AU634982B2 - Perfluoropolyethers - Google Patents

Description

OPI DATE 29/11/90 AOJP DATE 10/01/91 INTERNAl APPLN. ID 43311 89 PCT NUMBER PCT/US89/01861 'REATY (PCT) (51) International Patent Classification 5 (11) International Publication Number: WO 90/13583 C08G 2/30, 65/30 Al 8G 2/30, 65/30 A (43) International Publication Date: 15 November 1990(15.11.90) (21) International Application Number: PCT/US89/01861 (81) Designated States: AT (European patent), AU, BE (Europear patent), BR, CH (European patent), DE (European (22) International Filing Date: 2 May 1989 (02.05.89) patent), FR (European patent), GB (European patent), IT (European patent), JP, KR, LU (European patent), NL (European patent), SE (European patent).

(71)Applicant: EXFLUOR RESEARCH CORPORATION [US/US]; 8868 Research Boulevard, Suite 206, Austin, TX 78758 Published With international search report.

(72)Inventors: LAGOW, Richard, J. 100 Navajo Trail, Georgetown, TX 78628 BIERSCHENK, Thomas, R. 1803 Chincoteague, Roundrock, TX 78681 (US).

JUHLKE, Timothy, J. 2106 Windsong Trail, Roundrock, TX 78664 (US).

(74) Agents: DeCONTI, Giulio, Jr. et al.; Hamilton, Brook, 6-.

Smith Reynolds, Two Militia Drive, Lexington, MA 02173 (US).

(54) Title: PERFLUOROPOLYETHERS (57) Abstract Perfluoropolyethers containing high concentrations of difluoromethylene oxide units in the polymer chain are disclosed.

See back of page WO 90/13583 PCY/US89/01861 -1-

PERFLUOROPOLYETHERS

Field of the Invention This invention is in the fields of polymer and fluorine chemistry.

Background of the Invention Perfluoropolyethers have long been recognized for their outstanding thermal properties and their wide liquid ranges. These properties render them useful as hydraulic fluids, heat exchange fluids and lubricants. For many applications, it is desirable to have a fluid with very good low temperature properties low pour points) as well as good high temperature stability. It is recognized in the art that one way of extending the low temperature liquid range of a fluid is the incorporation of methylene oxide units in the polymer. The low energy of activation for rotation about a carbon-oxygen bond gives the fluid added mobility at low temperatures.

Unfortunately, typical vinyl polymerization techniques such as those used to make polytetrafluoroethylene oxide and polyhexafluoropropylene oxide (DuPont Krytox

TM

cannot be used to make a difluoromethylene oxide contairing polymer.

Sionesi and coworkers describe the synthesis of polymers of the general formulae CF 3

-O-(CF

2 -O)n -CF2-C(O)F, CF 3

-(O-CF

2 )n -CF 2 -C(O)F and CF 3

-(O-CF

2 n 2,.

WO 90/13583 PCT/US89/01861 1 -2- See French patents 1,531,902 and 1,545,639. The polymeric mixture was obtained by reacting difluorocarbene (generated in situ by the pyrolysis of hexafluoropropene) with molecular oxygen. Although the polymers contain reactive end groups such as acyl fluoride and fluoroformate groups which limit their stability, the polymers represented a major breakthrough.

Gerhardt and Lagow describe the synthesis of perfluoropolyethylene oxide by direct fluorination.

J. Chem. Soc., Perkin Trans. I, 1321 (1981). The authors also report the formation of a partially fluorinated polymer obtained in low yield when polymethylene oxide (polyformaldehyde) was slowly reacted with dilute elemental fluorine at -78'C.

Disclosure of the Invention This invention pertains to perfluoropolyethers which contain high concentrations of difluoromethylene oxide units in the polymer chain and which are capped with unreactive trifluoromethyl terminal groups and to method of producing such perfluoropolyethers. The perfluoroethers which can be produced by the method of this invention have a chain structure consisting essentially of repeating units -OCF 2 and wherein Y is selected from -CF2-, -CF2CF2-, -CF2CF2CF-, -CF(CF3)CF2-, -CF2CF2CF 2CF2 -CF(C 2

F

5 )CF2, -CF 2 CF2-O-CF 2

CF

2 and

-CF

2

CF(CF

2 the repeating units being randomly distributed WO 90/13583 PCT/US89/01861 -3along the chain, the ratio of -OCF 2 units to -OYunits being greater than 1 and less than about 100.

The perfluoropolyethers have perfluoroalkyl end groups. The perfluoropolyethers have a molecular weight from about 300 to about 50,000 atomic mass units. The polymers include homopolymers containing essentially 100% difluoromethylene oxide units (i.e.

perfluoropolymethylene oxide) and copolymers containing difluoromethylene oxide units to tetrafluoro-ethylene oxide, perfluoropropylene oxide or perfluorobutylene oxide units in a ratio of from about 100 down to just greater than 1. The polymers range in molecular weight from about 300 amu to about 50,000 amu. The higher molecular weight polymers are solids; th*alower molecular weight polymers are Inr p reR r e .e fluids. 'fepolymers contain a hydrogen content below 5 ppm and can be prepared in 20 to 90% yield depending on the composition of the polymer being fluorinated. The polymers are synthesized by perfluorinating, preferably in the presence of a hydrogen fluoride scavenger such as sodium fluoride, polymers which contain at least one ethylene oxide, diethylene oxide, propylene oxide, butylene oxide or epichlorohydrin for every 100 methylene oxide units along the polymer chain.

Novel perfluoropolyethers which can be produced by the method of this invention are represented by the formula: Rf 1 (OCF 2)n (OY)m- ORf 2 WO 90/13583 PCT/US89/01861 -4wherein Y can be -CF 2

CF

2

CF

2

-CF

2

CF

2

CF

2

CF

2

-CF(C

2

F

5

)CF

2

-CF

2

CF

2

OCF

2

CF

2 or -CF 2

CF(CF

2 C1)-; wherein Rfl and Rf 2 may be the same or different and are selected from CF 3

C

2

F

5

C

3

F

7

C

4

F

9

C

2

F

4 C1 and

C

3

F

6 Cl and wherein n is an integer greater than 1 and m is an integer equal to or greater than 1 such that the ratio n/m is from greater than 1 but less than about 100. The repeat units (OCF 2 and (OY) are randomly distributed in the polymer chain. The perfluoropolyether fluids of this invention are useful as hydraulic fluids, as heat transfer media or as bases for high performance greases which require fluids having a wide liquid range. The perfluoropolyether solids are useful as moldable elastomers or grease fillers. In addition, the solid polymers can be broken down, for example, by pyrolysis at 600'C, to produce low molecular weight fluids.

Best Mode of Carrying Out the Invention The perfluoropolyethers which can be produced by the method of this invention comprise the homopolymer perfluoropolymethylene oxide and perfluorinated copolymers of methylene oxide and either ethylene oxide, diethylene oxide, propylene oxide, butylene oxide or epichlorohydrin wherein the ratio of methylene oxide units to ethylene oxide, diethylene oxide, propylene oxide, butylene or epichlorohydrin oxide ranges from greater than WO 90/13583 PC/US9/1861 1 and less than about 100. The perfluoropolyethers are defined by the formula: Rf 1

(OCF

2 n (OY)m ORf 2 wherein Y is -CF 2 -CF2CF 2

-CF

2

CF

2

CF

2 -CF(CF3)CF2-, -CF2CF2CF2CF

-CF(C

2

F

5

)CF

2 -CF2CF OCF2CF 2 or -CF 2

CF(CF

2 wherein Rfl and Rf 2 may be the same or different and are selected from CF 3

C

2

F

5

C

3

F

7

C

4

F

9

C

2

F

4 Cl and C 3

F

6 Cland wherein n is an integer greater than 1 and mmay-b -e an integer equal to or greater than 1 such that the ratio of n/m is greater than 1 but less than about 100. The polymers range from about 300 to about 50,000 amu in size, vhe high molecular weight polymer being solids and the intermediate and lower molecular weight polymer being fluids. The polymers contain no reactive perfluoroalkyl end groups.

Compounds wherein Y is CF2CF2CF 2 -CF2CF2CF2CF2-

-CF(C

2

F

5

)CF

2

-CF

2 CF2OCF 2 CF and -CF 2

CF(CF

2 Cl)are new structures.

The perfluoropolyethers are synthesized by selecting or synthesizing a starting hydrocarbon polyether which contains methylene oxide units and the desired amount of ethylene oxide, diethylene oxide, propylene oxide, butylene oxide, epichlorohydrin units and subsequently perfluorinating the polymer under controlled conditions, preferably in 5147 k2Y-r WO 90/13583 PCT/US89/01861 -6the presence of a sodium fluoride scavenger such as sodium fluoride or potassium fluoride. The hydrocarbon starting material must have at least one ethylene oxide, propylene oxide or butylene oxide unit for about every one hundred methylene oxide units along the polymer chain.

The type of perfluoropolymer product, and its molecular weight, depend on the composition of starting hydrocarbon polyether and the fluorination conditions. The hydrocarbon starting material can be selected from commercially available polymers such as

CELCON

TM (Celanese Corp.) which contains about a 55/1 ratio of methylene oxide units to ethylene oxide units. Alternatively, the starting polymers can be synthesized. Ethylene oxide-methylene oxide copolymers can be prepared with the desired ratio of comonomers by polymerization of 1,3-dioxolane/ trioxane mixtures using a trifluoromethane sulfonic acid catalyst. Polymers of methylene oxide and propylene oxide or butylene oxide can be prepared for fluorination. For example, polymerization of trioxane and 4-methyl-i, 3-dioxolane gives a copolymer of methylene oxide and propylene oxide.

Similarly, copolymers of methylene oxide and diethylene oxide can be made by copolymerizing trioxane with 1,3,6, trioxocane.

The conditions of fluorination are important to the ultimate product. High fluorine concentrations, fast flow rates and elevated temperatures each favor fragmentation, and thus lower molecular WO 90/13583 PCr/US89/01861 -7weight products can be obtained. Milder fluorination conditions designed to prevent fragmentation give stable high molecular weight perfluoropolyethers.

Although a variety of fluorinating agents such as CIF 3 and BrF 3 could be used to fluorinate the hydrocarbon polymer, elemental fluorine is the reagent of choice. Typically, low fluorine concentrations between one and te percent are used initially. Upon approaching perfluorination, the polymer is exposed to pure fluorine first at room temperature then at 100'C. The best results are obtained when a hydrogen fluoride scavenger, such as sodium fluoride, is placed in the fluorination reactor along with the polymer. The fluorination of ethers in the presence of hydrogen scavengers is A, 755,:517°.nck 4 jT'5774 described in United States Patents pplication Serial m W entitled "Perfluorination of Ethers in the Presence of Hydrogen Fluoride Scavengers", f1 r the teachings of which are incorporated by reference herein.

When mild fluorination conditions are used to fluorinate a high molecular weight polymer (greater than 10,000 amu), a white solid is typically obtained. Several schemes can be employed to prepare intermediate molecular weight fluids.

Perfluorination of a low molecular weight polymer using mild fluorination conditions works well.

Treating a higher molecular weight polymer with slightly harsher fluorination conditions can lead to fluids when the conditions are chosen to

L.IL~

irn- I~~w WO 90/13583 PCI/US89/01861 -8give a controlled amount of chain cleavage.

"Perfluorination" of a high molecular weight polymer using mild conditions can be used to replace a specified number of hydrogens with fluorine. A second step, the fragmentation step, is designed to promote chain cleavage. Elevated temperatures and high fluorine concentrations are used to give the perfluoropolyether fluid.

An alternate scheme, and possibly the method of choice for preparing a wide range of molecular weights involves the fluorination of high weight polymer using mild fluorination conditions to give a high molecular weight solid containing both perfluoro alkyl and acyl fluoride end groups.

Treatment of the polymer with pure fluorine at elevated temperatures (100'C) gives a polymer containing only perfluoro alkyl end groups. The high molecular weight solids can be broken down to lower molecular weight components by pyrolysis. The procedure is dedsribed in United States Patents Sa.M.n-tS LN entitled "The Pyrolysis of Perfluoropolyethers", 1hf hi- bi -r which a- :-ne--rprnta- hy E Thereafter, pyrolysis of the solid in the presence of nitrogen, air or fluorine gives lower molecular weight polymers (fluids). By selecting the proper pyrolysis temperature (400-500'C) and by carrying out the pyrolysis in a distillation-type apparatus, a well defined boiling point range can be collected while less WO 90/13583 PCr/US89/01861 -9volatile components are returned to the high temperature portion of the apparatus to be further fragmented. If the pyrolysis is not carried out in the presence of fluorine, an additional fluorination at elevated temperature is needed to remove the acyl fluoride terminal groups generated during the cracking.

For preparation of difluoromethylene oxide, inclusion of the 2-4 carbon comonomer in the starting hydrocarbon polymer is believed to prevent depolymerization of the polymer during the fluorination procedure. For example, when pure, high molecular weight polymethylene oxide is fluorinated, no perfluorpolymethylene oxide is obtained. Carbonyl fluoride is made instead. The reasons for this is that when a high molecular weight polymer (greater than 10,000 amu) is fluorinated, the likelihood of breaking at least one carbon-oxygen bond along the polymer chain in the course of fluorination is essentially 100%. When bond cleavage occurs, the polymer is believed to depolymerize or "unzip" giving rise to carbonyl fluoride as the sole product.

By randomly incorporating at least one ethylene oxide for every 100 methylene oxide units, perfluoromethylene oxide yields in the 20 to range can be obtained. The ethylene oxide unit is thought to provide a point of termination for the "unzipping" reaction. The ethylene oxide also provides a stable trifluoromethyl terminal group for the polymer. By doubling the molar concentration of ethylene oxide from 2% to the WO 90/13583 PC/US89/01861 yield of perfluoropolymer is increa, from 40% to Slightly higher concentrations give increasingly higher yields of perfluoromethylene oxide.

A preferred method of elemental fluorination for production of perfluoropolymethylene oxide is as follows. The starting hydrocarbon polyether is ground to a fine powder and mixed with powdered sodium fluoride (approximately 5/1 ratio of NaF to polymer). The blend is dried under a stream of inert gas nitrogen). The blend is then exposed to a stream of fluorine gas diluted with an inert gas (nitrogen or helium). This initial fluorine concentration should be about 1% with a fluorine flow rate of about Icc/min/gram polymer. The temperature is held at 0'C. These conditions are maintained for about 2 days after which the inert gas concentration is reduced by 50% to give a 2% fluorine content.

After about 6 hours, fluorine concentration is raised to 10%. Over a period of 48-56 hours, fluorine concentration can be raised stepwise until the pure fuorine conditions are attained. The pure fluorine stream is maintained for about 4 hours to give a perfluorinated product. The product is then cooled.

The product can be removed from NaF by dissolution in Freon 113.

The perfluoropolyether fluids of this invention have several distinct advantages over the existing fluids, namely Fomblin ZTM fluids. Polymers can be prepared which contain essentially 100% methylene In oxide units instead of 50-60% WO 90/13583 PC/US89/01861 -11methylene units which is typical of the Italian product. These polymers exhibit far superior low temperature properties and have viscosities which are extremely independent of temperature. Low pour points are needed for many cryogenic and space applications.

The invention is further illustrated by the following examples.

Example 1. Production of Perfluoropolymethylene oxide.

200 grams of high molecular weight (10,000) polymethylene oxide which contains four mole percent ethylene oxide was prepared by copolymerizing 1,3,5-trioxane (2.8 mole) and 1,3-dioxolane (0.3 mole) using a trifluoromethane sulfonic acid catalyst -3 (2.6x10- mole). The finely divided powder obtained was dried at room temperature for 12 hours using a stream of nitrogen gas. The powder was mixed with 1,000 grams of NaF powder in a conical shaped nickel reactor which was rotated at a frequency of revolutions per minute. After purging the reactor with 4 L/min. nitrogen for several hours, the fluorine was set a 200 cc/min while the nitrogen flow was set a 5 L/min. After 48 hours, the nitrogen flow was reduced to 2.5 L/min. and was kept there for an additional 6 hours before exposing the polymer to pure fluorine. Following exposure of the polymer to pure fluorine for several hours at ambient temperature, the polymer was reacted with WO 90/13583 PC/US89/01861 -12fluorine at 100'C to decarboxylate any acyl fluoride end groups to give trifluoromethyl terminated groups.

Typically, a flow of 50 cc/min. of pure fluorine for 6 hours is sufficient to remove all of the unwanted end groups. The perfluoro product was separated from the NaF/NaHF 2 powder by dissolving the NaF in water.

Approximately 210 grams of a solid white was obtained.

Approximately 75g of a medium viscosity oil was extracted from the solid with freon 113 solvent. The 19 fluid was characterized by 1F NMR. Each of the individual spectral lines were assigned a structure by comparison with the spectra of known perfluoro compounds. Spectral data for the fluid is given in the table below.

Table 1 Structure Chemical Relative Shift (ppm) Intensity

-OCF

2 CF2OCF OCF2CFO-

-OCF

2

OCF

2

OCF

2

CF

2 O- 55.1 7.3 -OCF OCF OCF 2 57.0 73.0 CF OCF 0- 57.4 7.3 CF OCF 0- 59.7 11.8 -OCF CF OCF CF O- 90.7 1.4 -OCF2OCF 2

CF

2 0- 92.5 2.8 WO 90/13583 PCT/US89/01861 -13- On the basis of the NMR Spectroscopic analysis, the fluid was determined to be polydifluoromethylene oxide containing approximately 2 mole percent tetrafluoroethylene oxide.

Example 2 200g of high molecular weight (10,000) poly(ethylene oxide-methylene oxide) copolymer which contained fourteen mole percent ethylene oxide was prepared in a manner similar to that used for preparing the polymer of Example 1. 1,3-dioxolane (0.6 mole) is mixed with trioxane (1.75 moles) in a methylene chloride solvent. A white precipitate forms upon adding the trifluoromethane sulfonic acid -3 catalyst (2.6x10-3 mole). The finely divided powder obtained was dried at room temperature for twelve hours using a stream of nitrogen. The powder was mixed with 100g of NaF powder in a conical shaped nickel reactor which was rotated at a frequency of five revolutions per minute. The polymer was fluorinated using conditions identical to those employed for the fluorination of the polymethylene oxide polymer containing four mole percent ethylene oxide (Example Approximately 260 grams of white elastomeric solid was obtained upon dissolving the sodium fluoride/bifluoride in water.

Extraction of the solid with freon 113 gave of a freon soluble oil which was characterized by 19

F

NMR as above.

WO 90/13583 PCT/US89/01861 -14- Table 2 Structure Chemical Relative Shift (ppm) Intensity -OCF CF OCF OCF CF 0- 53.8 2.9 -OCF OCF OCF 2

CF

2 55.3 8.3 -OCF OCF OCF 0- 56.8 54.1 CF OCF O- 57.5 CF OCF 0- 59.8 12.4

-OCF

2 CF2OCF 2 CF 0- 91.0 1.2 -OCF OCF CF 0- 92.7 8.3 Based upon the NMR Spectrum, the fluid was determined to be a copolymer of difluoromethylene oxide (DFMO) and tetrafluoroethylene (TFEO) oxide in which the molar ratio DFMO to TFEO units was essentially the same as the molar ratio of the methylene to ethylene units in the starting polymer (94/6 based upon 19F NMR). Distillation of the product yielded the following fractions: a fraction (20.1g) boiling between 150 and 210'C at 100mm Hg and having a pour point of -133'C and an ASTM slope of 0.72; a second fraction (18.0g) boiling between 210'C at 100mm Hg and 223'C at 15 mm Hg having a pour point of -120'C and an ASTM slope of 0.63; a third fraction (19.3g) boiling between 223'C at 15 mm Hg and 275'C at 100 Hg having a pour point of -115"C and an ASTM slope of 0.55; a fourth fraction (15.3g) boiling between WO 90/13583 PCT/US89/01861 275'C and 335'C at 60 Hg having a pour point of -112"C and an ASTM slope of 0.43 and a residue (22.2g) having a pour point of -107'C and an ASTM slope of 0.36.

Example 3 of a high molecular weight (20,000) poly(ethylene oxide-methylene oxide) copolymer containing 0.5 mole percent ethylene oxide was mixed with 140g of NaF powder and loaded in a small fluorination reactor. The reactor was cooled to and a gas flow of 20 cc/min fluorine and 100 cc/min nitrogen was maintained for 24 hours. Next, the temperature was raised to O'C while the gas flows were held at their initial settings for an additional 24 hours. The nitrogen flow was then decreased to cc/min with a reactor temperature of +10'C for 12 hours. Finally, the polymer was treated at room temperature for six hours with pure fluorine. The perfluoro product was separated from the NaF/NaHF 2 powder by dissolving the salt in water. Approximately llg of a fine white powder was obtained.

Example 4 200g of a high molecular weight polymethylene oxide which contained six mole percent propylene oxide was prepared by copolymerizing 1,3,5-trioxane and 4-methyl-1,3-dioxolane using a trifluoromethane sulfonic acid catalyst. The finely divided powder obtained was dried at room WO 90/13583 PCT/US89/01 861 -16temperature for 12 hours using a stream of nitrogen gas. The powder was mixed with 1,200g of NaF powder in a conical shaped nickel reactor which was rotated at a frequency of 5 revolutions per minute. After purging the reactor with several volumes of nitrogen, the fluorine flow was set at 200 cc/min while the nitrogen flow was set at 5 L/min. These conditions were maintained for 48 hours (reactor temperature: at which time the nitrogen flow was reduced to 2.5 liters per minute and was kept there for an additional 6 hours before exposing the polymer to pure fluorine. Following exposure of the polymer to pure fluorine for 6 hours at ambient temperature, the polymer was treated with pure fluorine at 110'C for 4 hours. The reactor products were washed with several gallons of water leaving behind 240g of a white 19 powder identified by 1F nmr as a perfluoro(methylene oxide-propylene oxide) copolymer.

Example A copolymer of methylene oxide and diethylene glycol was prepared by mixing 200g of trioxane (2.2 mol) with 130 g trioxocane (1.1 mol) in dry methylene chloride. The solution became viscous over a period of several hours following the addition of a catalytic amount of trifluoromethane sulphonic acid.

The viscous solution was stabilizied with the addition of 1 ml of tributyl WO 90/13583 PCT/US89/01861 -17amine and was coated on 1750g of finely ground sodium fluoride. The resulting paste was dried in a vacuum oven at 60'C for 24 hours then weighed to determine the weight of the polymer (1750g sodium fluoride 173g of polymers). Fluorination of the powder using the conditions described in Example 2 yielded 270g of a medium viscosity fluid along with 94g of a tacky solid polymer. The chemical shifts observed in the 19 1 F NMR were essentially indistinguishable from the resonances observed for the fluid described in Example 2. However, the relative intensities were different because of the abundance of CF 2

CF

2

OCF

2 units being present in the polymer.

Example 6 25g of a copolymer of methylene oxide and epichlorohydrin which contained 4% epichlorohydrin was prepared by reacting trioxane with 4-chloromethyl-1,3-dioxolane in a 3:1 molar ratio. A white solid was formed which was ground to a fine powder and mixed with 150g of 200 mesh sodium fluoride powder. Fluorination of the polymer with fluorine diluted with 650 cc/min nitrogen for 48 hours at O'C followed by treatment with pure fluorine at 50'C gave 9.5g of a fluid and a small amount of an elastomeric solid (less than 1 gram).

WO 90/13583 PCT/US89/01861 -18- Industrial Applicability The perfluoropolyether fluids of this invention are useful as hydraulic fluids, heat transfer media or as bases for high performance greases which require fluids having a wide liquid range. The solid perfluoropolyethers can be used as elastomers and as fillers for high performance greases.

Equivalents Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.

Claims (11)

1. Perfluoropolyethers of the formula: Rf- (OCF 2 (OY)m-ORf 2 wherein: the units of OCF 2 and OY are randomly distributed along the polymer chain; Y is -CF 2 CF 2 -CFF 2 CF 2 -CF 2 CF 2 CF 2 CF 2 -CF (C 2 F 5 CF 2 -CF 2 CF20CFzCF 2 or -CF 2 CF(CFC1) wherein Rf and Rf 2 may be the same or different and are selected from -CF 3 -CzF s -C 3 F 7 -C 4 F 9 -C 2 F 4 Cl and -C 3 F 6 Cl, provided that R.f and Rf 2 are not both -CF 3 if Y is -CFCF 2 CF 2 -CF 2 CF 2 CF 2 CF 2 or -CF 2 (C 2 F) CF 2 n an integer greater than 1; m is an integer equal or greater than 1 such that the ratio n/m is greater than 1 and less than about 100; and the perfluoropolyethers having a molecular weight from abo-,c 300 to about 50,000 atomic mass units.

2. Perfluoropolyethers of Claim 1, wherein the ratio n/m is from about 100/1 to about 10/1.

3. A perfluoropolyether having a chain structure consisting essentially of repeating units -OCF 2 and -OY- randomly distributed along the chain and of having terminal groups selected from the group consisting of -CF 3 -CzF 5 -C 3 F7, -C 4 F 9 -C 2 FC1 and -C 3 FCl, provided that both end groups are not -CF 3 if Y is -CFCFCFC -CF 2 CF 2 CF 2 CF 2 or -CF,(C 2 F 5 )CF 2 wherein Y is -CF 2 CF 2 -CF 2 CF 2 CF 2 -CF 2 CF 2 CF 2 CF 2 -CF(C 2 F) CF 2 -CF 2 CF 2 OCF 2 CF 2 or -CF 2 CF(CF 2 the units being randomly distributed along the chain, the ratio of the number of -OCF 2 units to -OY- units being greater than 1 and less than about 100, the perfluoropolyether having a molecular weight of from about 300 to about 50,000 atomic mass units.

4. A method of preparing a perfluoropolyether having a chain structure consisting essentially of repeating units -OCF 2 and -OY- and of having perfluoroalkyl end groups selected from the group consisting of -CF 3 -C 2 F 5 -C 3 F 7 -C 4 F 9 -C 2 F 4 Cl and -C 3 F 6 Cl, wherein Y is -CF 2 CF 2 -CFCF 2 CF-, -CF(CF 3 )CF 2 -CF 2 CF 2 CF 2 CF 2 -CF(C 2 F) CF 2 -CF 2 CF 2 OCF 2 CF 2 or -CF 2 CF(CF 2 C) the repeating units being randomly distributed along the chain, provided that both end groups are not -CF 3 when Y is -CF 2 CF 2 CF 2 -CFICF 2 CF 2 CF 2 or -CF(C 2 Fs)CF 2 the ratio of the number of -OCF 2 units to -OY- units being greater than 1 but less than about 100, the perfluoropolyether having a molecular weight from about 300 to about 50,000 atomic mass units, comprising the steps of: a) providing a copolyether having a chain structure consisting essentially of methylene oxide units and at least one ethylene oxide propylene oxide, butylene oxide, diethylene oxide unit or epichlorohydrin for about every 100 methylene oxide units, the units being -21- randomly distributed along the polymeric chain; and b) perfluorinating the copolyether by exposing the copolymer to the elemental fluorine to produce a perfluoropolyether. A method of Claim 4, wherein the ratio of the number of -OCF 2 units to OY units ranges from 100/1 to 10/1.

6. A method of either Claim 4 or 5, wherein the perfluoropolyether is perfluorinated in the presence of NaF.

7. A method of preparing a perfluoropolyether containing difluoromethylene oxide and tetrafluoroethylene oxide repeating units randomly distributed along the polymeric chain and having terminal groups selected from the group consisting of -CF 3 -C 2 Fs, -C 3 F 7 -C 4 F 9 -C 2 F 4 C and -C 3 F 6 C1, the molar ratio of tetrafluoroethylene oxide units ranging from about 1 to about 10 percent, comprising the steps of: a) providing a copolyether comprising methylene oxide and ethylene oxide or diethylene oxide repeating units, the molar ratio of ethylene oxide units ranging from about 1 to about percent; and b) perfluorinating the copolyether by exposing the copolymer to the elemental fluorine to produce a perfluoropolyether. L -22-

8. A method of preparing a perfluoropolyether consisting essentially of -OCF 2 repeating units and having terminal groups selected from the group consisting of -CF 3 -C 2 Fs, -C 3 F 7 -C 4 Fg, -C 2 F 4 Cl and -C 3 FeCl comprising the steps of: a) providing a copolyether consisting essentially of methylene oxide units and ethylene oxide diethylene oxide units, the molar ratio of ethylene oxide or diethylene oxide units being about 1 to 2 percent; and b) perfluorinating the copolyether by exposing the copolymer to the elemental fluorine to produce a perfluoropolyether.

9. A method according to any one of Claims 4 to 8, wherein the perfluorination step is carried out by: i) exposing the copolymer to a mixture of an inert gas and fluorine gas, the fluorine concentration being from about 1 to about 25%; and ii) increasing the concentration of fluorine gas until the copolyether is exposed to pure fluorine gas thereby perfluorinating the copolyether to produce the perfluoropolyether. -23- A perfluorcpolyether according to Claim 1 substantially as herein described with reference to any one of the examples.

11. A method of preparing a perfluoropolyether according to Claim 4 substantially as herein described with reference to any one of the examples DATED: 5 January 1993 PHILLIPS ORMONDE FITZPATRICK Patent Attorneys For: EXFLUOR RESEARCH CORPORATION INTERNATIONAL SEARCH REPORT Initrnational Acolicalion No ?CT/US 89 /02.861 1. CLASSIFICATION OF SUBJECT MATTER (if seve'i ciassific3tior, symbois aooiy. -idicale srill According to International Patent Classification (IPC) of to boin National Classification and IPC IPC 5 C 08 G 2/30, C 08 G 65/30 11. FIELDS SEARCHED Minimum Documentation Searched Classification System Classification Symbol. 1Pc 5 C08 G Documentation Searched other thm j Minimum Documantation to the Extent that such Documents are Included In the Fields Searched 11t, DOCUMENTS CONSIDERED TO BE RELEVANT'# Category *I Citation of Document, 11 with Indication, where approarlate, of the relevant passage$ It Relevant to Claim No X :WO, A, 87/02993 (EXFLUOR RESEARCH) 2.-8 21 May 1987, see claims; examp..es Special categories of cited document.: 10 later document published aftar the International filing date ocuent efiingthe eneui aateat he at wich n nt ao priority date and not in conflict with the application but ""dcuntide in to e oaticl a e eeacte atwihio cited to understand the principle or theory underlying the consdere 10be o paticuar elevnceInvention earlier document but published on or after the international document of particular relevance: the claimed invention filing date cannot be considered novel or cannot be conaidered to document which may throw doubts on priority claimWs or Involve an Inventive step which is cited tO aetabia h the publication cts of another ""document of particular relevance;* the claimed invention citation or other special reason las specified) cannot be considered to involve en Inventive step when the document referring to an oral disclosure, use, exhibition or document is combined with one or more other such docu. other means monta, such combination being obvious to a person skilled document published prior to the International filing date but In the art. later than the priority date claimed ""document member of the same patent family IV, CERTIFICATION Date of the Actual Completion of the International Search Date of Mailing of this International Search Report December 1989 1?.7 01. 92 International Searching Authority Sintr of uli EUROPEAN PATENT OFFICE T.K. WiLiSn Form PCTIISA/2tO (second shoot) (Jansuary 1945) ANNEX TO THE 1INTERNATIONAL SEARCH REPORT ON INTERNATIONAL PATENT APPLICATION NO. US 8901861 SA 31448 This annex lists the patent family members relating to the patent documents cited in the above-mentioned international search report. The members are a, contained in the Luropean Patent Office EfDl1 file on 12101190 The European Patent Office is in no wa liable for these particulars AhiCh are merely given for the purpose of information. Patent document I Publication Patent family Publication cited in search repo"t date tnember(sl date WO-A- 8702993 21-05-87 AU-A- EP-A- ~JP-T- US-A- 6626786 0245446 63501367 4827042 02-06-87

19-11-87

26-05-88 02-05-89 For more details about this annex *see Official Journal of the European Patent Office, No. 12182