JPH0725875B2 - Method for producing fluoropolyether - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for polymerizing fluoroalkylene oxide to obtain fluoropolyether having a high degree of polymerization.

[Problems to be Solved by Prior Art and Invention]

Fluoropolyether obtained by polymerizing fluoroalkylene oxide has excellent heat resistance and chemical resistance, and since it has better lubricity than mineral oil, it is used as a fluorine-based lubricating oil. Has been done. Since such a fluorine-based lubricating oil is used in a low-pressure atmosphere such as a vacuum pump, it is desired that it has a high boiling point, and it is preferably a fluoropolyether having a high degree of polymerization.

Therefore, a method for obtaining a fluoropolyether having a high degree of polymerization has been studied. For example, Journal of Fluorine Chemistry2
Volume 5 (1984), pages 241-253, describes that hexafluoropropylene oxide was polymerized with potassium fluoride as a catalyst. The composition of the obtained polymer was shown to be hexafluoropropylene oxide dimer 3%, trimer 10%, tetramer 27%, pentamer 30%, and hexamer 9%. Has been done. As described above, according to the above-mentioned method, at most, a polymer of about a hexamer was obtained, and a fluoropolyether having a higher degree of polymerization could not be obtained.

In addition, J. Macromolecular Science-Chemis
Try) A8 (1974), pp. 499-520, cesium alcoholate of hexafluoropropylene oxide trimer. It has been shown to polymerize hexafluoropropylene oxide by using as a catalyst, but this method also has a problem in that the steps are complicated and an expected high polymer cannot be obtained.

[Means for solving problems]

The present inventor has conducted extensive studies on the synthesis of fluoropolyethers having a high degree of polymerization, and as a result, by polymerizing fluoroalkylene oxide in the presence of a fluoroketone compound in addition to an anionic polymerization catalyst such as an alkali metal fluoride. Find that the above objectives are achieved,
The present invention has been completed.

That is, the present invention is a method for producing a fluoropolyether, which comprises polymerizing fluoroalkylene oxide in the presence of an anionic polymerization catalyst and a fluoroketone compound.

As the fluoroalkylene oxide used in the present invention, known compounds can be adopted without any limitation.
Generally, the fluoroalkylene oxide preferably used in the present invention is a compound having 2 to 5 carbon atoms. Specifically, perfluoroalkylene oxides such as tetrafluoroethylene oxide, hexafluoropropylene oxide, 2.2.3,3-tetrafluorooxetane and perfluoroisobutylene oxide are preferably used.

As the anionic polymerization catalyst used in the present invention, known catalysts used in general anionic polymerization can be used without any limitation. For example, alkali metal fluorides such as sodium fluoride, potassium fluoride, cesium fluoride, rubidium fluoride; tetraalkyl ammonium fluoride, tetraethylammonium fluoride, tetrapropylammonium fluoride, tetrabutylammonium fluoride, etc. Examples thereof include ammonium fluoride; alkali metal alkoxides such as sodium polyfluoroalkoxide, potassium polyfluoroalkoxide, and cesium polyfluoroalkoxide. Of these, the alkali metal alkoxide can be obtained by reacting a fluoroalkylcarbonyl fluoride with an alkali metal fluoride or tetraalkylammonium fluoride. Therefore, instead of using the above-mentioned alkali metal alkoxide, it is also possible to use a fluoroalkylcarbonyl fluoride and an alkali metal fluoride or tetraalkylammonium fluoride together. Specific examples of the above fluoroalkylcarbonyl fluoride include hexafluoropropylene oxide dimer, hexamer, perfluoropropylcarbonyl fluoride, perfluorobutyrylcarbonyl fluoride, ω-hydroperfluoroalkylcarbonylfluoride, ω-chloroperfluoroalkylcarbonyl fluoride, oxalyl fluoride, perfluoromalonyl fluoride, perfluorosuccinyl fluoride, perfluoroglutaryl fluoride, perfluoroadiponyl fluoride, hexafluoropropylene oxide to oxalyl fluoride 2 to 6 addition-polymerized compounds and the like can be mentioned.

The amount of the anionic polymerization catalyst described above can be used in a wide range, but when the rate of the polymerization reaction and the degree of polymerization are taken into consideration, 0.0001 to 1 mol of fluoroalkylene oxide is used.
It is in the range of 0.2 mol, preferably in the range of 0.001 to 0.1 mol.

Next, as the fluoroketone compound used in combination with the above-mentioned anionic polymerization catalyst, a known compound in which a part or all of hydrogen of a ketone compound having one or more carbonyl groups is substituted with fluorine is used without any limitation. Among these various fluoroketone compounds, in the present invention, when a compound having an infrared absorption spectrum of a carbonyl group present in the fluoroketone compound which has an absorption of 1785 cm ^-1 or less is used, particularly high polymerization is achieved. Preferred because it gives a fluoropolyether of a certain degree.

Such a fluoroketone compound preferably used in the present invention is represented by the following general formulas (I) and (II).

(However, R ₁ and R ₄ are the same or different alkyl groups or aryl groups, or a group in which some or all of the hydrogen atoms of these groups are substituted with fluorine atoms, R ₂ , R ₃ and R
₅ is the same or different fluoroalkylene group, X is an oxygen atom or a sulfur atom, and l and m are 0.
Or 1, and n is an integer of 1 or more. (However, when 1 and m are 0 at the same time, at least _one of R ₁ and R ₄ is a group in which some or all of the hydrogen atoms of an alkyl group or an aryl group are substituted with fluorine atoms.)] In the general formulas (I) and (II), the alkyl group represented by R ₁ and R ₄ is not particularly limited in carbon number,
It is preferably in the range of 1 to 10 from the viewpoint of easy availability.
Further, a phenyl group is the most easily available as the aryl group represented by R ₁ and R ₄ . The above general formulas (I) and (II)
In the above, the fluoroalkylene group represented by R ₂ , R ₃ and R ₅ is not particularly limited in carbon number, but for the same reason as above, it is preferably in the range of 2 to 5 carbon atoms. .

Specific examples of the fluoroketone compound that can be preferably used in the present invention are as follows. For example, Etc. can be mentioned.

In the present invention, the fluorokeone compound represented by the general formula (I) is preferable from the viewpoint of the degree of polymerization of the obtained fluoropolyether, and a compound in which l and m are 1 and X is an oxygen atom is preferable. .

The amount of the fluoroketone compound is not particularly limited, but in order to increase the polymerization degree of the fluoropolyether, the weight ratio to the fluoroalkylene oxide is 0.
It is preferable to select from the range of 1 to 20, more preferably 0.5 to 10.

The fluoroalkylene oxide polymerization reaction in the present invention is preferably carried out in an aprotic organic solvent. As the aprotic organic solvent, a known solvent used for the polymerization of fluoroalkylene oxide is used without any limitation.

For example, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, acetone, acetonitrile, propionitrile, adiponitrile, tetrahydrofuran, dioxane, benzonitrile, nitroethane,
Dimethyl sulfoxide, tetramethylene sulfone and the like can be used. These aprotic organic solvents are
Weight ratio of fluoroalkylene oxide to 0.05 ~
It is preferably used in the range of 2.

The polymerization reaction of the fluoroalkylene oxide is -50 ° C to 50 ° C, preferably -35 ° C to 10 ° C while stirring the reaction medium.
It is preferable to carry out the reaction while maintaining the reaction temperature of (1) and the pressure of the fluoroalkylene oxide in the range of 0.1 to 10 atm, preferably 0.5 to 3 atm.

Further, in order to reduce the viscosity of the high polymer of fluoroalkylene oxide formed in the reaction medium, a fluorine-based organic compound such as hexafluoropropylene, perfluorobutadiene, perfluorobutane, perfluorohexane, trichlorotrifluoroethane, etc. is added. It can also be used.

The highly polymerized fluoroalkylene oxide obtained by the method of the present invention is separated from the reaction medium by a usual operation and then fractionated by distillation. The high polymer of fluoroalkylene oxide thus obtained is obtained by contacting the acid fluoride group at the terminal with water to form a carboxylic acid group and then reacting with fluorine gas to substitute the carboxylic acid group with fluorine. Alternatively, it is also possible to synthesize an even higher molecular weight fluoropolyether by decomposing the acid fluoride group in the presence of ultraviolet rays and utilizing the coupling between carbon radicals generated at that time. Further, it is possible to synthesize a fluoroether compound in which the acid fluoride group is replaced with hydrogen by converting the acid fluoride group of the polymer of fluoroalkylene oxide into a carboxylic acid and then thermally decomposing it in ethylene glycol and sodium carbonate. . Various functional groups such as ester group by reaction of acid fluoride group with alcohol, acid amide group by reaction with amine, nitrile group by reaction with phosphorus pentoxide, vinyl ether group by thermal decomposition in the presence of potassium carbonate. It is possible to synthesize highly polymerized derivatives of fluoroalkylene oxides having groups.

〔effect〕

As can be understood from the above description, the degree of polymerization can be increased to 7 by conducting the polymerization of fluoroalkylene oxide in the presence of the anionic polymerization catalyst and the fluoroketone compound.
As described above, 9 or more fluoropolyethers can be obtained. Moreover, the method of the present invention, the polymerization reaction is extremely mild conditions, for example, temperature -50 ~ 50 ℃, pressure 0.1 ~ 1
It also has the feature that it can be performed under conditions such as 0 atm.

Therefore, the method of the present invention is a method of extremely easily obtaining a fluoropolyether having a high degree of polymerization, which has not been obtained by a conventional method, and has a large industrial value.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 40 parts by weight of 1,5 dimethoxyperfluoro-3-pontanone (carbonyl IR absorption spectrum 1775 cm ^-1 ), 10 parts by weight of tetraethylene glycol dimethyl ether, and 0.5 parts by weight of potassium fluoride were charged into a stainless steel autoclave, and the temperature was 0 ° C. 20 parts by weight of hexafluoropropylene oxide were introduced at a pressure of 1.5 atm over 8 hours while stirring at the temperature of. After the reaction, 1,5-dimethoxyperfluoro-
A layer composed of 3-pentanone and tetraethylene glycol dimethyl ether and a layer of fluoropolyether which is a polymer of hexafluoropropylene oxide were separated. The obtained fluoropolyether was 19 parts by weight. When this part by weight was analyzed by gas chromatography, there was almost no hexafluoropropylene oxide dimer or trimer. Therefore, this polymer is distilled, a portion of the fraction is taken to hydrolyze the acid fluoride group with an excess aqueous sodium hydroxide solution, and then by back titration of excess sodium hydroxide with sulfuric acid, The average degree of polymerization of the fluoropolyether was calculated. The results are shown in Table 1. When these fractions were analyzed by F-nuclear magnetic resonance spectrum and H-nuclear magnetic resonance spectrum, they were found to consist of fluoropolyether only.

Comparative Example 1 10 parts by weight of tetraethylene glycol dimethyl ether,
0.5 parts by weight of potassium fluoride was charged into a stainless steel autoclave, and 20 parts by weight of hexafluoropropylene oxide was introduced at a pressure of 1.5 atm for 8 hours while stirring at a temperature of 0 ° C. By the same operation as in Example 1, the average degree of polymerization of the obtained fluoropolyether was determined.
It was 2.9. Gas chromatograph analysis revealed that hexafluoropropylene oxide dimer was 32%, 3%.
The content was 57% for tetramer, 10% for tetramer, and 1% for pentamer. From this comparative example, it is clear that the presence of 1,5-dimethoxyperfluoro-3-pentanone makes it possible to obtain a highly polymerized product.

Example 2 60 parts by weight of 1.5-diethoxyperfluoro-3-pentanone (IR absorption spectrum of carbonyl: 1775 cm ^-1 ), 10 parts by weight of triethylene glycol dimethyl ether, and 1 part by weight of potassium fluoride were charged in a stainless steel autoclave, and -10 While stirring at a temperature of ° C, 40 parts by weight of hexafluoropropylene oxyside was introduced at a pressure of 1.5 atm over 8 hours. After the reaction, 38 parts by weight of fluoropolyether was obtained. The average degree of polymerization of this part by weight was measured by the same method as in Example 1 and found to be 10.2. As a result of gas chromatographic analysis, there was almost no 2 to 4 mer which was a low polymer of hexafluoropropylene oxide.

Example 3 60 parts by weight of 1,5-dimethoxyperfluoro-3-pentanone and 10 parts by weight of tetraethylene glucol dimethyl ether containing 1 mmol / g of cesium alkoxide which is a dimer of hexafluoropropylene oxide were charged in a stainless steel autoclave, 40 parts by weight of hexafluoropropylene oxide was reacted at a temperature of −10 ° C. under a pressure of 1.5 atm for 16 hours. After the reaction was completed, 37 parts by weight of fluoropolyether was recovered. The average degree of polymerization measured by the same method as in Example 1 was 12.4.

Comparative Example 2 Hexafluoropropylene oxide was reacted in the same manner as in Example 3 except that 1.5-dimethoxyperfluoro-3-pentanone was removed from the reaction medium of Example 3. After the reaction was completed, 40 parts by weight of hexafluoropropylene oxide was recovered. The average degree of polymerization measured by the same method as in Example 1 was 6.0.

Example 4 60 parts by weight of 1,5-dimethoxy-fluoro-3-pentanone, 10 parts by weight of tetraethylene glycol dimethyl ether, 0.5 part by weight of cesium fluoride and 5 parts by weight of malonyl fluoride were charged into a stainless steel autoclave,
Hexafluoropropylene oxide 10 at a temperature of 10 degrees
0 part by weight was introduced for 16 hours under a pressure of 1 to 3 atm and reacted. As a result, 7 parts by weight of hexafluoropropylene oxide dimer and tetramer and 96 parts by weight of dibasic acid obtained by addition-polymerizing hexafluoropropylene oxide from both terminals of malonyl fluoride were obtained. The average degree of polymerization of hexafluoropropylene oxide measured by the same method as in Example 1 was 15.1.

Example 5 20 parts by weight of 1,5-dimethoxy-perfluoro-3-pentanone, 1 part by weight of perfluorobutyryl fluoride, 0.5 part by weight of tetramethylammonium fluoride, and 5 parts by weight of diethylene glycol dimethyl ether were placed in a stainless steel autoclave. Charged, at a temperature of -74 ° C 2.
Charge 15 parts by weight of 2.3,3-tetrafluorooxetane,
The reaction was performed for 24 hours at a pressure of 3 atm or less while gradually increasing the temperature. After completion of the reaction, 13 parts by weight of an addition polymer of 2.2.3,3-tetrafluorooxetane was recovered. The average degree of polymerization of 2.2.3,3-tetrafluorooxetane measured by the same method as in Example 1 was 12.5.

Examples 6 to 8 30 parts by weight of various fluoroketones shown in Table 2, 10 parts by weight of tetraethylene glycol dimethyl ether and 1 part by weight of potassium fluoride were charged into a stainless steel autoclave, and tetrafluoro was added at a temperature of -15 ° C. 20 parts by weight of ethylene oxide was reacted for 48 hours under a pressure of 1 to 3 atm. As a result, about 18 parts by weight of fluoropolyether, which is a polymer of tetrafluoroethylene oxide, was obtained. The average degree of polymerization of each fluoropolyether measured by the same method as in Example 1 is shown in Table 2.

Claims (1)

[Claims] 1. A method for producing a fluoropolyether, which comprises polymerizing fluoroalkylene oxide in the presence of an anionic polymerization catalyst and a fluoroketone compound.