Krytox

Du Pont called this new lubricant material Krytox (64,65) and initially it had such extraordinary properties that it sold for 200/kg ( 187kg ca 1993). Krytox was and is used ia most of the vacuum pumps and diffusion oil pumps for the microelectronics iadustry ia this country and ia Japan because it produces no hydrocarbon (or fluorocarbon) vapor contamination. It has also found important appHcations ia the lubrication of computer tapes and ia other data processiag appHcations as weU as military and space appHcations. 

Information on the production levels of the perfluoroethers and perfluorotertiary amines is not disclosed, but the products are available commercially and are marketed, for instance, as part of the Fluorinert Electronic Liquids family by 3M Co. (17). These Hquids have boiling points of 30—215°C with molecular weights of about 300—800. They range in price from 26—88/kg. Perfluoropropene oxide polyethers are marketed by Du Pont with the trade name Krytox (29). The linear perfluoropropene oxide polyethers are marketed by Daikin under the trade name Demnum (28). The perfluoropolyethers derived from photooxidation are marketed by Montefluos under the trade name of Fomblin (30). These three classes of polyethers are priced from about 100—150/kg. 

Materials of this type have been sold by Du Pont Co. under the Freon E and Krytox trademarks. Perfluorinated materials stmcturaEy similar to those in equation 11 have been prepared by Ausimont by the low temperature irradiation of either hexafluoropropylene or tetrafluoroethylene with oxygen followed by heating and/or irradiation and have been sold as Fomblin Hquids (52). An isomeric polyether, Demnum, prepared by the oligomerization of 2,2,3,3-tetrafluorooxetane followed by fluorination has been commercialized by Daikin (eq. 12). 

In addition to the fluoroplastics and fluororubbers already described other fluoropolymers have been marketed. Polymers of hexafluoropropylene oxide are marketed by Du Pont (Krytox). These materials have a low molecular weight (2000-7000) and are either oils or greases. The oils are uses as lubricants, heat transfer fluids and non-flammable oils for diffusion pumps. The greases are also used as lubricants. They have good heat and oil resistance but it is said that explosions may result from contact with the surfaces aluminium or magnesium cuttings. 

In order to minimize the degradation of macromolecules, the choice of solvent is not a trivial matter. Hydrogen-containing solvents are obviously not suitable, but even halogenated ones such as CFC13 or CC12FCF2C1, usually stable to fluorine, can react violently with this element when irradiated at temperatures near 0°C. We chose two perfluorinated solvents that have been proven safe and suitable for radical fluorination perfluoro-2-(butyl)-tetrahydro-duran (FC-75 Fluorinert from 3M) and hexafluoropropylene oxide (HFPO) oligomers known as Krytox +... 

Fluorination of low-molecular-weight linear oligomers 7 (n = 7-12) also proceeded cleanly. In this case Krytox was found to be a better solvent because of solubility problems encountered with FC-75. The product 11 was obtained in very good yield, and both H-NMR (which shows no signals) and 19F-NMR are in accord with essentially complete replacement of all the hydrogen atoms by fluorine. That little fragmentation occurred was shown by GPC analysis (M. 3200). 

Mixtures of 25-30% fluorine diluted with nitrogen were used in this work. The gas mixtures were prepared in a secondary container. The appropriate polyether was dissolved either in perfluoro-2-butyl-THF (FC-75) or in Krytox GPL 100 (a fluorinated oil), which also contained about 5 g of pulverized NaF to absorb the relased HE The reaction mixture was cooled to - 10°C, stirred with the aid of a vibromixer and irradiated with a 450-W medium-pressure mercury lamp. A stream of fluorine in nitrogen (ca. 140 ml/min) was passed into the mixture such that the temperature did not rise above +10°C. The reaction was stopped after 200 mmol of fluorine had been passed through. The mixture was poured into water and the organic layer was washed with sodium bicarbonate solution. The water layer was extracted twice with CFCL. The combined fluorocarbon fractions were washed with water, dried with MgS04, and filtered, and the solvent was removed under reduced pressure. 

Perfluoropolyethers emerged on the market in the early 1970s. The first perfluoropolyether was the homopolymer of hexafluoropropylene oxide produced by DuPont, which has the structure [—CF2CF(CF3)0—] and this new lubricant material was called Krytox.31,32 Krytox was and is used in most of the vacuum pumps and diffusion oil pumps for the microelectronics industry because it does not produce any hydrocarbon or fluorocarbon vapor contamination. It also has important applications in the lubrication of computer tapes and in other data processing as well as military and space applications. 

CF20—)m (—CF2CF20—) . This fluoropolymer has better low-temperature properties than Krytox, but is more expensive. Fomblin Z is made by photochemical polymerization of a mixture of oxygen and tetrafluoroethylene to prepare the random copolymer. The methylene oxide unit (—CF20—) imparts even more extraordinary low-temperature properties than those derived from vibration and free rotation of other perfluoroether linkages. 

Perfluoropolyethers have found widespread use as high-performance lubricants and several companies manufacture a range of these materials (Krytox , Du Pont Fomblin , Montefluos Demnum , Daikin). The Fomblin fluids and Krytox require the use of fluorine in the finishing stages [81] whilst Demnum is synthesised by polymerisation of the fluorooxetane 16 followed by per-fluorination using fluorine (Fig. 27) [82]. 

Krytox - pLUORINECOMPOUNDS,ORGANIC - DIRECTFLUORINATION] (Vol 11) - pLUORINECOMPOUNDS,ORGANIC - FLUOROETHERS AND FLUOROAMINES] (Vol 11)... 

The extrapolation of this work has led to KRYTOX products commercially available by the Dupont Company [59-61]. 

Thus, even if their properties at high temperatures are still very good, this is not so at low temperatures because of their high Tg or their high crystallinity. However, the polyethers for which the C —O—C bands bring free spinning and decrease the hardness of the perhalogenated —C—C sequence are exceptions. These are the Fomblin polyethers from Montefluos and the Krytox ones from Du Pont De Nemours. However, for these products, problems of solubility and reactivity are observed. 

From perfluoroepoxypropylene, Moore [37, 38] obtained polyethers and products manufactured under the trade name Krytox [39,40] by Du Pont De Nemours. 

Krytox seems like a product from heaven, as many of its attributes are spectacular. It is a fluorinated grease and is therefore impervious to hydrocarbon- and water-based solvents. It cannot bum, so it has no flash point and can be exposed directly to oxygen, even at high pressures. It can be used over the widest temperature range of all the greases and works equally well with stopcocks as with joints. It has remarkable stability characteristics and can withstand long-term abuse. Best of all, Krytox greases are nontoxic. 

Krytox DF stands for Krytox Dry Film. It was previously known as Vydax. 

Krytox from these surfaces requires rough scrubbing with a toothbrush or fingernail brush and also requires sufficient solvent to remove the material. 

Krytox, Teflon, and other similar products can be removed by incineration, and the amount of fluorine released from several stopcocks or joints is a relatively small amount. However, if the oven used is not properly vented in the confined... 

Fluorocarbon greases (Krytox) originally required a chlorinated fluorocarbon for removal. In the last few years, it was found that an industrial solvent (such as BH-38 from Spartan Chemical Co. ) can remove Krytox. Tests that this author has conducted seem to show a film of some kind remains on the joint, so it is unknown exactly how safe it is to heat a joint or stopcock that has been cleaned with this technique. Do not use heat to remove Krytox because heating (> 260°C) will produce fumes (lethal fluorine compounds, such as HF) that are highly toxic. For more information on cleaning these greases, see Sec. 3.3.3. 

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