Chlorinated Paraffins (CPs) are chemical compounds found in plastics, rubber, paints, adhesives, and miscellaneous other substances. However, they are perhaps most effectively used as an additive in cutting oils and machining fluids where they function as a superb extreme pressure agent.
If the physical lubrication film breaks down due to heat, pressure, or both, the chlorine in the compound reacts with iron to form ferrous chloride which creates a chemical lubrication film. While there’s no debate over the effectiveness of chlorinated paraffins as a machining fluid, there is debate over its safety from both an environmental and health standpoint, perhaps affecting the future of these substances and the industries they serve.
How Are Chlorinated Paraffins Categorized?
CPs are formed by reacting hydrocarbon chains with chlorine. The CP can be categorized by carbon chain length and chlorine content percentage. In the United States, CPs are most commonly categorized based on the length of the carbon chain:
C10-13: Short chain chlorinated paraffin (SCCP)
C14-17: Medium (Mid) chain chlorinated paraffin (MCCP)
C18-20: Long chain chlorinated paraffin (LCCP)
C21+: Very long chain chlorinated paraffin (vLCCP)
History and Background
Chlorinated paraffins are produced by combining a hydrocarbon backbone and chlorine at a molecular level. While virtually any chlorinated compound will contribute extreme pressure properties, paraffins are chosen because they have proven to be most effective at providing film strength. Chlorinated paraffins are classified by their chain length; short, medium, long, and very long. Lumping all chain lengths of chlorinated paraffins together is not correct, as they behave differently when released in the environment.
Short chain chlorinated paraffins (SCCP) have been in use since the 1930s. SCCPs are the most concerning from a health and environmental standpoint as they are proven carcinogens and are bioaccumulative. However, these types of chlorinated paraffins are not used in manufacturing, they are used in solvents and other more aggressive materials.
In 1976, CPs fell under scrutiny when the newly-formed Environmental Protection Agency (EPA) took an interest in evaluating their danger, primarily under the Toxic Substance Control Act (TSCA). Short, medium, and long chain CPs were identified for testing and, when testing was completed in 1995, most of the regulatory focus on was on SCCPs. However, the EPA found some risks with MCCPs and LCCPs in aquatic studies, particularly with water-based metalworking fluids, but took no official action.
Further EPA Scrutiny
With some evidence of environmental issues already identified, CPs stayed on the EPA’s radar and, in 2009, the agency concluded that chlorinated paraffins overall were not adequately listed in its TSCA inventory. This meant any manufacturer hoping to sell CPs would have to resubmit information about their product and fill out a pre-manufacture notice (PMN). Any time a PMN is submitted to the EPA the agency essentially can treat it as a new product, opening the door for scrutiny and possible regulation.
In 2012 the EPA took its pursuit of CPs a step farther, placing all types of chlorinated paraffins on its list of TSCA Work Plan chemicals, and calling for a new chemical review process for all MCCP and LCCPs. In 2015, the EPA dropped the bomb on manufacturers, announcing MCCPs and LCCPs could not be produced after May 31, 2016. Any manufacturer wanting to produce them would have to resubmit a PMN – again opening the door for EPA regulation.
With no viable replacement for CPs as a manufacturing fluid, the industry banded together and put pressure on the EPA. The EPA responded by pushing the ban out to 2017 and, as of recently, completely suspended it.
Assessing the Risk
But is there a risk in using any chlorinated paraffin? The chemical manufacturing industry has submitted information proving that, when handled properly, MCCPs, LCCPs, and vLCCPs present no human health concern. It was also proven, when fluids are disposed of properly, there is no risk to the environment. The EPA has admitted it based CP assessments on worst-case scenarios, where products may not be disposed of properly or where exposure levels are abnormally high, instead of using information provided by manufacturers in their PMNs on how substances are disposed of and used.
CPs are valuable metalworking additives, so much so that without a workable replacement, any additive ban would likely have shifted manufacturing overseas, resulting in a huge impact on the manufacturing segment, as well as the economy.
A commitment to effective and safe options is needed, as well as continued use and testing on very long chain chlorinated paraffins (vLCCP) product options, and maintaining performance proven product lines based on MCCPs/LCCPs. The data gathered on vLCCP has shown them to be beneficial over the MCCP versions in labelling and regulation. The vLCCP versions will not require GHS marine pollutant labeling as is required for the other versions, meaning there will be fewer regulations when it comes to shipping the final product.
No one knows what lies ahead for CPs. But CP manufacturers will begin an immediate EPA-mandated study on the potential bioaccumulation of the medium and long-chain chlorinated paraffins. The data is set to be gathered over a five-year period and will also undergo a peer review process immediately following. Until that time, lubrication manufacturers can only turn to the best fluid options while continuing to develop better alternatives for future use. With continued best practices and ongoing assessment, there is no evidence that CPs will have any detrimental effect on humans or the environment.
This story originally appeared in the September/October 2017 issue of Precision Manufacturing, the Journal of the Minnesota Precision Manufacturing Association (MPMA).