The invention is related in general to the preparation of fluorinated vinyl ethers, particularly vinyl ethers dving no halogen or other substitution on the vinyl moiety.

Prior Art

Vinyl ethers containing fluorine atoms have many potential applications, including low surface energy coatings, resins, and elastomers. Many publications and patents are related to vinyl ethers in which the vinyl moiety contains fluorine atoms. For example, in Canadian Patent 860977 such vinyl ethers are prepared by the reaction of sodium alcohol tes with polyfl oroethylene.

The present invention is concerned with the preparation of fluorinateα vinyl ethers in which the vinyl moiety is not substituted. More particularly, tne vinyl ether may be represented by the formula

R _f C _n H _2n -0-CH=CH ₂

where:

Rf is a perfluoroal yl moiety n is equal to or greater than 2

Such compounds may be termed perfluoroal yl-alkylene vinyl ethers. Several potential methods of preparing such compounds would suggest themselves from the prior art, but none have been found to be as satisfactory as the present invention, as discussed in detail below.

Acetylation of an alcohol by the following reaction has been found to produce little vinyl ether and may lead to olefin formation.

R _f C _n H _2π 0H + HC ≡CH —> R _f C _n H _2n -0-CH=CH ₂

Another potential route is the reaction of vinyl chloride with fluorinated alkylene alcohol:

R _f C _n H _2n 0H + C1CH=CH ₂ >R _f C _n H _2n -0-CH=CH ₂

This method has been shown to be useful for making alkyl vinyl ethers but it is not considered suitable for preparing the present perfluoroalkyl-alkylene vinyl ethers because the corresponding alcohols are not believed to be sufficiently acidic to displace the chlorine atom from vinyl chloride. In addition, vinyl chloride is an undesirable reactant since it is a known carcinogen.

Another potential method is that shown in U.S. 2,732,370, which reacts fluorinated alcohols with vinyl acetate in the presence of mercuric acetate.

Rf,CnH,nOH + [H! ^g pSS?Q ^c -> CH,3C0OH

The patent is concerned with preparing perfluoroalkyl methyl vinyl ether. Since mercury catalysts pose serious waste management problems, their use is undesirable. Further, the reaction is carried out at below ambient temperatures, which is also undesirable. Also, vinyl ethers are unstable in the presence of acids.

Preparation of alkyl vinyl ethers from alkyl alcohols has been reported by McKeon et al., Tetrahedron, 28, 227-238 (1972). The method uses a palladium acetate phenanthroline catalyst to transfer a vinyl group from a vinyl ether to an alkyl alcohol. We have found that this method is not useful when the perfluoro compound is RfCH ₂ 0H, that is, it would not be used for preparing perfluoroalkyl methylene vinyl ether, i.e., RfCH ₂ -0- CH=CH ₂ since the corresponding alcohol does not react readily with an alkyl vinyl ether, as will be seen below. This contrasts with the mercury catalyzed reaction of U.S. 2,732,370 which can be used

wnen the alkylene moiety is a methylene grou; . Thus, the McKeon e al . method at first was not considered applicable to the preparation of perfluoroalkyl-alkylene vinyl ethers. However, to OUT surprise, the palladium acetate phenanthrol ine catalyzed tra-nsal ylation nas been found to provide good yields of the desired perfluoroalkyl-alkylene ethers when the alkylene group C _n H£ _n has two carbon atoms or more. This is particularly true wtsen the reaction is carried out according to the preferred embodiments to be described below.

Summary of the Invention

Perfluoroalkyl-alkylene vinyl ethers are prepared by reacting an alkyl vinyl ether with a perfluoroalkyl-alkylene alcohol at reaction conditions in the presence of w Pd complex catalyst and, optionally, with a solvent. In a preferred embodiment, the perfluoroalkyl-alkylene alcohol is one in which the alkylene group is ethylene and the alkyl vinyl ether is a secondary alkyl vinyl ether.

The perfluoroalkyl-alkylene vinyl ethers of the invention have the formula

^' R _f C _n H _2n -0-CH=CH ₂ frere

Rf is a perfluorinated alkyl group having 2 to 12 carbon atoms n is 2 to 6 and the oxygen atom is attached to a primary carbon of the C _n H _2n group.

preferably Rf has 4 to 10 carbon atoms and n is 2 to 4, most preferably Rf has 8 carbon atoms and n is 2. The Pd ⁺² complex used as a catalyst is preferably Pd(II) acetate phenanthroline.

riner. used, a solvent must be capable cf dissolving ootn reactants. The preferred solvent is selected from the group consisting cf tetranydrofuran, dioxane, and dialkyl polyethers.

5 Descr'pf ^' cn cf the Preferred Embodiments

The transvinylation reaction of McKeon et al. referred to earlier has been found to provide a desirable yield of perfluoro vinyl ether of the formula

10 ^R f ^C n ^H 2n-°- ^CH=CH 2

where:

Rf is a perfluorinated alkyl group having 2 to 12 carbon atoms , _c n is 2 to 6 and the oxygen atom is attached to a primary carbon of the C _n H _2n group

Preferably R has 4 to 10 carbon atoms and n is 2 to 4, most 20 preferably Rf has 8 carbon atoms and n is 2. The reaction thus involves a vinyl ether having the formula

R - 0 - CH ₂ = CH ₂

25 where R is an alkyl group, preferably having 1 to 6 carbon atoms, and most preferably is a secondary alkyl group, with a perfluoroalkyl-alkylene alcohol having the formula

R _f C _n H _2n -0H

30 where: n is 2 to 6, preferably 2 to 4, most preferably 2, when n is 2, these alcohols are referred to herein as perfluoroalkyl ethylene alcohols.

Al y-1 Vinyl Ethers

Tne vinyl etners used in the process of the invention have only hydroge ⁿ atoms attached to the carbon atoms of the vinyl group, that is, tney are not substituted vinyl groups. The vinyl etners may oe produced by the reaction of acetylene with the corresponding alcohol or by other methods familiar to those skilled in the art, such as dehydrohalogenation of bromo ethyl alkyl ethers. Secondary alkyl alcohols have been found to be much less reactive in transvinylation than linear alcohols, as will be seen below. Thus, if a vinyl ether of a secondary alcohol is used, the transvinylation reaction should be irreversible and provide a higher yield of the perfluoroalkyl-alkylene vinyl ether. The yield can be further improved by distilling the secondary alkyl alcohcl formed in the transvinylation reaction. Consequently, the use of secondary alkyl vinyl ethers, such as sec-butyl vinyl etner are particularly preferred.

While the alkyl group may contain 1 to 6 carbon atoms, 2 to 5 carbon atoms are preferred, and in particular 3 to 5 carbon atoms since sucn vinyl ethers have desirable boiling points. Thus, the alkyl vinyl ethers may be methyl, ethyl, propyl, butyl, pentyl, or hexyl vinyl ethers, and preferably the secondary alkyl groups such as isopropyl, sec-butyl, sec-pentyl, or sec-hexyl groups.

Perfluoroalkyl-Alkylene Alcohols

Generally, the fully fluorinated alkyl group will contain from 2 to 12 carbon atoms, preferably 4 to 10 carbon atoms, and most preferably 8 carbon atoms. The size of the alkyl group will be selected by the desired characteristics of the polymer which one wants to make from the fluorinated vinyl ether resulting from the process of the invention.

The alkylene group will be ethylene or have up to six carbon atoms as determined by the combined effect of the alkylene group and the perfluoroalkyl group on the reaction.

Sucn perfluoroalkyl-alkylene alcohols may be mace by telomerization reactions. Particularly, preferred alcohols are C ₈ H ₁₇ CH ₂ CH ₂ 0H and CgH ₁₃ CH ₂ CH ₂ 0H.

The Solvents When the perfluoroalkyl-alkylene alcohol is a solid, the transvinylation reaction of the invention may be carried out in the presence of a solvent for both the perfluoroalkyl-alkylene alcohol and the vinyl ether. Ethers are preferred.

Tetrahydrofuran has been found to be particularly useful, but others including dioxane and dialkyl polyethers may be used provided they are able to dissolve the selected fluorinated alcohols and vinyl ethers. Solvents also may be used when the reactants are liquid, if desired.

After the reaction has been completed, the solvent is normally removed by distillation. The perfluorinated vinyl ether may be separated from the starting materials by distillation or by chromatography.

The Catalyst The Pd complex used by McKeon et al. has been found to be suitable in general for the present transvinylation reaction

+? also. The Pd complex may be used as a homogeneous or heterogeneous catalyst. Palladium acetate alone supported on carbon or alumina possesses no catalytic activity in the process of the invention. As stated by McKeon et al. the palladium acetate phenanthroline complex may be supported on carbon for ease in handling. We have found that since the palladium acetate phenanthroline has a very low solubility in most solvents, a large amount of solvent is needed to impregnate the complex onto carbon. The carbon supported Pd complex thus is preferably prepared by first impregnating the complexing agent phenanthroline, which is readily soluble in benzene, on the carbon and then contacting the carbon with a solution of the Pd +? salt, such as palladium acetate. The resulting catalyst is separated by filtration.

The carbon may be the type used for decoloration of solutions in organic chemistry. Typically, it will have a mean pore radius of about 16 A to 50 A.

Alternatively, other supports may be used such as poly(styryl)bipyridine and poly(styryl) phenanthroline.

The amount of catalyst required will vary depending upon reaction conditions and the reactants, but generally up to about 5 wt. percent of palladium acetate phenanthroline complex, preferably about 2 to 5 wt. percent, will be employed to obtain the desired performance.

The Process

The alkyl vinyl ether and the perfluoroalkyl-alkylene alcohol can be mixed or dissolved in the selected solvent (if desired) in approximately equal molar proportions, although more generally, the amount of the vinyl ether may be up to about 15 to

20 times the stoichiometric amount required to react with the alcohol.

+? The Pd complex catalyst, which has previously been prepared as described above is added to the reactant solution and the mixture reacted at a temperature of about 25° to 50°C, preferably about 25° to 35°C for a period of time sufficient to complete the reaction. Typically, about 24 to 48 hours will be used. After the reaction is complete, the catalyst is removed. If a homogeneous reaction is used, charcoal is added to remove the catalyst. When a supported catalyst is used, the solids may be filtered out. The perfluoroalkyl-alkylene vinyl ether product is recovered by distilling the solvent, and then separating the product from the starting materials by distillation or chromatography.

Example 1 Preparation of Diacetato-d.lO-phenanthroline) Pd(II) Catalyst 6.7 g of Pd acetate was dissolved in 750 mL of benzene and then filtered. A solution of 5.38 g of 1,10-phenanthroline in

250 m!_ of benzene was added dropwise to the Pd acetate solution to form a yellow precipitate, which was filtered, washed with nexane, and dried. An 82 yield of crude diacetato-(l,10-phenanthrol ine) Pd(II) was obtained. Example 2

Preparation of Perfluorooctyl-ethyl Vinyl Ether 520 mL (5.0 moles) of butyl vinyl ether, 100 g (0.22 moles) of 1H, 1H, 2H, 2H-perfluorodecanol (perfluorooctyl ethylene alcohol), and 2 g (0.00495 moles) of diacetato-(l,10- phenanthroline) Pd(II) were combined in a 1-L Erlenmeyer flask covered with nitrogen, stoppered, and stirred at room temperature for 72 hours. Analysis of a sample of the mixture showed a yield of the perflorooctyl ethylene vinyl ether to be 75.2%.

Example 3

Comparative Preparation of H(CF ₂ )-CH ₂ OCH ₂ =CH ₂ This vinyl ether corresponds to a perfluoro butyl- methylene vinyl ether except for containing one hydrogen atom rather than being fully fluorinated. 5.0 g of the corresponding alcohol, H(CF ₂ ) ₄ CH ₂ 0H, (0.02155 moles) was combined with 42.6 L of butyl vinyl ether (0.3232 moles) and 0.22 g (0.000538 moles) of diacetato-(l.lθ-phenanthroline) Pd (II) in a 125-mL Erlenmeyer flask and stirred for 48 hours at room temperature. Analysis of the product by gas chromatography showed that less than 25% yield was obtained. This low yield may be compared with Example 2 in which a perfluorinated alcohol having an ethylene group adjacent the hydroxyl moiety gave a 75.2% yield.

Example 4

Comparative

Acetylation of a Perfluorinated Alcohol

25 g of a perfluorinated alcohol, 1-H, 1-H, 2H, 2H- perfluorodecanol, (0.0539 moles) was placed in a 100-mL, 3-neck, round-bottomed flask. The alcohol was melted at 40°C and then nitrogen was sparged into the liquid at 0.5 mL/min for 15

minutes. 1.0 g of KOH was added and the solution heated slowly to 80° , held for 1 hour, and then increased to 120°C. Frothing of the mixture delayed initiation of acetylene flow for 1-1/2 hours, but it was started at 0.5 mL/ in and continued for 7 hours. Nitrogen sparging then replaced the acetylene for 15 minutes, after which the solution was cooled. Analysis by infrared spectroscopy indicated that no vinyl ether had been formed.

Example 5 Comparative

Transvinylation of a Secondary Alcohol 40 g of sec-docosanol , CH ₃ (CH ₂ ) ₂ QCH ₂ OH, obtained from Jarchem as Jarcol 1-24, was added to a 500 mL Erlenmeyer flask, along with 250 L of butyl vinyl ether, 80 mL of tetrahydrofuran, and 1.0 g of Pd(II)diacetato-l,10-phenanthroline. The mixture was stirred at room temperature for 48 hours. Analysis by gas chromatography showed that only 2% of the sec-docosanol had been converted to the corresponding vinyl ether.

The above result may be compared with the reaction of a mixture of similar linear alcohols, Jarcol 1822C, which is a mixture of C _j _g-C linear alcohols. 40 g of the Jarcol 1822C was added to a 1-L Erlenmeyer flask, along with 330 L of butyl vinyl ether, 70 mL of tetrahydrofuran, and 1.0 g of Pd(II) diacetato- 1,10-phenanthroline. Again, the mixture was stirred at room temperature for 48 hours. Analysis by gas chromatography showed at 97% of the Cg-C ₂₂ alcohols had been converted to the corresponding vinyl ethers.

The results of the above experiments suggest that linear alcohols react much more readily than their secondary counterparts. Thus, if the initial vinyl ether is a secondary alkyl vinyl ether the by-product of transvinylation will be a secondary alcohol, which, because it does not back-vinylate, should effectively make the transvinylation more complete and thereby provide higher yields of the desired vinyl ethers.

The following examples illustrate uses of tr.e perfluoroalkyl ethyl vinyl ethers of the invention.

Example 6 Copolymerization of Perfluoroalkyl Ethyl Vinyl Ether with Maleic Anhydride

A textile coating was produced by reacting 0.4 g (0.00408 mol) of maleic anhydride with 2.0 g (0.00408 mol) of perfluorodecyl vinyl ether in the presence of 8.16 mL of 1,2 dichloroethane as a solvent, with 30 g of VAZO ^® 67 [2,2'- azobis(2-methyl butane nitrile) from Dupont] an initiator. The reactants were placed in a 15 mL pyrex tube, frozen with liquid nitrogen, evacuated and then thawed. The procedure was repeated two more times in order to ensure an oxygen-free atmosphere. Then, the tube was heated to 65°C and held for about 15 minutes, at which time polymerization appeared complete. The polymer was dissolved in hexane and analyzed by gas chromatography. Only 3% of the vinyl ether monomer remained and it was concluded that substantially all of the monomers had reacted.

Example 7

Terpolymerization of Perfluoroalkyl Ethyl Vinyl Ether With Maleic Anhydride and an Alkyl Vinyl Ether

Another textile coating was prepared by reacting 0.57 g (0.005831 mol) of maleic anhydride with 2.0 g (0.004082 mol) of perfluorodecyl vinyl ether and 0.517 g (0.001749 mol) of octadecyl vinyl ether. The reactants were combined in a 100 mL three-necked round bottomed flask. The octadecyl vinyl ether, 19.4 mL of 1,2- dichloroethane, and 44.8 mg of VAZO* 67 were placed in the flask and heated to 60°C, at which time the perfluorodecyl vinyl ether was added. After 80 minutes, heating ceased and air admitted to stop polymerization. 20 mL THF was added and the polymer precipitated in cold water. About 900 mg of the recovered polymer was dissolved in THF and then hydrolyzed by adding 1.5 mL H ₂ 0 and

0.3 mL of 96% H ₂ S0 ₄ and refluxing for 6 hours. After precipitating in water about 620 mg of polymer was recovered, which could be redissolved and used as a textile coating.

Example 8 Homopolymers of Perfluoro Alkyl Ethyl Vinyl Ethers

To a three-necked flask provided with a magnetic stirrer, a condenser, and a nitrogen atmosphere, was added 3g of perfluorooctyl ethylene vinyl ether (CgF ₁₇ CH ₂ CH ₂ 0CH=CH ₂ ). The contents were stirred and the flask was cooled with a dry ice/acetone mixture. Then 50 uL of BF ₃ etherate was added to the flask and the dry ice/acetone removed to allow the flask to warm to room temperature. The liquid thickened and a plastic solid appeared. Analysis of the polymer indicated that all of the vinyl ether groups had reacted.