan. "In addition, they have very low reactivity or MIR values, making them a winning combination for the manufacturer, the consumer and the environment," he added.
As cost pressures continue along the entire supply chain, suppliers need to work closely with their customers. "Formulators need to be aware of all solvent offerings to optimize benefits versus costs, and they must have a quick and effective means of screening candidate formulations," said Mr. Ryan. "Solvents like MEK tend to be used extensively due to their high solvency and reasonable price. With the prospect of MEK being delisted as a HAP, it could play an increasing role, particularly in high-solids, low-VOC coatings."
Older Technology, New Tools
And while some would consider solvent-based coatings "old school," suppliers are using cutting-edge tools to assist customers in formulation endeavors.
"Formulators need to be aware of all solvent offerings to optimize benefits versus costs, and they must have a quick and effective means of screening candidate formulations," said Mr. Ryan.
To that end, ExxonMobil Chemical's computer modeling program provides customers with screening results when evaluating new formulations, and Eastman's solvents group is currently working on a new micro-site to help answer tough formulation questions, according to Mr. Newsom.