Finding a new toolbox for metalworking fluids
By Alison Gaines
The metalworking fluids industry is often considered an “orphan industry” in the larger landscape of fuels and lubricants. At the 5th Annual Metal Removal Fluids Conference organised by the Independent Lubricant Manufacturers’ Association (ILMA) in September, speakers discussed some of the main challenges that the industry faces. Chief among them is chlorinated paraffins (CP), which are disappearing from additive options due to regulatory actions.
In use since the 1930s, chlorinated paraffins are, by most accounts, the most cost-effective extreme pressure additive on the market today. An extreme pressure additive works by forming a new tightly adhering compound between two surfaces. Chlorinated paraffins consist of a hydrocarbon backbone with elemental chlorine bonded to it at random places along the backbone. Hydrochloric acid is created as a byproduct.
Among chlorine’s various attributes is the fact that it works well at a wide range of temperatures, especially low temperatures, and it is effective at preventing the growth of microbes. For some applications, chlorinated paraffins are reportedly the only extreme- pressure additive that will do the job. CP have uses in many other industries besides metalworking, such as vinyl and polymer manufacturing.
CP are divided into four categories: short, medium, long and very long chain. Use of short-chain chlorinated paraffins, with fewer than 14 carbons, are no longer allowed by U.S. and European Union regulatory authorities because they are known to be persistent, bioaccumulative and toxic. Medium-chain (C14-C17) and long-chain (C18-C20) chlorinated paraffins are widely used as EP additives in the U.S. Within the last few years, very long-chain chlorinated paraffins (C21 and longer), previously grouped under the umbrella of long-chain, have become a category of their own.
The United States Environmental Protection Agency (EPA) is currently conducting its risk assessment for chlorinated paraffins. As Maria Doa, director of the Chemical Control Division at the EPA shared at the ILMA conference, the EPA was planning to finish its assessment by May 2016. However, Doa said that the EPA will probably push this back by roughly one year.
As part of the settlement of an enforcement action on the two companies in the U.S. who produce or import chlorinated paraffins, the companies agreed to cease the production and importation of short-chain chlorinated paraffins (SCCP). The companies also agreed that they would submit pre-manufacture notices (PMNs) for other chlorinated paraffins to the EPA for review. EPA has provided its preliminary determination to the companies of its review under the Toxic Substances Control Act (TSCA) Section 5(e). The companies subsequently informed some customers that they would have to cease all manufacture of chlorinated paraffins by May 31, 2016. Doa said that, based on concerns from users, the EPA would consider extending the date by about a year to 2017.
The EPA is also gathering critical use data on medium- and long-chain chlorinated paraffins. Critical use data, Doa said, is needed to answer the following questions about medium- and long-chain chlorinated paraffins: are they a less toxic substitute for something else? Do they have benefits in other uses? Are there substitutes, and do they work? The EPA is mainly trying to see if users of chlorinated paraffins can explain why CP are critical to their operation.
Doa said that the EPA has heard from many users that they need more time to provide this information or to transition to non-CP products.
At the ILMA conference, many speakers acknowledged that in the not-too-distant future, MCCP and LCCP will no longer be on the table because they will eventually be deemed persistent, bioaccumulative and toxic as well. The more optimistic speakers see this as an opportunity to develop new chemistries for the industry. Doa mentioned in her talk that very long-chain chlorinated paraffins seem not to have the same concerns associated with them and that there is testing being conducted to assess this. Doa understood that they are being considered for replacement of MCCP and LCCP in some formulations.
There are two manufacturers of CP in the U.S., but hundreds in China and Asia-Pacific, who are not so far restricted from producing short-chain chlorinated paraffins. These chlorinated paraffins cannot be imported into the United States. It should be noted that Asian manufacturers were not well represented at this conference.
The search for alternatives
So what does the post-CP landscape look like? Unfortunately, a formulator does not have the luxury of choosing components based on performance and compatibility alone. Jerry Byers, formerly manager of Research and Development in the Industrial Fluids division at Cimcool, expressed this sentiment in his talk, titled “How to Moveon from Chlorinated Paraffins.” This is the case because of regulations, he said. Formulating metalworking additives without CP would be like “trying to write a novel with fewer and fewer letters of the alphabet.”
Phosphorus and sulphur are also often used for extreme pressure lubrication as well as chlorine. However, as Byers explained, each has its drawbacks. Phosphorus, Byers said, has a tendency to cause algae growth in waterways, which takes oxygen away from marine life. It also feeds microbes in metalworking fluids, causing premature failure of the fluid. A sulphur-based extreme pressure additive, such as over-based calcium sulphonate, is not compatible with water-based fluids, which make up 80% of the metalworking fluids in the United States.
Much of the work of developing alternative chemistries falls to additive companies. Brett Wessler, a research manager at Lubrizol, spoke on his company’s attempts in this area. Lubrizol has conducted a tapping torque test, as well as a twist compression test, the latter of which is much more severe, on several extreme pressure additive options to determine which retained its coefficient of friction the longest. Over time, the additive gets “squeezed out,” as Wessler put it, and the lubricant fails. Sulphurised olefins, sulphurised fats, phosphorus compounds, over-based sulphonates and polymeric esters were tested at varying lengths of time, speed and pressure. Medium-, long- and very long-chain chlorinated paraffins were used as controls.
As Wessler explained it, the replacement of chlorinated paraffins can fall into one of three categories: the first in which a CP can be replaced with no operational changes, the second in which a CP can be replaced with some operational adjustments, and the third in which a chlorine-containing additive may be required. He explained that while not all the formulations performed as well as the CP controls, a formulator has to consider whether for a given application, a given replacement might be good enough.
All the speakers emphasised that there are many considerations for which additive, or combination of additives, might work for which application. Each application has its own set of considerations, such as activation temperature, pressure, duration, speed, type of metal and the end use of the metal part being created. Each application needs to be considered individually, and the search is not for an additive that behaves just like chlorinated paraffins—it is for a product that performs well enough for the given application.
Very long-chain chlorinated paraffins, or vLCCP, are being considered as one of the main replacement options for medium- and long-chain CP. In his talk, Byers offered them as a consideration, given that one day,vLCCP will be the only chlorinated paraffin available. With carbon chain length, he explained, viscosity tends to increase, so the viscosity of the final product might be too high for some end users. He also noted that it could take a higher concentration of vLCCP to get the job done, and that vLCCP are difficult to emulsify, and require completely different emulsifiers than its medium- and long-chain counterparts.
In any case, Byers said, and Wessler agreed, there is no one-for-one drop-in solution. Regardless of what the post-CP world looks like, costs will increase, and combinations of additives will be required.
Removing most chlorinated paraffins from the toolbox will create more problems besides just having to find different extreme pressure additives. A huge part of the metalworking fluids industry is biocides. Since most metalworking fluids are made with large amounts of water, and are often stored in tanks for long periods of time, bacteria and fungi flourish in these environments, and can damage the performance of the final product. Much like chlorinated paraffins, the biocide industry is under scrutiny from regulatory agencies, which creates additional constraints for metalworking fluid formulators.
Many of the alternatives to chlorinated paraffins, like phosphorus-based additives, are not as effective at controlling microbe populations. Therefore, as most of the speakers acknowledged, the future most likely holds more biocide involvement.
“There’s not a lot of products that are suitable for use in our industry,” said Michelle Rioux, technical service manager at Lonza Industrial Solutions. This has been a particular problem, she said, since the U.S. EPA began requiring dossiers on all chemicals that have antimicrobial uses. The dossiers included information such as product chemistry, expanded toxicology studies, exposure data, environmental fate information and applicator exposure, and have in some cases resulted in a product not being re-registered. When a product is allowed to re-register, it sometimes has usage restrictions or label amendments. Regardless, Rioux said, there is significant cost to the industry. In Europe, the Biocidal Products Regulation (BPR) is in the middle of a similar review as the U.S. EPA. In addition, it requires data sharing among companies to limit the use of animal testing. Many other countries including Asian ones require similar registration on a chemical inventory list, which often involves divulging sensitive data.
Formaldehyde-donating biocides, which are the most widely used type of biocide for their speed and efficiency, are one of the main targets of regulatory action. Adrian Krygsman of Troy Corp. gave a talk on formaldehyde and the current political and academic disputes on whether it is a carcinogen. In the European Union, formaldehyde is listed as a carcinogen. Because of this, many companies around the world are reluctant to invest in it anymore. Several U.S. institutions including the Food and Drug Administration and the National Academy of Science have concluded that it is a carcinogen as well. On top of this, many individual states have set occupational exposure limits, making it very difficult to produce a formaldehyde-donating product that will satisfy regulations in all places.
When concluding the meeting, John Burke, director of engineering at Houghton International, gave voice to the general frustration that undoubtedly pervaded the audience when confronted with the EPA’s upcoming deadline and need for critical use data. This data takes much longer to compile than the given amount of time, he said. “We’re just scratching the surface. We’re nowhere near a production model.”
This idea of metalworking fluids as an orphan industry seems to ring true, once so many of its components, like its most popular additive and biocide, are being taken away.