FLUOROCHEMICAL

Fluorine and its compounds are used in producing uranium (from the hexafluoride) and more than 100 commercial fluorochemicals, including many well known high-temperature plastics. Hydrofluoric acid etches the glass of light bulbs, etc. Fluorochlorohydrocarbons are extensively used in air conditioning and refrigeration. 

Fluorine reacts with the halogens and antimony to produce several compounds of commercial importance antimony pentafluoride [7783-70-2J, bromine trifluoride [7787-71 chlorine trifluoride [7790-91 -2J, and iodine pentafluoride [7783-66-6J. Chlorine trifluoride is used in the processing of UF (see Uraniumand uranium compounds). Bromine trifluoride is used in chemical cutting by the oil well industry (see Petroleum). Antimony and iodine pentafluorides are used as selective fluorinating agents to produce fluorochemical intermediates (see Fluorine compounds, inorganic). 

Cobalt difluoride, used primarily for the manufacture of cobalt trifluoride, CoF, is available from Advance Research Chemicals, Inc., Aldrich Chemicals, and PCR in the United States, Fluorochem in the UK, and Schuhardt in Germany. The 1993 price varied from 60 to 200/kg depending on the quantity and the price of cobalt metal. C0F2 is shipped as a corrosive and toxic material in DOT-approved containers. 

Historically, the annual consumption of nickel fluoride was on the order of a few metric tons. Usage is droppiag because nickel fluoride is Hsted ia the EPA and TSCA s toxic substance iaventory. Nickel fluoride tetrahydrate is packaged ia 200—500-lb (90.7—227-kg) dmms and the 1993 price was 22/kg. Small quantities for research and pilot-plant work are available from Advance Research Chemicals, Aldrich Chemicals, Johnson/Matthey, Pfalt2 and Bauer, PCR, and Strem Chemicals of the United States, Fluorochem of the United Kingdom, and Morita of Japan. 

Another impetus to expansion of this field was the advent of World War 11 and the development of the atomic bomb. The desired isotope of uranium, in the form of UF was prepared by a gaseous diffusion separation process of the mixed isotopes (see Fluorine). UF is extremely reactive and required contact with inert organic materials as process seals and greases. The wartime Manhattan Project successfully developed a family of stable materials for UF service. These early materials later evolved into the current fluorochemical and fluoropolymer materials industry. A detailed description of the fluorine research performed on the Manhattan Project has been pubUshed (2). 

Health and Safety Factors. Completely fluorinated alkanes are essentially nontoxic (16). Rats exposed for four hours to 80% perfluorocyclobutane and 20% oxygen showed only slight effects on respiration, but no pathological changes in organs. However, some fluorochemicals, especially functionalized derivatives and fluoroolefins, can be lethal. Monofluoroacetic acid and perfluoroisobutylene [382-21-8] are notoriously toxic (16). 

Several excellent review articles (28—31) cover the chemistry of the acid and its derivatives in great detail. Trifluoromethanesulfonic acid is available from the 3M Co. as Fluorochemical Acid FC-24 the lithium salt is available as Fluorochemical Specialties FC-122, FC-123, and FC-124 (32). 

Fluorad Fluorochemical Specialties FC-740, Minnesota Mining Manufacturing Co., St. Paul, Minn., 1987. 

Fluorochemicals repel both water and oU because they produce an extremely low energy surface (18—26). The effectiveness of the fluorochemicals depends upon uniform surface coverage and orientation of the molecules on the fiber surface so that the perfluoroalkyl chains are directed away from the surface. The result is a GST as low as 5—10 mN /m (dyne/cm). Fluorochemical finishes are often formulated with nonfluorinated resin-based water-repeUent extenders. These water repeUents not only reduce the cost of the finish but may also improve durabUity (27,28). 

Quarpel is an important combination of fluorochemical finish and resin-based extender developed by the U.S. Army Natick Laboratories for military use. This finish typicaUy contains 4—6 wt % commercial fluorochemical emulsion, 4—6 wt % resin-based repeUent emulsion, 0.1 wt % acetic acid, and 5 wt % isopropyl alcohol. If necessary, the formulation includes a catalyst to cross-link the resin-based component. Quarpel specifications demand exceUent initial water and oU repeUency and exceUent durabUity to washing and dry cleaning. 

Fluorochemical repeUents are commercially avaUable as emulsions or solvent solutions. The most widely used emulsions for fabrics and carpet are cationic, but nonionic emulsions are becoming more prevalent. The emulsifier in the formulation can affect the repeUency and durabUity of the product (28). Surfactants used in the fluorochemical emulsions or added to finish baths should be nonrewetting and have a minimum adverse effect on oU repeUency. Solvent solutions of fluorochemicals are becoming less common as a result of toxicity and environmental concerns. 

The choice of appHcation conditions for fluorochemical repeUents depends on the textile, the repeUent formulation, and level of repeUency required. SuppHers provide detaUed recommendations in their product buUetins. Where a high level of repeUency is required or the generaUy somewhat higher cost is... 

Many fluorochemical finishes for fabrics require curing at up to about 175°C. Curing aUows melt-spreading of the fluorochemical to ensure maximum leveling of the finish on the fibers and to promote optimum orientation of the pendant fluorinated portion of the molecules on the fibers. 

Silicones. SUicones are exceeded only by fluorochemicals in the volume used as repeUents for textiles. They are widely used on ceUulosic and synthetic fiber fabrics. SUicones provide water-based stain resistance good durabUity to washing improved tear strength a soft, sUck hand and improved fabric sewabUity. 

The water repeUency of sUicone finishes results from the low CST (ca 22 mN/m or dyne/cm) produced by the methyl groups in the sUicone that are oriented away from the fiber surface. The CST is lower than that produced by any class of compounds except for fluorochemicals. 

Resin-based repeUents may be used alone or in combination with durable-press resins. They are widely used as extenders for fluorochemical repeUents. When used alone, several of the resin-based finishes require an acid catalyst and curing at temperatures above 150°C for maximum repeUency and durabUity. When coappUed with durable-press finishes, which themselves require a magnesium chloride catalyst, the catalyst and curing conditions for the durable-press finish provide the necessary conditions for the repeUent. 

Waxes and Wax—Metal Emulsions. Waxes and wax—metal emulsions are the lowest priced, widely used water repeUents and fluorochemical extenders. They can be appUed by padding or exhaustion with no cure commonly required. However, waxes have only poor-to-fair durabUity to washing and dry cleaning, and tend to show streaks from abrasion. 

Carpet. Carpet, an important textile, may also be treated to provide water and oU repeUency however, the principal functions of the current carpet treatments are to provide soU and stain resistance. High quaUty carpets, especiaUy those made from nylon, polyester, or wool, have a significant proportion of the surface coated with fluorochemical materials. The treatments can be spray-appUed to a finished carpet or appUed directly to the fiber during the spinning or dyeing operations. Suitable fluorinated resin materials are readily avaUable from 3M or DuPont. 

Standard Test 80.7-92). Suppliers of fluorochemical repellents may recommend different times or a different series of hydrocarbons ia the evaluation of treated fabrics. 

Chrome-complexed fluorochemicals, as weU as fluoropolymers, are widely used products. The compositions are proprietary. Fluorochemicals provide a high degree of water repeUency as weU as repeUency to aqueous stains, oUs, grease, and oilhorne stains. TraditionaUy, treatments are appUed duting a dmm process ia which about 30 min are required for flUl penetration of the leather to occur. Products are also avaUable for appUcation with sprayiag equipment and roU coaters. 

The 3M Abrasion Test (51) is used to assess the durabUity of a protective fluorochemical finish by evaluating its resistance to abrasion and wear. The surface is abraded with an AATCC crockmeter fitted with sandpaper. 

Oil Repellent. Fluorochemicals are the only class of material that can provide oil repeUency without altering the porosity of the paper or paperboard. Physical barriers to oil penetration are used primarily for their moisture- or gas-barrier properties, with retarded oil penetration as a secondary benefit. The most common od-repeUent additives are long-chain perfluoroalkyl phosphate salts of ammonia or diethanol amine. Commercial sources include Scotchban (3M), Zonyl (DuPont), and Lodyne (Ciba Specialties). There are also a fluorochemical carboxylate salt, Lodyne (Ciba Specialties), and fluorochemical copolymers, eg, Scotchban (3M). The widest range of oily fluid holdout is provided by the fluorochemical copolymers. 

---