CA1272739A - Perfluorination of ethers - Google Patents
Perfluorination of ethersInfo
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- CA1272739A CA1272739A CA000522462A CA522462A CA1272739A CA 1272739 A CA1272739 A CA 1272739A CA 000522462 A CA000522462 A CA 000522462A CA 522462 A CA522462 A CA 522462A CA 1272739 A CA1272739 A CA 1272739A
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- ether
- hydrogen fluoride
- reactor
- scavenger
- polyether
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Abstract
ABSTRACT OF THE DISCLOSURE
The direct fluorination of ethers in the presence of hydrogen fluoride (HF) scavengers such as sodium fluoride and potassium fluoride is dis-closed. The (liquid or solid) are either mixed with the HF scavenger, coated onto the HF scavenger or placed separately with the HF scavenger into a fluorination reactor and fluorinated by exposure to gradually increasing concentrations of fluorine gas.
the HF scavenger permits use of more severe fluori-nation conditions i.e. higher initial fluorine, less gradual increases in fluorine gas concentrations and greater fluorine gas flow rates.
The direct fluorination of ethers in the presence of hydrogen fluoride (HF) scavengers such as sodium fluoride and potassium fluoride is dis-closed. The (liquid or solid) are either mixed with the HF scavenger, coated onto the HF scavenger or placed separately with the HF scavenger into a fluorination reactor and fluorinated by exposure to gradually increasing concentrations of fluorine gas.
the HF scavenger permits use of more severe fluori-nation conditions i.e. higher initial fluorine, less gradual increases in fluorine gas concentrations and greater fluorine gas flow rates.
Description
~Z17;2739 PERFLUORINATION OF ETHERS
Fiel_ of the Invention This invention is in the fields of polymer and fluorine chemistry.
05 Back~round Perfluoropolyethers have long been recognized for their outstanding thermal properties and wide liquid ranges. Perfluoropolyethers are normally made either from anionic polymeri~ation of per1uoro epoxide or from the W photolysis of tetrafluoro-ethylene or hexafluoropropylene in an inert solvent in the presence of oxygen. Both of these processes produce relatively expensive perfluoropolyethers.
The preparation of perfluoropolyethers by anionic polymerization of perfluoro epoxides ~irst involves the oxidation of a perfluoro olefin to a perfluoro epoxide, followed by anionic polymeriza tion of the epoxide to an acyl fluoride terminated perfluoropolyether and conversion of the acyl fluoride end groups to unreactive end groups by decarboxylation reactions or chain coupling photol-ytic decarboxylation reactions. The inability to form vcry high molecular weight polymers, the lack of stabiiity of many perfluoro epoxides, and the extreme difficulty encountered when attempting to 73~
polymerize substituted perfluoro epoxides have been cited as drawbacks to this method. In addition, anionic polymerization of perfluoro epoxides does not lend itself well to the manufacture of perfluoro 05 copolymers since perfluoro epoxides vary widely in reactivity.
An alternate synthetic method for the produc-tion of perfluoropolyethers involves the UV photo-lysis of tetrafluoroethylene and/or hexafluoropropy-lene in an inert solvent in the presence of oxygan.
This multistep process yields an acyl fluoride terminated polymer containing -CF20-, -CF2-cF2-cF~-cF2-~ -CF2-CF2-0-, and -CF(CF3)-CF2-o-repeating units as well as unstable peroxidic oxygen linkages (-CF~-0-0-CF2-). Treatment of the polymer at high temperatures and with fluorine gas gives a stable polymer containing perfluoroalkyl end groups.
~ee U.S. Patents 3,665,041; 3,8~7,978; 3,770,792;
and 3,715,378.
Although this process can produce copolymers, the process is completely random with little control over the kinds and number oE repeating units.
Undesirable linkages such as the peroxidic oxygen and the poly(difluoromethylet~e) portions of the polymer are unavoidable. These groups can give the polymer undesirable properties for many applica-tions. The formation of by-products and the need for fairly exotic solvents add significantly to the production costs of the polymer.
In contrast to the above-described process, direct ~luorination of hydrocarbon ethers allows one to i~elect amon~ many more structural ~orms of ethers becau5e synthetic methods ~or production of a wide variety of hydrocarbon ethers. The direct Eluori-i, , .
Fiel_ of the Invention This invention is in the fields of polymer and fluorine chemistry.
05 Back~round Perfluoropolyethers have long been recognized for their outstanding thermal properties and wide liquid ranges. Perfluoropolyethers are normally made either from anionic polymeri~ation of per1uoro epoxide or from the W photolysis of tetrafluoro-ethylene or hexafluoropropylene in an inert solvent in the presence of oxygen. Both of these processes produce relatively expensive perfluoropolyethers.
The preparation of perfluoropolyethers by anionic polymerization of perfluoro epoxides ~irst involves the oxidation of a perfluoro olefin to a perfluoro epoxide, followed by anionic polymeriza tion of the epoxide to an acyl fluoride terminated perfluoropolyether and conversion of the acyl fluoride end groups to unreactive end groups by decarboxylation reactions or chain coupling photol-ytic decarboxylation reactions. The inability to form vcry high molecular weight polymers, the lack of stabiiity of many perfluoro epoxides, and the extreme difficulty encountered when attempting to 73~
polymerize substituted perfluoro epoxides have been cited as drawbacks to this method. In addition, anionic polymerization of perfluoro epoxides does not lend itself well to the manufacture of perfluoro 05 copolymers since perfluoro epoxides vary widely in reactivity.
An alternate synthetic method for the produc-tion of perfluoropolyethers involves the UV photo-lysis of tetrafluoroethylene and/or hexafluoropropy-lene in an inert solvent in the presence of oxygan.
This multistep process yields an acyl fluoride terminated polymer containing -CF20-, -CF2-cF2-cF~-cF2-~ -CF2-CF2-0-, and -CF(CF3)-CF2-o-repeating units as well as unstable peroxidic oxygen linkages (-CF~-0-0-CF2-). Treatment of the polymer at high temperatures and with fluorine gas gives a stable polymer containing perfluoroalkyl end groups.
~ee U.S. Patents 3,665,041; 3,8~7,978; 3,770,792;
and 3,715,378.
Although this process can produce copolymers, the process is completely random with little control over the kinds and number oE repeating units.
Undesirable linkages such as the peroxidic oxygen and the poly(difluoromethylet~e) portions of the polymer are unavoidable. These groups can give the polymer undesirable properties for many applica-tions. The formation of by-products and the need for fairly exotic solvents add significantly to the production costs of the polymer.
In contrast to the above-described process, direct ~luorination of hydrocarbon ethers allows one to i~elect amon~ many more structural ~orms of ethers becau5e synthetic methods ~or production of a wide variety of hydrocarbon ethers. The direct Eluori-i, , .
2~39 nation of hydrocarbon ethers using the LaMar process offers an economical, versatile route to production of perfluoropolyethers.
Disclosure of the Invention This invention is-an improved method of directly fluorinating hydrocarbon ethers. The method comprises fluorinating the hydrocarbon ether by direct fluorination methods in the presence of a hydrogen fluoride scavenger such as sodium fluoride or potassium fluoride.
According to a broad aspect of the invention, there is provided a method of fluorinating a hydrocarbon ether, comprising contacting the hydrocarbon ether, in the presence of a hydrogen fluoride scavenger, with fluorine gas under conditions sufficient for fluorination of ether, the amount of hydrogen fluoride scavenger being sufficien-t to react with hydrogen fluoride formed during the fluorination and to prevent charring of the ether during the fluorination.
Fluorination in the presence of a hydrogen fluoride scavenger can be performed in several ways.
In the preferred mode, the scavenger (in powdered or pelle-t form) is mixed with the ether (oil or solid form). The blend is placed in a suitable fluorina-tion reac-tor and fluorinated by exposure to gradually increasing concentra-tions of fluorine gas. Alternat-ively, the ether may be coated onto the scavenger and fluorinated in this form. Though less efEective, the scavenger and the ether can be placed into the fluorination reactor separately (e.g. in separate containers).
For fluorination oE polyethers, the hydrogen fluoride scavenger and the polyether should be present in a ratio o~ about l:l to 20:1 (w/w~
scaverlcJer -to polyether.
3L~3~
- 3a -The preferred method of fluorination is the LaMar procedures o:E direct fluorina-tion (generally perfluorination). See Lagow, R.J. and Margrave, J.L.
Progress in Inorganic Chemistry, 26, 161 (1979). In the LaMar process, fluorine diluted with an inert gas is passed over the ether to be fluorinated initially at low concentrations (about 0.5 - 10~ fluorine) to minimize fragmentation of 05 the ether. As the fluorination reaction proceeds, the fluorine concentration and fIow rate of the gas are graaually increased until pure fluorine conditions are achieved and the ether is per-fluorinated.
The presence of a hydrogen fluoride scavenger allows the use of more severe fluorination con-ditions in this direct fluorination procedure, that is, higher fluorine concentrations and faster rates of fluorine delivery can be used in the presence of a hydrogen fluoride scavenger than can be used in the absence of a scavenger. For example, in the fluorination of polyethylene oxide initial fluorine levels of over 1~ and up to 2S%
and fluorine flow rates of over 8cc/min/gram of polymer can be used. In the absence of the scavenger~ severe charring of the ether can occur under these conditions.
In addition, the yield and quality of the perfluoropolye-ther product is improved when fluorination is conducted in the presence of a hydrogen flouride scavenger. The scavenger is believed to prevent the format-ion of ether-HF acid base complexes durins the fluorination reaction.
Sodium fluoride will react with hydrogen fluoride produced during fluorination to give sodium bi-fluoride (NaF ~ HF-~ NaHF2) thus eliminating HF
~2~
and preventing reaction of the HF wlth oxygen linkages of the ether.
The method of this invention can be used to fluorinate polyethers such as polyethylene oxide, 05 polypropylene oxide, and copolymers of ethylene oxide/methylene oxide of ethylene oxide/propylene oxide as well as simple ethers such as THF.
Best Mode of Carrying Out the Invention Sodium fluoride (NaF) is the preferred hydrogen fluoride scavenger for the fluorination procedure of this invention but others such as potassium fluoride can be used-. The NaF can be in the for~ of pellets or powder, and the hydrocarbon ether may be in a solid or a liquid form.
In the preferred mode of this invention, the hydrogen fluor:lde scavenger is mixed with the hydro-carbon ether to be fluorinated, and the mixture is fluorinated in a ~luorination apparatus by direct fluorination procedures to the desired level of fluorination In an alternate mode, the ether can be coated onto the hydrogen scavenger and fluorinated in this form. Solvents may be used to dissolve the ether and then coat it on. For example, NaF powder or pellets in the fluorination o liquid ethers, the use of NaF powder may be preferred because the powder has more surface a~ea than the pellets.
Consequently, coating the ether onto the powder increases the surface area of the liquid which is available for reaction with fluorine ~as. A liquid ether can be coated on the powder neat without use of a solvent.
~'27~2~3~
- If the ether is a solid, pellets of the hydro-gen fluoride scavenger are preferred because the solid perfluoroether product can be easily separated from the pellets using a coarse screen. However, 05 solids that do not powder well may be best handled by coating them on NaF powder to increase the surface area. Such solids can be dissolved, mixed with the NaF, and then dried to coat them on the NaF. Alternately, they may be coated neat if done above the melting point or in a mixer that will break up the solid ether.
Generally, the form of sodium fluoride or other scavenger to be used and treatment, if any, needed to coat the ether on the sodium fluoride may be ascertained by routine experiment with the par-ticular ether.
The fluorination of the ether in the presence of hydrogen fluoride scavengers can be performed in a variety of reactors. Stationary metal tubes, rotating drum reactors, fluidized beds, and solvent reactors are all conducive to the method. In a solvent reactor, the ether can be soluble in the solvent or the reaction may take place on a slurry or emulsion. In stationary tube reactors, the ether and the sodium fluoride powder or pellets should be mixed together fairly evenly. Placing the sodium ~luoride in one end of the reactor and the ether in the other end is not as effective as mixing the two together.
The amount of sodium fluoride added is ideally the stoichiometric amount needed to react with all of the hydrogen fluoride formed in the reaction.
Becaus~ sodium fluoride will react wi-th more than one equivalent of hydrogen ~luoride at temperatures ~27~3~
below 100C, somewhat less than a stoichiometric quantity can be used. Also, the perfluoro and partially fluorinated ethers do not complex hydrogen fluoride as strongly as hydrocarbon ethers so less 05 than a stoichiometric quantity may be used although best results are obtained with at least half of the stoichiometric amount of sodium fluoride. When using pellets, it may be best to use somewhat more than the stoichiometric quantity of HF as the crushing strength of the pellets is reduced if they absorb more than a stoichiometric quantity of HF.
In the perfluorination of polyethylene oxide, for example, some benefit is derived in the yield and quality of the perfluoroethers produced if as little as a 1:1 ratio is used. Optimal results are obtained for this polymer with a 4:1 by weight mixture of sodium fluoride to polyethylene oxide.
This is about the stoichiometric ratio. The use of more than a 4:1 by weight ratio does not improve the process. ~owever, if pellets of ~aF are used, a ratio of greater than 4:1 may be desirable because this prevents the pellets from absorbing more than a stoichiometric quantity of hydrogen fluoride. For liquid polyethers such as low molecular weigh~
polyethylene glycol, much more than a stoichiometric quant-ty may be desired so the fluorination can be done on a ~ree flowing powder rather than a paste.
Once the ether and sodium fluoride are placed in the reactor, fluorine gas diluted with helium, nitrogen or other inert gas is introduced in the reactor. With a hydrogen fluoride scavenger present initial fluorine concentration can range fro~ 0.5%
~7~73~
~luorine up to as high as 25~ fluorine. The highest dilution of fluorine and the lowest flow rate of fluorine are used at the beginning of the reaction as the ether is generally most reactive and most 05 susceptible to burning or ~ragmentation at this stage.
Oxygen can also be introduced into the system, if desired, to increase the amount of terminal acid groups on the perfluoroethers pro-duced.
As the fluorination proceeds, the fluorine concentration is raised and the fluorine flow rate may also be increased. If desired, the temperature can be raised before the reaction is complete to induce fragmentation or the ether may be heated to about 100lC in the presence of fluorine at the end o~ the reaction to eliminate terminal acid groups.
When the reaction is complete, the reactor is purged of excess fluorine and the products are removed. The product can be extracted with water to remove the sodium bifluoride/sodium fluoride or solvents can ~e used to extract the fluorinated ethers. If pellets of sodium ~luoride are used, the products can be separated using a coarse sieve.
The fluorination reaction can be done on a batch basis with times varying from a few hours to several days. Reactions can be performed in as little as six hJurs and as long a~ two weeks. The preferred time scale depends upon the reactor syste~
and there are virtually no limits to the theore-tically shortest time as long as the heat transfer is sufficient to prevent unacceptable amounts of polyme~ fra~mentat:ion.
72~73~
g Fluorination reactions can be done at tempera tures ranging from about -120C to about 200C.
Above about 350C addition of NaF will not complex hydrogen fluorideO At very low temperatures, NaF
05 would probably do very little good as the hydrogen fluoride would not have enough volatility to move out of the ether into the sodium fluoride. The preferred temperature range is from -40C to 1~0C.
Perfluoropolyethers, due to their good sta-bility and chemical inertness, are useful for many applications. For example, perfluoropolyether oils, such as perfluoropolymethylene oxide and perfluoro-polyethylene oxide are useful as high performance lubricants. Current synthetic methods for per-fluoroethers are expensive and consequently haveenjoyed limited use. Because the direct fluorina-tion process requires relatively inexpensive star-ting materials (hydrocarbon ethers and fluorine), it is an economical method of producing perfluoropoly-ethers that can be. The presence of a hydrogenfluorida scavenger during the fluorination of hydrocarbon ethers allows the use of very simple reactors ~o achieve results comparable to those ~chieved without a hydrogen ~luoride scavenger (i.e.
when extremely dilute fluorine is used and very long reaction times are used to minimize ether-HF complex formation). Hydrogen fluoride scavengers added to the hydrocarDon polyether allow the use of rela-tively harsh fluorination conditions yet provide good quality perfluoropolyethers and good yields.
The method of this invention improves the economy and efficiency of direct fluorination of hydrocarbon 273~
polyethers and allows the manufacture of inexpensive perfluoropolyethers. A wide range of ether struc-tures are available by this process because it is possible to produce a wide range of hydrocarbon 05 polyethers by well-established synthetic techniques.
The advantages gained by the addition of NaF to polyethers for fluorination are illustrated by the example given below. Three samples were placed in identical reactors and treated with the same fluori-nation conditions. The first sample contained onlylM MW polyethylene oxide, the second contained a 9:1 mixture of sodium bifluoride (NaHF~) and lM ~W
polyethylene oxide and the third contained a ~:1 mixture of NaF and lM MW polyethylene oxide. The lS second sample contained a lot of sodium bifluoride to show that the sodium fluoride does not simply act as an inert powder which prevents the small poly-ethylene oxide particles from sticking together and reducing the surface area available for reaction.
The results obtained with each sample are summarized in the table below.
SamDle ~1 _ Sample ~2 Sample ~3 2 grams lM Mh' Polyethylene 2 grams 1~ l Polyethylene 2 grams 1~ 1 Polyethylen~
oxide ground to pass 100 oxide ground to pass 100 oxide ground to pass 100 mesh. mesh mixed with 18 9 ~AHF2 mesh mixed with 8 9 ~aF
powder ground to pass 100 ground t~ pass 100 mesh.
mesh.
Dried in 100 cc/min N2 Dried in 100 cc/min N2 Dried in 100 cc/min N2 flow several hours. flow several hours. flow several hours.
Fluorination Program: Fluorinati4n Program: Fluorination PrDgram:
2 cc/min F2, 100 cc/ 2 cc/min F2, 100 cc/ 2 cc/min F2, 100 cc/
min N~ for 47 hours. min N for 47 hours. min N for 47 hours.
2 cc/min F2, 25 cc/ 2 cc/~in F , 25 cc/ 2 cc/2in F2, 25 cc/
min N2 for 4 hours. min N for24 hours. min N2 f~r 4 hours.
2 cc/min F2, 0 cc/ 2 cc/~in F2, 0 cc/ 2 cc/min F2, 0 cc/
min N2 for 13 hours. min N2 for 13 hours. min N for 13 hours.
Results: 0.7 9 weight Results: 1.1 9 weight Results:2 6.0 g weignt gain, sticky solid. gain, free-flo\Ying gain, free-flowing Solid~ extracted with po~er. Solids powder. Solids Freon~13 to give extracted with FreonTM extracted with FreonqM
0.82 9 oil, 1.9 9 113 to give 0.46 9 113 to give 0.50 9 insoluble solids. oil. Solids then oil. Solids then extracted with water extracted with \~ater to give 2 4 9 solids. t~ give 4.4 y solids Overall Y;eld: 2.7 9 Dverall Yield: 2.86 9 Overall Yield; 4.9 g (51~) (54~) (93~) In addition to the yield improvement, analysis of the oil in the F NMR reveals a more linear structure when sodium 1uoride is used as there are many fewer CF groups in the NMR. This results in an 05 oil that has a lower pour point with th~ same viscosity oil at room temperature. -The advantage ~ained by the addition o sodium 1uoride is even more dramatic when more s~vere .
~luc~rination conditions are used. Initial Eluorine i; ;:
, ~ , .
, . . .
Disclosure of the Invention This invention is-an improved method of directly fluorinating hydrocarbon ethers. The method comprises fluorinating the hydrocarbon ether by direct fluorination methods in the presence of a hydrogen fluoride scavenger such as sodium fluoride or potassium fluoride.
According to a broad aspect of the invention, there is provided a method of fluorinating a hydrocarbon ether, comprising contacting the hydrocarbon ether, in the presence of a hydrogen fluoride scavenger, with fluorine gas under conditions sufficient for fluorination of ether, the amount of hydrogen fluoride scavenger being sufficien-t to react with hydrogen fluoride formed during the fluorination and to prevent charring of the ether during the fluorination.
Fluorination in the presence of a hydrogen fluoride scavenger can be performed in several ways.
In the preferred mode, the scavenger (in powdered or pelle-t form) is mixed with the ether (oil or solid form). The blend is placed in a suitable fluorina-tion reac-tor and fluorinated by exposure to gradually increasing concentra-tions of fluorine gas. Alternat-ively, the ether may be coated onto the scavenger and fluorinated in this form. Though less efEective, the scavenger and the ether can be placed into the fluorination reactor separately (e.g. in separate containers).
For fluorination oE polyethers, the hydrogen fluoride scavenger and the polyether should be present in a ratio o~ about l:l to 20:1 (w/w~
scaverlcJer -to polyether.
3L~3~
- 3a -The preferred method of fluorination is the LaMar procedures o:E direct fluorina-tion (generally perfluorination). See Lagow, R.J. and Margrave, J.L.
Progress in Inorganic Chemistry, 26, 161 (1979). In the LaMar process, fluorine diluted with an inert gas is passed over the ether to be fluorinated initially at low concentrations (about 0.5 - 10~ fluorine) to minimize fragmentation of 05 the ether. As the fluorination reaction proceeds, the fluorine concentration and fIow rate of the gas are graaually increased until pure fluorine conditions are achieved and the ether is per-fluorinated.
The presence of a hydrogen fluoride scavenger allows the use of more severe fluorination con-ditions in this direct fluorination procedure, that is, higher fluorine concentrations and faster rates of fluorine delivery can be used in the presence of a hydrogen fluoride scavenger than can be used in the absence of a scavenger. For example, in the fluorination of polyethylene oxide initial fluorine levels of over 1~ and up to 2S%
and fluorine flow rates of over 8cc/min/gram of polymer can be used. In the absence of the scavenger~ severe charring of the ether can occur under these conditions.
In addition, the yield and quality of the perfluoropolye-ther product is improved when fluorination is conducted in the presence of a hydrogen flouride scavenger. The scavenger is believed to prevent the format-ion of ether-HF acid base complexes durins the fluorination reaction.
Sodium fluoride will react with hydrogen fluoride produced during fluorination to give sodium bi-fluoride (NaF ~ HF-~ NaHF2) thus eliminating HF
~2~
and preventing reaction of the HF wlth oxygen linkages of the ether.
The method of this invention can be used to fluorinate polyethers such as polyethylene oxide, 05 polypropylene oxide, and copolymers of ethylene oxide/methylene oxide of ethylene oxide/propylene oxide as well as simple ethers such as THF.
Best Mode of Carrying Out the Invention Sodium fluoride (NaF) is the preferred hydrogen fluoride scavenger for the fluorination procedure of this invention but others such as potassium fluoride can be used-. The NaF can be in the for~ of pellets or powder, and the hydrocarbon ether may be in a solid or a liquid form.
In the preferred mode of this invention, the hydrogen fluor:lde scavenger is mixed with the hydro-carbon ether to be fluorinated, and the mixture is fluorinated in a ~luorination apparatus by direct fluorination procedures to the desired level of fluorination In an alternate mode, the ether can be coated onto the hydrogen scavenger and fluorinated in this form. Solvents may be used to dissolve the ether and then coat it on. For example, NaF powder or pellets in the fluorination o liquid ethers, the use of NaF powder may be preferred because the powder has more surface a~ea than the pellets.
Consequently, coating the ether onto the powder increases the surface area of the liquid which is available for reaction with fluorine ~as. A liquid ether can be coated on the powder neat without use of a solvent.
~'27~2~3~
- If the ether is a solid, pellets of the hydro-gen fluoride scavenger are preferred because the solid perfluoroether product can be easily separated from the pellets using a coarse screen. However, 05 solids that do not powder well may be best handled by coating them on NaF powder to increase the surface area. Such solids can be dissolved, mixed with the NaF, and then dried to coat them on the NaF. Alternately, they may be coated neat if done above the melting point or in a mixer that will break up the solid ether.
Generally, the form of sodium fluoride or other scavenger to be used and treatment, if any, needed to coat the ether on the sodium fluoride may be ascertained by routine experiment with the par-ticular ether.
The fluorination of the ether in the presence of hydrogen fluoride scavengers can be performed in a variety of reactors. Stationary metal tubes, rotating drum reactors, fluidized beds, and solvent reactors are all conducive to the method. In a solvent reactor, the ether can be soluble in the solvent or the reaction may take place on a slurry or emulsion. In stationary tube reactors, the ether and the sodium fluoride powder or pellets should be mixed together fairly evenly. Placing the sodium ~luoride in one end of the reactor and the ether in the other end is not as effective as mixing the two together.
The amount of sodium fluoride added is ideally the stoichiometric amount needed to react with all of the hydrogen fluoride formed in the reaction.
Becaus~ sodium fluoride will react wi-th more than one equivalent of hydrogen ~luoride at temperatures ~27~3~
below 100C, somewhat less than a stoichiometric quantity can be used. Also, the perfluoro and partially fluorinated ethers do not complex hydrogen fluoride as strongly as hydrocarbon ethers so less 05 than a stoichiometric quantity may be used although best results are obtained with at least half of the stoichiometric amount of sodium fluoride. When using pellets, it may be best to use somewhat more than the stoichiometric quantity of HF as the crushing strength of the pellets is reduced if they absorb more than a stoichiometric quantity of HF.
In the perfluorination of polyethylene oxide, for example, some benefit is derived in the yield and quality of the perfluoroethers produced if as little as a 1:1 ratio is used. Optimal results are obtained for this polymer with a 4:1 by weight mixture of sodium fluoride to polyethylene oxide.
This is about the stoichiometric ratio. The use of more than a 4:1 by weight ratio does not improve the process. ~owever, if pellets of ~aF are used, a ratio of greater than 4:1 may be desirable because this prevents the pellets from absorbing more than a stoichiometric quantity of hydrogen fluoride. For liquid polyethers such as low molecular weigh~
polyethylene glycol, much more than a stoichiometric quant-ty may be desired so the fluorination can be done on a ~ree flowing powder rather than a paste.
Once the ether and sodium fluoride are placed in the reactor, fluorine gas diluted with helium, nitrogen or other inert gas is introduced in the reactor. With a hydrogen fluoride scavenger present initial fluorine concentration can range fro~ 0.5%
~7~73~
~luorine up to as high as 25~ fluorine. The highest dilution of fluorine and the lowest flow rate of fluorine are used at the beginning of the reaction as the ether is generally most reactive and most 05 susceptible to burning or ~ragmentation at this stage.
Oxygen can also be introduced into the system, if desired, to increase the amount of terminal acid groups on the perfluoroethers pro-duced.
As the fluorination proceeds, the fluorine concentration is raised and the fluorine flow rate may also be increased. If desired, the temperature can be raised before the reaction is complete to induce fragmentation or the ether may be heated to about 100lC in the presence of fluorine at the end o~ the reaction to eliminate terminal acid groups.
When the reaction is complete, the reactor is purged of excess fluorine and the products are removed. The product can be extracted with water to remove the sodium bifluoride/sodium fluoride or solvents can ~e used to extract the fluorinated ethers. If pellets of sodium ~luoride are used, the products can be separated using a coarse sieve.
The fluorination reaction can be done on a batch basis with times varying from a few hours to several days. Reactions can be performed in as little as six hJurs and as long a~ two weeks. The preferred time scale depends upon the reactor syste~
and there are virtually no limits to the theore-tically shortest time as long as the heat transfer is sufficient to prevent unacceptable amounts of polyme~ fra~mentat:ion.
72~73~
g Fluorination reactions can be done at tempera tures ranging from about -120C to about 200C.
Above about 350C addition of NaF will not complex hydrogen fluorideO At very low temperatures, NaF
05 would probably do very little good as the hydrogen fluoride would not have enough volatility to move out of the ether into the sodium fluoride. The preferred temperature range is from -40C to 1~0C.
Perfluoropolyethers, due to their good sta-bility and chemical inertness, are useful for many applications. For example, perfluoropolyether oils, such as perfluoropolymethylene oxide and perfluoro-polyethylene oxide are useful as high performance lubricants. Current synthetic methods for per-fluoroethers are expensive and consequently haveenjoyed limited use. Because the direct fluorina-tion process requires relatively inexpensive star-ting materials (hydrocarbon ethers and fluorine), it is an economical method of producing perfluoropoly-ethers that can be. The presence of a hydrogenfluorida scavenger during the fluorination of hydrocarbon ethers allows the use of very simple reactors ~o achieve results comparable to those ~chieved without a hydrogen ~luoride scavenger (i.e.
when extremely dilute fluorine is used and very long reaction times are used to minimize ether-HF complex formation). Hydrogen fluoride scavengers added to the hydrocarDon polyether allow the use of rela-tively harsh fluorination conditions yet provide good quality perfluoropolyethers and good yields.
The method of this invention improves the economy and efficiency of direct fluorination of hydrocarbon 273~
polyethers and allows the manufacture of inexpensive perfluoropolyethers. A wide range of ether struc-tures are available by this process because it is possible to produce a wide range of hydrocarbon 05 polyethers by well-established synthetic techniques.
The advantages gained by the addition of NaF to polyethers for fluorination are illustrated by the example given below. Three samples were placed in identical reactors and treated with the same fluori-nation conditions. The first sample contained onlylM MW polyethylene oxide, the second contained a 9:1 mixture of sodium bifluoride (NaHF~) and lM ~W
polyethylene oxide and the third contained a ~:1 mixture of NaF and lM MW polyethylene oxide. The lS second sample contained a lot of sodium bifluoride to show that the sodium fluoride does not simply act as an inert powder which prevents the small poly-ethylene oxide particles from sticking together and reducing the surface area available for reaction.
The results obtained with each sample are summarized in the table below.
SamDle ~1 _ Sample ~2 Sample ~3 2 grams lM Mh' Polyethylene 2 grams 1~ l Polyethylene 2 grams 1~ 1 Polyethylen~
oxide ground to pass 100 oxide ground to pass 100 oxide ground to pass 100 mesh. mesh mixed with 18 9 ~AHF2 mesh mixed with 8 9 ~aF
powder ground to pass 100 ground t~ pass 100 mesh.
mesh.
Dried in 100 cc/min N2 Dried in 100 cc/min N2 Dried in 100 cc/min N2 flow several hours. flow several hours. flow several hours.
Fluorination Program: Fluorinati4n Program: Fluorination PrDgram:
2 cc/min F2, 100 cc/ 2 cc/min F2, 100 cc/ 2 cc/min F2, 100 cc/
min N~ for 47 hours. min N for 47 hours. min N for 47 hours.
2 cc/min F2, 25 cc/ 2 cc/~in F , 25 cc/ 2 cc/2in F2, 25 cc/
min N2 for 4 hours. min N for24 hours. min N2 f~r 4 hours.
2 cc/min F2, 0 cc/ 2 cc/~in F2, 0 cc/ 2 cc/min F2, 0 cc/
min N2 for 13 hours. min N2 for 13 hours. min N for 13 hours.
Results: 0.7 9 weight Results: 1.1 9 weight Results:2 6.0 g weignt gain, sticky solid. gain, free-flo\Ying gain, free-flowing Solid~ extracted with po~er. Solids powder. Solids Freon~13 to give extracted with FreonTM extracted with FreonqM
0.82 9 oil, 1.9 9 113 to give 0.46 9 113 to give 0.50 9 insoluble solids. oil. Solids then oil. Solids then extracted with water extracted with \~ater to give 2 4 9 solids. t~ give 4.4 y solids Overall Y;eld: 2.7 9 Dverall Yield: 2.86 9 Overall Yield; 4.9 g (51~) (54~) (93~) In addition to the yield improvement, analysis of the oil in the F NMR reveals a more linear structure when sodium 1uoride is used as there are many fewer CF groups in the NMR. This results in an 05 oil that has a lower pour point with th~ same viscosity oil at room temperature. -The advantage ~ained by the addition o sodium 1uoride is even more dramatic when more s~vere .
~luc~rination conditions are used. Initial Eluorine i; ;:
, ~ , .
, . . .
3~
levels of over 153 and 1uorine addition rates ofover 8 cc/min per gram of polyethylene oxide starting material have been used to shorten the reaction time to about six hours. If the same reaction is tried ,05 without sodium fluoride, severe charring occurs.
With sodium fluoride, such severe reaction condi-tions still give about an eighty percent yield of perfluoropolyethylene oxide with a more linear structure than perfluoropolyethylene oxide prepared with much milder conditions when sodium fluoride is not used.
The invention is further illustrated by the following examples.
Example 1 480 grams of high molecular weight ~1 million) polyethylene oxide was mixed with 2400 grams sodium fluoride pellets and placed in a rotating drum reactor with a volume of about twenty liters. After purging for two hours at 3 liters per minute nitro-gen flow, the fluorine rlow is set at 480 cc/min and the nitrogen ~low is set at 3 liters per minute.
These conditions are maintained for a~out 36 hours at which time the nitrogen flow is reduced to l.S
liters per minute and the fluorine flow is main-tained at 480 cc/min. These conditions are main-tained for about 8 hours and then the nitrogen flow is cut o f and the reactor ~, exposed to pure fluorine at 480 cc/min for 4 hours or until a significant amount of 1uorine comes out of the reactor. The perfluoropolyethylene oxide is then g separated from the NaF/NaHF2 by sieving through a coarse screen. About 1030 grams of perfluoro-polyethylene oxide solids are obtained (81.4 yield).
05 Example 2 480g of high molecular weight (1 million) polyethylene oxide was mixed with 2,400g sodium powder (passed lO0 mesh sieve) and placed in a rotating drum reactor. After purging for two hours at 3 liters per minute nitrogen flow, the fluorine flow was set at 480 liters per minute. These condi-tions were maintained for about 36 hours at which time the nitrogen flow was reduced to 1.5 liters per minute and the fluorine flow was maintained at 480 cc/min. These conditions were maintained for about 8 hours and then the nitrogen flow was cut off and the reactor contents were exposed to pure fluorine (480 cc/min) for 4 additional hours ~or until a significant amount of fluorine comes out o~ the reactor). The perfluoropolyethylene oxide was separated from the NaF/NaHF2 by washing with approxi-mately 15 gallons of water. About lO50g of per-fluoropolyethylene oxide solids were obtained (83~.
~z~
Example 3 80g of lM molecular weight polyethylene oxide was mixed with 400g sodium fluoride pellets and placed in a rotating drum reactor. After purging 05 the reactor for 2 hours with 3 liters per minute nitrogen flow, the fluorine flow was set at 640 cc/min and *he nitrogen flow was set at 4 liters per minute. These conditions were maintained ~or about
levels of over 153 and 1uorine addition rates ofover 8 cc/min per gram of polyethylene oxide starting material have been used to shorten the reaction time to about six hours. If the same reaction is tried ,05 without sodium fluoride, severe charring occurs.
With sodium fluoride, such severe reaction condi-tions still give about an eighty percent yield of perfluoropolyethylene oxide with a more linear structure than perfluoropolyethylene oxide prepared with much milder conditions when sodium fluoride is not used.
The invention is further illustrated by the following examples.
Example 1 480 grams of high molecular weight ~1 million) polyethylene oxide was mixed with 2400 grams sodium fluoride pellets and placed in a rotating drum reactor with a volume of about twenty liters. After purging for two hours at 3 liters per minute nitro-gen flow, the fluorine rlow is set at 480 cc/min and the nitrogen ~low is set at 3 liters per minute.
These conditions are maintained for a~out 36 hours at which time the nitrogen flow is reduced to l.S
liters per minute and the fluorine flow is main-tained at 480 cc/min. These conditions are main-tained for about 8 hours and then the nitrogen flow is cut o f and the reactor ~, exposed to pure fluorine at 480 cc/min for 4 hours or until a significant amount of 1uorine comes out of the reactor. The perfluoropolyethylene oxide is then g separated from the NaF/NaHF2 by sieving through a coarse screen. About 1030 grams of perfluoro-polyethylene oxide solids are obtained (81.4 yield).
05 Example 2 480g of high molecular weight (1 million) polyethylene oxide was mixed with 2,400g sodium powder (passed lO0 mesh sieve) and placed in a rotating drum reactor. After purging for two hours at 3 liters per minute nitrogen flow, the fluorine flow was set at 480 liters per minute. These condi-tions were maintained for about 36 hours at which time the nitrogen flow was reduced to 1.5 liters per minute and the fluorine flow was maintained at 480 cc/min. These conditions were maintained for about 8 hours and then the nitrogen flow was cut off and the reactor contents were exposed to pure fluorine (480 cc/min) for 4 additional hours ~or until a significant amount of fluorine comes out o~ the reactor). The perfluoropolyethylene oxide was separated from the NaF/NaHF2 by washing with approxi-mately 15 gallons of water. About lO50g of per-fluoropolyethylene oxide solids were obtained (83~.
~z~
Example 3 80g of lM molecular weight polyethylene oxide was mixed with 400g sodium fluoride pellets and placed in a rotating drum reactor. After purging 05 the reactor for 2 hours with 3 liters per minute nitrogen flow, the fluorine flow was set at 640 cc/min and *he nitrogen flow was set at 4 liters per minute. These conditions were maintained ~or about
4 hours at which time the nitrogen flow was reduced to 2 liters per minute and the fluorine flow was maintained at 640 cc/min. These conditions are maintained for an additional 2 hours at which time the nitrogen flow was cut off and the reactor contents was exposed to pure fluorine (640 cc/min) lS for one adclitional hou~r (or until a significant amount of fluorine comes out of the reactor). The NaF/NaHF2 was separated from the product using a screen to give 158g of perfluoropolyethylene oxide (74.9% yield).
Example 4 78.6g of 4M molecular weight polyethylene oxide was dissolved in methylene chloride and mixed with 314.4 g of NaF powder (passes a 100 mesn screen).
The methylene chloride was evaporated leaving behind a solid which was ground to give a 50 mesh powder.
The powder was loaded in a rotating drum reactor which was purged ~or 2 hours with 3 liters per minute nitrogen prior to beginning the reaction~
Fluorine gas (80 cc/min) diluted with nitrogen ~4 liters per minute) was passed over the powder ~or approximately 36 hours (reactor temperature 30-~0C)~
7~
Next, the nitrogen flow was reduced to 1.5 liters per minute while the fluorine flow was maintained at 80 cc/min. These conditions were maintained for ~
hours and then the product was exposed to 80 ccjmin pure fluorine for several hours to ensure perfluori-nation. The NaF/NaHF2 was dissolved in water leaving behind 174g of a perfluoropolyethylene oxide solid (84.0% yield).
E~ample 5 320g of 600 MW polyethylene glycol was mixed with 1280g sodium f1uoride powder. The mixture was placed in a rotating drum reactor and fluorinated at 30-40'C using 320 cc/min fluorine and 16 liters per minute nitrogen (36 hours). The nitrogen was decreased to 1.5 liters/minute and the fluorination was allowed to continue for an additional 12 hours.
The polymer was treated with pure fluorine for several hours to ensure perfluorinat~on. A final fluorina-tion at llO C for 4 hours was used to con-vert reactive acetyl fluoride end groups Extrac-tion of the product with 2 liters Freon 113 gave 752g of perfluoropolyethylene oxide oil. An addi-tional 32g of FreonTM-insoluble perfluoropolyether solids were recovered by dissolving the NaF/NaHF2 coproduct in water (total yield of 92.9%).
Example 6 200g of polypropylene oxide (thick oil) was dissolved in 750 milliliters of methylene chloride and was mixed wi-th 1500g of sodium 1uoride powder.
After removal of the solvent the mixture was sieved 11%~;~7~3~
through a 50 mesh sieve to give a more uniform particle size. Fluorination of the mixture using 200 cc/min fluorine with decreasing amounts of nitrogen (similar to the programs used in the 05 previous examples) gave 160.4g of a FreonTM soluble oil (19F nmr was identical to that obtained for a KrytoxTM fluid (also a perfluoropolypropylene oxide) along with 240g of perfluoropolypropylene oxide solids (total yield of 69.9%).
1 Example 7 o A similar fluorination of a 70:30 ethylene oxide:propylene oxide copolymer (wax) was carried out. 480g of copolymer was dissolved in 2 li.ters of methylene chloride and was coated on 2400g of sodium fluoride powder. A gas flow of 300 cc/min fluorine and 3 liters per minute nitrogen was maintained for 36 hours. Th~ nitrogen was decreased to 1 L~min for an additional 12 hours. The polymer was treated with pure fluorine for several hours prior to treatment wi-th pure fluorine at llO C to remove the reactive end groups (6 hours). Extraction o~ the product with FreonTM 113 gave 495g oil. Removal of the NaF/NaHF2 gave an additional 356g of perfluoro-polyether solids (total yield 64.1%).
Exam~le 8 300g of polydioxolane powder was dissolved in 500ml of methylene chloride and mixed with 1200g NaF
powder. The solvent was evaporated and the resul-ting solid was ground cryogenically to give a powder ~L2~
which will pass a 50 mesh screen. The powder was placed in a 9" ID x 2' long aluminum drum reactor which rotates at 5 rev./min/ The reactor ~as flushed with nitrogen for several hours prior to 05 beginning the ~luorination. A gas flow of 300 cc/min fluorine and 2 L/min nitrogen was maintained for 36 hours. The nitrogen was decreased to 1 L/min for an addi-tional 12 hours. The polymer is treated with pure fluorine for several hours to insure perfluorination. A reactor temperature between O C
and +20 C was desirable for best results. A final fluorination ~t llO C for 4 hours was used to replace any residual hydrogen with fluorine and to convert reactive acetyl fluoride end groups to inert trifluoromethyl or pentafluoroethyl terminal groups.
Extraction of the powder with 2 liters of FreonTM
113 gave 370g of the desired difluoromethylene oxidetetrafluoroethylene oxide copolymer. An additional 160g of a FreonTM insoluble solid was also obtained which can be converted to a fluid via pyrolysis. Elemental analysis for solid:
calculated (C3F6O2)n: C, 19.80; F, 62.63, found:
C, 18.11; F, 62.53.
Example 9 Two grams of polydioxolane were placed in a nickel ~oat along with lOg of NaF pellets (1/8"
mesh). The boat was placed in a 1 1/2" nickel tube reac-tor and flushed with lOOcc/min N2 prior to beginning the fluorination. The fluorine and nitrogen flow rates were set at 2cc/min and 100ca/min, respectivel~. After 48 hours had ~27Z~3~
elapsed, the sample was treated for 12 hours with pure fluorine at lOO C. Extraction of the product mixture with FreonTM 113 gave 1.5g of a clear, low viscosity, nonvolatile oil. The NaF/NaHF2 pellets 05 were screened from the sample leaving behind 0.4g of a white solid (~otal yield: 38.6%). Infrared analysis and the NMR spectra of the oil were very similar to that observed for the oil prepared according to Example 1.
Example 10 Fluorination of polydioxolane using the very mild conditions as described in Examples 1 and 2 gives a perfluoro product with a minimal amount of chain degradation occurring during the fluorination reaction. The oil present in the sample results from the direct fluorination of lower molecular weight chains in the hydrocarbon starting material.
The oil to solid ratio of the final product can be increased by employing a two-step direct fluorina-tion process. In the initial phase, dilute fluorineis passed over the sample to replace the majority of the hydrogen. The second step, perfluorination of the sample with pure fluorine at elevated tempera-ture, give a product with a lower averaye molecular weight. The exothermicity of the reaction with elemental fluorine results in some chain ragmen-tation.
Two grams of polydioxolane was mixed with 10g of NaF powder. The reactor was purged with 100cc/m:ln N2 for 1 hour, ollowed by reaction oE the 2~3~
pol~er with 2cc/min F2 diluted with lOOcc/min N2 for 48 hours. Next, the polymer was subjected to pure fluorine at lO0C for 8 hours at which time some chain cleavage occurred. Using this procedure, oS 2.4g of oil and O.lg of solid material are obtained 15008~ total yield).
Industrial Applicability Because the direct fluorination process re-quires relatively inexpensive starting materials i.e. hydrocarbon polyethers and fluorine, this is a viable method of producing perfluoropolyethers. The addition of sodium flouride to the hydrocarbon polyethers in the fluorination allows one to use very simple reactors to commercially produce per-fluoropolyethers of good quality. It may be pos-sible to get as good results without a hydrogen fluoride scavenger if extremely dilute fluorine is used and very long reaction times are used to keep the ether-HF complex rom forming in the reactor to any great extent. However, hydrogen fluoride scavengers such as sodium fluoride or potassium fluoride added to the hydrocarbon polyether allow one to use relatively harsh fluorination conditions and still achieve good quality perfluoropolyethers and good product yield. The improvement of this invention provides for economic, large scale luo-rination of hydrocarbon polyethers and makes the manuEacture of inexpensive perfluoropolyethers possible. Polyethers of a wide range of structures can be fluorinated by this process because it is 73~
possible to produce a great variety of hydrocar~on polyethers.
Equivalents Those skilled in the art will recognize, or be 05 able to ascertain using no more than routine experi-mentation, many equivalents to the specific embodi-ments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.
Example 4 78.6g of 4M molecular weight polyethylene oxide was dissolved in methylene chloride and mixed with 314.4 g of NaF powder (passes a 100 mesn screen).
The methylene chloride was evaporated leaving behind a solid which was ground to give a 50 mesh powder.
The powder was loaded in a rotating drum reactor which was purged ~or 2 hours with 3 liters per minute nitrogen prior to beginning the reaction~
Fluorine gas (80 cc/min) diluted with nitrogen ~4 liters per minute) was passed over the powder ~or approximately 36 hours (reactor temperature 30-~0C)~
7~
Next, the nitrogen flow was reduced to 1.5 liters per minute while the fluorine flow was maintained at 80 cc/min. These conditions were maintained for ~
hours and then the product was exposed to 80 ccjmin pure fluorine for several hours to ensure perfluori-nation. The NaF/NaHF2 was dissolved in water leaving behind 174g of a perfluoropolyethylene oxide solid (84.0% yield).
E~ample 5 320g of 600 MW polyethylene glycol was mixed with 1280g sodium f1uoride powder. The mixture was placed in a rotating drum reactor and fluorinated at 30-40'C using 320 cc/min fluorine and 16 liters per minute nitrogen (36 hours). The nitrogen was decreased to 1.5 liters/minute and the fluorination was allowed to continue for an additional 12 hours.
The polymer was treated with pure fluorine for several hours to ensure perfluorinat~on. A final fluorina-tion at llO C for 4 hours was used to con-vert reactive acetyl fluoride end groups Extrac-tion of the product with 2 liters Freon 113 gave 752g of perfluoropolyethylene oxide oil. An addi-tional 32g of FreonTM-insoluble perfluoropolyether solids were recovered by dissolving the NaF/NaHF2 coproduct in water (total yield of 92.9%).
Example 6 200g of polypropylene oxide (thick oil) was dissolved in 750 milliliters of methylene chloride and was mixed wi-th 1500g of sodium 1uoride powder.
After removal of the solvent the mixture was sieved 11%~;~7~3~
through a 50 mesh sieve to give a more uniform particle size. Fluorination of the mixture using 200 cc/min fluorine with decreasing amounts of nitrogen (similar to the programs used in the 05 previous examples) gave 160.4g of a FreonTM soluble oil (19F nmr was identical to that obtained for a KrytoxTM fluid (also a perfluoropolypropylene oxide) along with 240g of perfluoropolypropylene oxide solids (total yield of 69.9%).
1 Example 7 o A similar fluorination of a 70:30 ethylene oxide:propylene oxide copolymer (wax) was carried out. 480g of copolymer was dissolved in 2 li.ters of methylene chloride and was coated on 2400g of sodium fluoride powder. A gas flow of 300 cc/min fluorine and 3 liters per minute nitrogen was maintained for 36 hours. Th~ nitrogen was decreased to 1 L~min for an additional 12 hours. The polymer was treated with pure fluorine for several hours prior to treatment wi-th pure fluorine at llO C to remove the reactive end groups (6 hours). Extraction o~ the product with FreonTM 113 gave 495g oil. Removal of the NaF/NaHF2 gave an additional 356g of perfluoro-polyether solids (total yield 64.1%).
Exam~le 8 300g of polydioxolane powder was dissolved in 500ml of methylene chloride and mixed with 1200g NaF
powder. The solvent was evaporated and the resul-ting solid was ground cryogenically to give a powder ~L2~
which will pass a 50 mesh screen. The powder was placed in a 9" ID x 2' long aluminum drum reactor which rotates at 5 rev./min/ The reactor ~as flushed with nitrogen for several hours prior to 05 beginning the ~luorination. A gas flow of 300 cc/min fluorine and 2 L/min nitrogen was maintained for 36 hours. The nitrogen was decreased to 1 L/min for an addi-tional 12 hours. The polymer is treated with pure fluorine for several hours to insure perfluorination. A reactor temperature between O C
and +20 C was desirable for best results. A final fluorination ~t llO C for 4 hours was used to replace any residual hydrogen with fluorine and to convert reactive acetyl fluoride end groups to inert trifluoromethyl or pentafluoroethyl terminal groups.
Extraction of the powder with 2 liters of FreonTM
113 gave 370g of the desired difluoromethylene oxidetetrafluoroethylene oxide copolymer. An additional 160g of a FreonTM insoluble solid was also obtained which can be converted to a fluid via pyrolysis. Elemental analysis for solid:
calculated (C3F6O2)n: C, 19.80; F, 62.63, found:
C, 18.11; F, 62.53.
Example 9 Two grams of polydioxolane were placed in a nickel ~oat along with lOg of NaF pellets (1/8"
mesh). The boat was placed in a 1 1/2" nickel tube reac-tor and flushed with lOOcc/min N2 prior to beginning the fluorination. The fluorine and nitrogen flow rates were set at 2cc/min and 100ca/min, respectivel~. After 48 hours had ~27Z~3~
elapsed, the sample was treated for 12 hours with pure fluorine at lOO C. Extraction of the product mixture with FreonTM 113 gave 1.5g of a clear, low viscosity, nonvolatile oil. The NaF/NaHF2 pellets 05 were screened from the sample leaving behind 0.4g of a white solid (~otal yield: 38.6%). Infrared analysis and the NMR spectra of the oil were very similar to that observed for the oil prepared according to Example 1.
Example 10 Fluorination of polydioxolane using the very mild conditions as described in Examples 1 and 2 gives a perfluoro product with a minimal amount of chain degradation occurring during the fluorination reaction. The oil present in the sample results from the direct fluorination of lower molecular weight chains in the hydrocarbon starting material.
The oil to solid ratio of the final product can be increased by employing a two-step direct fluorina-tion process. In the initial phase, dilute fluorineis passed over the sample to replace the majority of the hydrogen. The second step, perfluorination of the sample with pure fluorine at elevated tempera-ture, give a product with a lower averaye molecular weight. The exothermicity of the reaction with elemental fluorine results in some chain ragmen-tation.
Two grams of polydioxolane was mixed with 10g of NaF powder. The reactor was purged with 100cc/m:ln N2 for 1 hour, ollowed by reaction oE the 2~3~
pol~er with 2cc/min F2 diluted with lOOcc/min N2 for 48 hours. Next, the polymer was subjected to pure fluorine at lO0C for 8 hours at which time some chain cleavage occurred. Using this procedure, oS 2.4g of oil and O.lg of solid material are obtained 15008~ total yield).
Industrial Applicability Because the direct fluorination process re-quires relatively inexpensive starting materials i.e. hydrocarbon polyethers and fluorine, this is a viable method of producing perfluoropolyethers. The addition of sodium flouride to the hydrocarbon polyethers in the fluorination allows one to use very simple reactors to commercially produce per-fluoropolyethers of good quality. It may be pos-sible to get as good results without a hydrogen fluoride scavenger if extremely dilute fluorine is used and very long reaction times are used to keep the ether-HF complex rom forming in the reactor to any great extent. However, hydrogen fluoride scavengers such as sodium fluoride or potassium fluoride added to the hydrocarbon polyether allow one to use relatively harsh fluorination conditions and still achieve good quality perfluoropolyethers and good product yield. The improvement of this invention provides for economic, large scale luo-rination of hydrocarbon polyethers and makes the manuEacture of inexpensive perfluoropolyethers possible. Polyethers of a wide range of structures can be fluorinated by this process because it is 73~
possible to produce a great variety of hydrocar~on polyethers.
Equivalents Those skilled in the art will recognize, or be 05 able to ascertain using no more than routine experi-mentation, many equivalents to the specific embodi-ments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.
Claims (41)
1. A method of fluorinating a hydrocarbon ether, comprising the steps of:
a. placing the hydrocarbon ether and a hydrogen fluoride scavenger into a fluorine reactor, the amount of hydrogen fluoride scavenger in relation to the amount of ether being sufficient to react with the hydrogen fluoride formed during fluorination; and b. fluorinating the ether by:
i) establishing a flow of gas mixture of fluorine gas and an inert gas into the reactor under conditions which allow fluorination of the ether, the fluorine concentration of the gas mixture being about 0.5% to about 25%;
ii) gradually increasing the concentration of fluorine gas in the gas mixture to fluorinate the ether; and c. after the fluorination reaction is completed to desired degree, removing the fluorinated ether and the hydrogen fluoride scavenger from the reactor.
a. placing the hydrocarbon ether and a hydrogen fluoride scavenger into a fluorine reactor, the amount of hydrogen fluoride scavenger in relation to the amount of ether being sufficient to react with the hydrogen fluoride formed during fluorination; and b. fluorinating the ether by:
i) establishing a flow of gas mixture of fluorine gas and an inert gas into the reactor under conditions which allow fluorination of the ether, the fluorine concentration of the gas mixture being about 0.5% to about 25%;
ii) gradually increasing the concentration of fluorine gas in the gas mixture to fluorinate the ether; and c. after the fluorination reaction is completed to desired degree, removing the fluorinated ether and the hydrogen fluoride scavenger from the reactor.
2. A method of Claim 1, wherein the hydrocarbon ether is a polyether.
3. A method of Claim 1, wherein the hydrocarbon ether is mixed with the hydrogen fluoride scavenger.
4. A method of Claim 1, wherein the ether is coated onto the hydrogen fluoride scavenger.
5. A method of Claim 1, wherein the hydrogen fluoride scavenger is sodium fluoride or potassium fluoride.
6. A method of Claim 1, wherein the hydrogen fluoride scavenger and the ether are present in a weight ratio of about 1:1 to about 20:1.
7. A method of fluorinating a hydrocarbon ether, comprising the steps of:
a. mixing the hydrocarbon ether to be fluorinated and a hydrogen fluoride scavenger in powdered or pellet form, the amount of hydrogen fluoride scavenger in relation to the amount of ether being sufficient to react with the hydrogen fluoride formed during fluorination;
b. placing the mixture in a fluorine reactor;
c. fluorinating the ether by:
i) establishing a flow of gas mixture of fluorine gas and an inert gas into the reactor under conditions which allow fluorination of the ether, the fluorine concentration of the gas mixture being about 0.5% to about 25%; and ii) gradually increasing the concentration of fluorine gas in the gas mixture to fluorinate the ether; and d. after the fluorination is completed to desired degree, removing the fluorinated ether and the hydrogen fluoride scavenger from the reactor and separating the fluorinated ether from the hydrogen fluoride scavenger to obtain the fluorinated ether.
a. mixing the hydrocarbon ether to be fluorinated and a hydrogen fluoride scavenger in powdered or pellet form, the amount of hydrogen fluoride scavenger in relation to the amount of ether being sufficient to react with the hydrogen fluoride formed during fluorination;
b. placing the mixture in a fluorine reactor;
c. fluorinating the ether by:
i) establishing a flow of gas mixture of fluorine gas and an inert gas into the reactor under conditions which allow fluorination of the ether, the fluorine concentration of the gas mixture being about 0.5% to about 25%; and ii) gradually increasing the concentration of fluorine gas in the gas mixture to fluorinate the ether; and d. after the fluorination is completed to desired degree, removing the fluorinated ether and the hydrogen fluoride scavenger from the reactor and separating the fluorinated ether from the hydrogen fluoride scavenger to obtain the fluorinated ether.
8. A method of Claim 7, wherein the ether is a polyether.
9. A method of Claim 7, wherein hydrogen fluoride scavenger is sodium fluoride or potassium fluoride.
10. A method of Claim 7, wherein the hydrogen fluoride scavenger and the ether are mixed in a weight ratio of about 1:1 to about 20:1.
11. In a method of direct fluorination of a hydrocarbon ether, comprising fluorinating the hydrocarbon ether by contacting the ether with gradually increasing concentrations of fluorine gas, the improvement of fluorinating the ether in the presence of a hydrogen fluoride scavenger in powdered or pellet form, the hydrogen fluoride scavenger being present in an amount sufficient to react with essentially all of the hydrogen fluoride formed during the fluorination.
12. A method of Claim 11, wherein the hydrogen fluoride scavenger is sodium fluoride or potassium fluoride.
13. A method of Claim 11, wherein the hydrogen fluoride scavenger and the hydrocarbon ether are mixed together before contacting the ether with fluorine gas.
14. A method of perfluorinating a polyether, comprising the steps of:
a. introducing the polyether and a sodium fluoride into a fluorination reactor;
b. perfluorinating the polyether by:
i) establishing a flow of gas mixture of fluorine gas and inert gas into the reactor under conditions which allow fluorination of the ether, the fluorine gas concentration of the gas mixture being about 0.5% to about 25%; and ii) gradually increasing the concentration of fluorine gas in the gas mixture to perfluorinate the polyether thereby forming a perfluoropolyether;
and c. thereafter, removing the perfluoropoly-ether and the hydrogen scavenger from the reactor and, is necessary, separating the perfluoropolyether and the hydrogen fluoride scavenger.
a. introducing the polyether and a sodium fluoride into a fluorination reactor;
b. perfluorinating the polyether by:
i) establishing a flow of gas mixture of fluorine gas and inert gas into the reactor under conditions which allow fluorination of the ether, the fluorine gas concentration of the gas mixture being about 0.5% to about 25%; and ii) gradually increasing the concentration of fluorine gas in the gas mixture to perfluorinate the polyether thereby forming a perfluoropolyether;
and c. thereafter, removing the perfluoropoly-ether and the hydrogen scavenger from the reactor and, is necessary, separating the perfluoropolyether and the hydrogen fluoride scavenger.
15. A method of Claim 14, wherein the polyether is a solid or liquid polyether of a range of molecular weight from about 600 to about 4 million amu.
16. A method of Claim 14, wherein the polyether and sodium fluoride are mixed to form a blend for placement into the reactor.
17. A method of Claim 14, wherein the polyether is coated onto the sodium fluoride.
18. A method of Claim 14, wherein the ratio of sodium fluoride to polyether (w/w) is about 1:1 to 20:1.
19. A method of Claim 18, wherein the ratio (w/w) is 1:1 to 4:1.
20. A method of Claim 14, wherein the inert gas is helium or nitrogen.
21. A method of Claim 1, wherein the hydrocarbon ether is a linear polyether.
22. A method of Claim 1, wherein the hydrogen fluoride scavenger is present in the stoichiometric amount needed to react with substantially all of the hydrogen fluoride formed in the fluorination reaction.
23. A method of Claim 1, wherein the reactor is a stationary metal tube, a rotating drum reactor, a fluidized bed reactor or a solvent reactor.
24. A method of Claim 14, wherein the fluorine gas concentration of the gas mixture is about 15-25%.
25. A method of Claim 14, wherein the reactor is a stationary metal tube, a rotating drum reactor, a fluidized bed reactor or a solvent reactor.
26. In a method of direct perfluorination of a linear polyether, comprising perfluorinating the polyether by contacting the polyether with gradually increasing concentrations of fluorine gas, the improvement of perfluorinating the polyether in the presence of a hydrogen fluoride scavenger.
27. The improvement of Claim 26, wherein the hydrogen fluoride scavenger is sodium fluoride.
28. The improvement of Claim 27, wherein the sodium fluoride is in powder or pellet form.
29. The improvement of Claim 26, wherein the amount of hydrogen fluoride scavenger employed is sufficient to allow the polyether to be subject to an initial concentration of 15-25% fluorine gas without charring of the polyether.
30. The improvement of Claim 26, wherein the hydrogen fluoride scavenger is present in at least the stoichiometric amount needed to react with substantially all of the hydrogen fluoride formed in the fluorination reaction.
31. A method of Claim 26, wherein the reactor is a stationary metal tube, a rotating drum reactor, a fluidized bed reactor or a solvent reactor.
32. A method of fluorinating a hydrocarbon ether, comprising contacting the hydrocarbon ether, in the presence of a hydrogen fluoride scavenger, with fluorine gas under conditions sufficient for fluorination of ether, the amount of hydrogen fluoride scavenger being sufficient to react with hydrogen fluoride formed during the fluorination and to prevent charring of the ether during the fluorination.
33. A method of Claim 32, wherein the hydrocarbon ether is a polyether.
34. A method of Claim 33, wherein the polyether is a linear polyether.
35. A method of Claim 32, wherein the hydrogen fluoride scavenger is sodium flouride or potassium fluoride.
36. A method of Claim 32, wherein pure fluorine gas is used for the fluorination.
37. A method of Claim 32, wherein the ether is coated onto the hydrogen fluoride scavenger.
38. A method of Claim 32, wherein the hydrogen fluoride scavenger and the ether are present in a weight ratio of about 1:1 to about 20:1.
39. A method of Claim 32, wherein the hydrogen fluoride scavenger is in powder or pellet form.
40. A method of Claim 32, wherein the reactor is a stationary metal tube, a rotating drum reactor, a fluidized bed reactor or a solvent reactor.
41. A method of perfluorinating a polyether, comprising:
a. placing the polyether and a hydrogen fluoride scavenger in a fluorine reactor, the amount of hydrogen fluoride scavenger being sufficient to react with hydrogen fluoride formed during fluorina-tion; and b. fluorinating the polyether by introducing fluorine into the reactor under conditions sufficient for perfluorination.
a. placing the polyether and a hydrogen fluoride scavenger in a fluorine reactor, the amount of hydrogen fluoride scavenger being sufficient to react with hydrogen fluoride formed during fluorina-tion; and b. fluorinating the polyether by introducing fluorine into the reactor under conditions sufficient for perfluorination.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US79662385A | 1985-11-08 | 1985-11-08 | |
| US796,623 | 1985-11-08 |
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| Publication Number | Publication Date |
|---|---|
| CA1272739A true CA1272739A (en) | 1990-08-14 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000522462A Expired - Fee Related CA1272739A (en) | 1985-11-08 | 1986-11-07 | Perfluorination of ethers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1272739A (en) |
-
1986
- 1986-11-07 CA CA000522462A patent/CA1272739A/en not_active Expired - Fee Related
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |