The Lubrizol Corporation
CONTRAM™ ST-1 Biocide – Globally Proven; Now Available in the United States

By Dr. Uwe Falk, Global Commercial Manager Biocides, The Lubrizol Corporation | TLT CMF Plus November 2012
 

Lubrizol’s CONTRAM™ ST-1 industrial biocide, an extremely effective antibacterial compound for use in aqueous metalworking fluids, was recently approved by the Environmental Protection Agency (EPA) for use in the United States.

Regulating biocides
Biocides are needed to control microbes; a fact well recognized within the metalworking industry. Without the use of biocides, bacterial counts in metalworking fluids rise rapidly, causing the fluid to spoil and resulting in an unhealthy work environment for machine shop employees. In the US, all biocide materials are regulated by the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) under the auspices of the EPA. FIFRA, which has been in effect for over 60 years, requires extensive data generation in consideration of a product’s health, safety and environmental impact as well as of its efficacy. This is an expensive process. Coupled with the high cost of new molecule development, the expense of registration in the US can be a limiting factor to new product introduction.

Approvals and Re-registration
The recent EPA approval of Lubrizol’s CONTRAM ST-1 product will remain in effect for the standard 15 year period. After that time, like all established chemistries, CONTRAM ST-1 will need to undergo Registration Review, which is replacing the Re-registration Eligibility Decision or RED program. Suppliers may want to consider approval, Registration Review and RED dates carefully when choosing a biocide. As re-registration dates draw close, biocide manufacturers will face the decision to generate additional data (if required by the EPA) or they may choose to drop out of the market due to the high cost of re-registration. Newly approved or re-registered products offer a significant window of stability. (To learn more about RED and Registration Review, watch for a Q&A with Lubrizol’s Phil Miller in the December issue of TLT.)


Figure 1. Spoiled metalworking fluid.

The formaldehyde question
Regulations are particularly pertinent to the discussion of biocides. The most effective biocide type for metalworking, one that has been used globally for years, is formaldehyde release chemistry. For many of those years, formaldehyde has been the regulatory focus of governmental and non-governmental agencies, with the current EPA threshold for exposure at 100 ppb over eight hours. A recent RED conducted on hexahydrotriazine, also known as HHT, brought issues surrounding formaldehyde to the forefront. HHT dominates metalworking fluid applications, and over the decades, it has been shown to be effective at a reasonable cost. However, with the recent RED, the EPA is giving serious consideration to regulating HHT to reduce the maximum treat level from 1500 ppm to 500 ppm in metalworking applications. The Canadian government is also discussing enacting similar regulations, although a final determination has not been made by either group. The regulators are seeing pushback from some in the industry, however, because HHT is ineffective as a biocide at those low treat rates.

CONTRAM ST-1: A reduced risk alternative
With an extensive history of successful application, the CONTRAM ST-1 biocide offers an alternative to HHT. The bound formaldehyde content of the CONTRAM ST-1 product is almost half of that of HHT, although the treat rate is also in the 1,000 to 1,500 ppm range. Unlike HHT, CONTRAM ST-1 is soluble in oil, a valuable characteristic for a product used predominantly in soluble oils and semi-synthetic oil emulsions.


Figure 2. N,N-methylenebismorpholine (MBM).

On November 2, 2011 CONTRAM ST-1 biocide, which has already successfully been used commercially in 36 countries over the past few decades, received FIFRA registration for use in closed (closed on all sides with mechanical exhaust) and enclosed (physical barriers controlling exposure to mist) machines. The registration covered not just the product, but a new active ingredient, which requires an even more rigorous approval process.

It’s important to note that the EPA approved CONTRAM ST-1 biocide despite heightened concerns about formaldehyde. In its risk assessment, the EPA noted that “the available formaldehyde is estimated to be 1.1 ppb with an upper-bound estimated concentration of 3.3 ppb.” These levels are below the agency’s occupational level of concern of 100 ppb of formaldehyde. The EPA further stated that “the proposed metalworking fluid use pattern is expected to pose little or no environmental exposure. MBM (CONTRAM ST-1) is a reduced risk alternative to formaldehyde releasers currently on the market.”

Unlike competitive products, which are designed for other uses and may re quire the addition of non-ionics and more expensive emulsifiers, CONTRAMST-1 was built specifically for use in metal working fluids. (Lubrizol is the only supplier of biocides designed exclusively for metalworking.) It is exceptionally stable in metalworking fluid concentrates and does not disrupt the balance of the emulsifier system. The result is ease of formulation and reduced complexity for metalworking fluid producers.

The product also demonstrates long lasting efficacy in diluted emulsions; it is not a “one time fix” and it is not added tank side. Instead, it is only registered for use in concentrate. CONTRAM ST-1 lasts throughout the majority of the life of the metalworking fluid, which means longer drain intervals, reduced maintenance costs and much less work tank side. Because operators don’t need to measure and pour biocides into the tank, the opportunity for error—and the dangers of over- or under-treatment—are significantly reduced and human exposure to active biocides is limited.

Proven performance
Developing a high-quality biocide is just the first step. Equally as important is its performance in the finished fluid where it is impacted by other factors including the fluid formulation itself; the use conditions and maintenance practices. CONTRAM ST-1’s wide use globally is the strongest testimony to its performance, but controlled laboratory studies also support the product’s performance benefits.

In studies focused on long-term storage stability and concentrate compatibility, Lubrizol evaluated basic soluble oil formulations; one unprotected (no biocide); one treated with HHT and one treated with CONTRAM ST-1.

Stability of concentrate
There is no guarantee when metalworking concentrate will be used or what the storage conditions will be. Metalworking fluids may be stored for months under extreme temperature s, and it’s critical that they perform as well after six months as they do on day one. To test emulsion stability, formulations of HHT (adjusted to match clear, stable emulsions of CONTRAM ST-1 formulations), CONTRAM ST-1 formulations and a control were tested.

The formulations were:
• Stored at 40° C for extended periods
• Monitored for phase separation and instability
• Checked at regular intervals to confirm emulsions were suitable for use after storage in warm conditions.

Results confirm that CONTRAM ST-1 offers exceptional long term concentrate stability (see Table 1).

Table 1. Concentrate storage stability: emulsion results

*Emulsion results expressed as % oil / % cream separation measured in 5% emulsion after 24 hours.

Biocidal efficacy
Lubrizol used ASTM E 2275, a well-known bacterial challenge, to test the efficacy of its product compared to HHT. Experience shows that all freshly prepared biocide containing products perform well in this method. But again, fluids must provide optimum performance after being in storage for six months or longer. In this test, concentrates were stored for six months at 40° C prior to emulsion preparation and testing. Testing began with 800 mL of fluid added to a quart jar:
• 715 mL metalworking fluid
• 85 mL inoculum
• 10g cast iron chips.

In the standard test, the mixture (see Figure 3) is aerated for five days on and two days off for a total of 12 days. As shown in Table 2, test results indicate that CONTRAM ST-1 maintained its efficacy even in aged concentrates.


Figure 3. ASTM E 2275 mixture.


Emulsions protected with CONTRAM™ ST-1 biocide (green square above) maintain stable pH levels.

Table 2. Bacteria challenge test: aged concentrate results


In addition to the standard test, Lubrizol runs an extended test, stopping only when all emulsions have failed. In the example below, bacterial testing was continued for 13 weeks. Fresh concentrates with a 3% biocide treat rate were diluted to 5%, resulting in 1500 ppm active biocide. The pH of each formulation was monitored throughout the test period. An indicator of bacteria growth, pH goes down as bacteria increase, the result of acidic by-products. Since a high pH creates an unfriendly environment for bacteria, a stable pH of approximately 8 or 9 is critical in a metalworking fluid. Anything lower may result in corrosion issues.

The right choice for metalworking
CONTRAM ST-1 is a new, safer alternative biocide for the US market with exceptional performance properties in metalworking fluids. Backed by an extensive testing and a proven performance history, CONTRAM ST-1 is the right choice for today’s metalworking fluids.