Two years ago, 3M voluntarily phased out substances that contained perfluorooctanyl groups, a chemical component of previously commercialized fluorosurfactants. The company immediately began developing alternative chemistries that could meet or exceed customer needs. The company's researchers worked toward solutions that had both the performance factors customers expect, as well as an improved environmental profile. Two alternative products - 3M(tm) Fluorad(tm) fluorosurfactants FC-4430 and FC-4432 - were sampled to the coatings industry.

Two New Solutions

"These two new fluorosurfactants have exceeded our performance expectations and are gaining customer acceptance in a variety of applications," said Dr. Michael Terrazas, research specialist, 3M Performance Materials Division. "Originally intended to be an FC-430 replacement, data is showing the versatility of these fluorosurfactants in applications that formerly used other nonionic fluorosurfactants, and have even found some success in aqueous applications that previously had used anionic fluorosurfactants."

Based on an entirely new fluorochemical building block, FC-4430 and FC-4432 are high-molecular-weight polymers that show the same performance benefits that have long differentiated fluorochemicals from competing surfactant technologies, such as silicones and hydrocarbons. The company believes this stems from the physical properties of the fluorochemical component of these materials. Very little product is necessary to afford a significant surface tension reduction of a formulation, which for customers means low use levels. Hydrocarbons, in contrast, often require an order of magnitude more product to significantly reduce surface tensions, and the surface tension levels reached do not approach those possible with FC-4430 or FC-4432.

Second-coat adhesion can often be adversely affected when using silicone or conventional fluorochemical surfactants. However, this has not been observed when using FC-4430 or FC-4432, even at higher loading levels. This is due to the shorter fluoroalkyl chain length incorporated into these new materials.

Overall, the performance of the fluorosurfactants has been exceptional. Customers report excellent leveling/wetting and improved flow even in harsh conditions; good smoothing of high-gloss coatings in the automotive and aerospace industries; and superior coatings in industrial-maintenance products for use on wood, metals and plastics.

Getting to this point has been a story of perseverance.

A Century of Innovation

When the company decided to reformulate its Fluorad fluorosurfactant line, numerous ideas were already forming in the minds of 3M scientists. The final choice of molecules, however, would depend upon three factors.

1. Sustainable technology that stands the test of time. Long-term sustainability is key to developing viable products and applications. Researchers turned to technology platforms that had a proven track record - electrochemical fluorination (ECF).

2. The new building block had to be versatile enough to provide good performance in a variety of applications. "Because we were looking to replace an entire family of materials, the base chemistry had to provide good performance across a range of industries and in a number of different applications," said Dr. Larry Wendling, vice president, 3M Performance Materials Division.

3. It must have a good EHS&R profile. The environmental landscape and regulations continue to change.

Using ECF, a number of shorter chain length prototype molecules were created. After experimentations and testing were completed, the perfluorobutyl (PFB) chemical component was chosen as the building block molecule for the surfactants (a four-carbon perfluorinated group). "We investigated the use of even shorter chained fluorochemicals such as perfluoromethyl and perfluoroethyl," said Terrazas, "but found they could not provide the performance the industry demanded. Perfluorobutyl moieties simply struck the best balance between high performance, low toxicity and environmental acceptability."

Environmental, Health, Safety & Regulatory (EHS&R)

Before the company would release any product for sampling or sale, environmental fate and effects testing was conducted on the ultimate degradation product of the residuals present in the product - perfluorobutane sulfonate (PFBS). The toxicological profiles of the compound were assessed, including mammalian toxicity, chronic mammalian toxicity, bioconcentration factor and persistence. The PFBS environmental and safety summary shows the substance has a very low order of toxicity as determined by a range of toxicity studies. These test findings indicate the substance would not be considered bioaccumulative or toxic (BT) under the U.S. EPA's PBT chemical policy.

The new PFB formulation behaved largely as predicted, demonstrating an excellent environmental profile.