WO1992005135A1

WO1992005135A1 - Preparation of perfluoroalkyl-alkylene vinyl ethers

Info

Publication number: WO1992005135A1
Application number: PCT/US1991/004523
Authority: WO
Inventors: Lidia Teresa Calcaterra; Mathias Paul Koljack
Original assignee: AlliedSignal Inc
Current assignee: Honeywell International Inc
Priority date: 1990-09-18
Filing date: 1991-06-24
Publication date: 1992-04-02
Anticipated expiration: 1993-03-18

Abstract

A process for preparing perfluoroalkyl-alkylene vinyl ethers comprises the reaction of an alkyl vinyl ether with a perfluoroalkyl-alkylene alcohol, in particular an alcohol in which the alkylene group is ethylene. The reaction is carried out in the presence of a Pd2 complex catalyst, optionally in a solvent.

Description

PREPARATION OF PERFLUOROALKYL-ALKYLENE VINYL ETHERS

The invention is related in general to the preparation of fluorinated vinyl ethers, particularly vinyl ethers having 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 ates with polyfluoroethylene.

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_fC_nH_2n-O-CH=CH₂ where:

R_f is a perfluoroalkyl moiety

n is equal to or greater than 2

Such compounds may be termed perfluoroalkyl-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_fC_nH_2nOH + HC ≡CH

R_fC_nH_2n-O-CH=CH₂

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

R_fC_nH_2nOH + ClCH=CH₂ --->R_fC_nH_2n-O-CH=CH₂ 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. R_fC_nH_2nOH + CH₃COOCH=CH₂ R_fC_nH_2n-O-CH=CH₂+ CH₃COOH

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 R_fCH₂OH, that is, it would not be used for preparing perfluoroalkyl methylene vinyl ether, i.e., R_fCH₂-O- CH=CH₂ 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 when the alkylene moiety is a methylene group. Thus, the McKeon et al. method at first was not considered applicable to the preparation of perfluoroalkyl-alkylene vinyl ethers. However, to OUT surprise, the palladium acetate phenanthroline catalyzed transalkylation has been found to provide good yields of the desired perfluoroalkyl-alkylene ethers when the alkylene group C_nH_2n has two carbon atoms or more. This is particularly true when 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⁺² 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_fC_nH_2n-O-CH=CH₂

where

R_f 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_nH_2n group. preferably R_f has 4 to 10 carbon atoms and n is 2 to 4, most preferably R_f has 8 carbon atoms and n is 2.

The Pd⁺² complex used as a catalyst is preferably Pd(II) acetate phenanthroline. When used, a solvent must be capable of dissolving ootn reactants. The preferred solvent is selected from the group consisting of tetranydrofuran, dioxane, and dialkyl polyethers. Description of 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 R_fC_nH_2n-O-CH=CH₂ where:

R_f 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_nH_2n group

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

R - O - CH₂ = CH₂ 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_fC_nH_2n-OH 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. Alkyl Vinyl Ethers

Tne vinyl ethers used in the process of the invention have only hydrogen atoms attached to the carbon atoms of the vinyl group, that is, they 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 C₈H₁₇CH₂CH₂OH and C₆H₁₃CH₂CH₂OH.

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⁺² complex used by McKeon et al. has been found to be suitable in general for the present transvinylation reaction also. The Pd⁺² 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⁺² 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 Å to 50 Å.

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

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 phenanthrol ine 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⁺² 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-(1,10-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 mL 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-(1,10-phenanthroline) 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-(1,10- 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(CF₂)₄CH₂OCH₂=CH₂

This vinyl ether corresponds to a perfluoro butyl- methyl ene vinyl ether except for containing one hydrogen atom rather than being fully fluorinated. 5.0 g of the corresponding alcohol, H(CF₂)₄CH₂OH, (0.02155 moles) was combined with 42.6 mL of butyl vinyl ether (0.3232 moles) and 0.22 g (0.000538 moles) of diacetato-(1,10-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°C, 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/min 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, CH₃(CH₂)₂₀CH₂OH, obtained from Jarchem as Jarcol 1-24, was added to a 500 mL Erlenmeyer flask, along with 250 mL of butyl vinyl ether, 80 mL of tetrahydrofuran, and 1.0 g of Pd(II)diacetato-1,10-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 C₁₈-C₂₂ linear alcohols. 40 g of the Jarcol 1822C was added to a 1-L Erlenmeyer flask, along with 330 mL 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 C₈-C₂₂ 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 the 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 mg 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 H₂O and 0.3 mL of 96% H₂SO₄ 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 (C₈F₁₇CH₂CH₂OCH=CH₂). The contents were stirred and the flask was cooled with a dry ice/acetone mixture. Then 50 uL of BF₃ 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.

Claims

1. A process for preparing perfluoroalkyl-alkylene vinyl ethers comprising reacting an alkyl vinyl ether with a perfluoroalkyl-alkylene alcohol where the alkylene group has at least 2 carbon atoms at reaction conditions in the presence of Pd⁺² complex catalyst and optionally a solvent.

2. The process of Claim 1 where said perfluoroalkyl- alkylene vinyl ether has the formula R_fC_nH_2n-O-CH₂=CH₂ where

R_f 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_nH_2n group.

3. The process of Claim 1 wherein said perfluoroalkyl- alkylene alcohol is a perfluoroalkyl ethylene alcohol.

4. The process of Claim 1 wherein said alkyl vinyl ether is a secondary alkyl vinyl ether.

5. The process of Claim 1 where said Pd⁺² complex is palladium (II) acetate phenanthrol ine.

6. The process of Claim 5 wherein the Pd⁺² complex catalyst is present in an amount up to about 5 wt. percent.

7. The process of Claim 4 wherein R_f has 4 to 10 carbon atoms and n is 2 to 4.

8. The process of Claim 7 wherein R_f has 8 carbon atoms and n 1s 2.

9. The process of Claim 1 wherein said solvent is at least one member of the group consisting of tetrahydrofuran, dioxane, and dialkyl polyethers.

10. The process of Claim 1 wherein said alkyl vinyl ether has an alkyl group with 1 to 6 carbon atoms.

11. The process of Claim 10 wherein said alkyl group has 4 carbon atoms.

12. The process of Claim 1 wherein said reaction is carried out at a temperature of about 25° to 50°C.