GB2148286A - Preparation of chlorotrifluoroethylene telomers with fluoroxytrifluromethane and bisfluoroxydifluoro methane - Google Patents

Abstract

Telomers of formula CF3O - (CFCl - CF2)n - X where n is 1-10 and X is F or OCF3, are formed by reacting chlorotrifluoroethylene with fluoroxytrifluoromethane or bisfluoroxydifluoromethane. The telomerization reaction is conducted either in liquid chlorotrifluoroethylene without a solvent or in solution. The telomers thus formed can optionally befluorinated (e.g. with ClF3) to improve their stability by replacing some or all of the chlorine by fluorine.

Description

SPECIFICATION Preparation of chlorotrifluoroethylene telomers with fluoroxytrifluoromethane and bisfluoroxydifluoro methane Background of the invention The present invention relates to novel telomers formed by the reaction of chlorotrifluoroethylene, hereinafter designated as "CTFE", with fluoroxytrifluoromethane, hereinafter designated as "FTM", or bisfluoroxydifluoromethane, hereinafter designated as "BDM". These telomers have properties which distinguish them from other CTEE telomers and make them commercially attractive products. Such properties include superior solvent characteristics which are useful in formulating non-flammable hydraulic fluids.

Various methods of preparing telomers from CTFE are known in the Prior art and have been practiced commercially for many years.

An article by William T. Miller, Jr. et al. in Industrial and Engineering chemistry, pages 333-337 (1947), entitled "Low Polymers of Chlorotrifluoroethylene", describes a process for producing low molecular weight polymers of CTFE by carrying out the polymerization in a solution of chloroform using benzoyl peroxides as polymerization promoters. Other solvents disclosed in the reference as being useful for this purpose include carbon tetrachloride and tetrachloroethylene. The solution is heated in a pressure vessel for 1-3/4 hours at 100"C., and the unreacted CTFE monomer and chloroform are removed by distillation, leaving a "crude" telomer of general formula CHCI2CF2CCIF)nCI, which can be further heated and distilled to yield products ranging from a light oil to a semi-solid wax or grease.In this formula, n is the chain length (the number of repeating units in the telomer chain), and is in the range of 1 to 20.

A more recent development in this field is described in a series of articles by Y. Pietrasanta et al. entitled "Telomerization by Redox Catalysis" appearing in the European Polymer Journal Vol. 12 (1976). This technology involves the reaction of a chlorinated telogen, such as carbon tetrachloride, with CTFE in the presence of benzoin and a suitable redox catalyst, such as ferric chloride hexahydrate (FeCI3-6H20). The telomerization reaction is suitably carried out in acetonitrile which is a common solvent for the reactants and catalysts.The telomerization reaction can be illustrated as follows, wherein n is as defined above:

FeCI3-6H20 CC14 + nCF2=CFCI ) CCl3(CF2CFCl)nCl (1) Benzoin The telomers produced according to the above-described process have end groups containing chlorine atoms. When used in a particular application, especially high temperature or corrosive applications, the chlorine atoms can be hydrolyzed, which may result in cleavage of the telomer and a loss of physical properties of the fluid. In order to prevent such a condition, the end groups are stabilized by fluorinating the telomer to replace chlorine atoms with fluorine. The fluorine atoms form a stronger bond with carbon and are less prone to cleavage. This results in a fluid which has superior performance over a wider range of operating conditions.

Fluorination of the telomer is accomplished by reaction with a suitable fluorinating agent, such as chlorine trifluorine or hydrogen fluoride. However, fluorination involves an additional process step which increases processing costs. It would be desirable to reduce the amount of fluorination required or eliminate this procedure in its entirety. It would also be desirable to develop superior telomers having improved physical characteristics, such as better solvent properties. These are the primary objectives of the present invention.

Summary of the invention The present invention relates to processes for preparing telomers by reacting chlorotrifluoroethylene with fluoroxytrifluoromethane or bisfluoroxydifluoromethane. The reaction can be conducted in liquid chlorotrifluoroethylene without a solvent at a temperature below the boiling point of chlorotrifluoroethylene (-30"C).

Alternatively, the reaction can be conducted in a suitable solvent at somewhat higher temperatures.

The present invention also relates to novel telomers which are characterized as having at least one trifluoromethoxy (-OCF3) end group.

The telomers produced by this process have improved physical properties as compared to telomers produced by reacting chlorotrifluoroethylene with carbon tetrachloride, or some equivalent telogen, as starting materials.

Description of the preferred embodiments The present invention is directed to both processes for producing telomers and novel telomers produced thereby.

According to the present invention, chlorotrifluoroethylene is reacted with fluoroxytrifluoromethane or bisfluoroxydifluoromethane in liquid CTFE or in solution. If the reaction is conducted in liquid CTFE, a temperature below the boiling point of CTFE, i.e. about -30 C, should be maintained. If high pressure conditions are used, the reaction temperature can be increased to about 1 00 C. An operable temperature range is therefore from about 100 C. to about -100"C. The absence of a solvent generally entails the use of lower temperatures than a solution telomerization process, but avoids the necessity of separation and purification of the product.

Alternatively, the reaction can be conducted in solution using a solvent, which is inert to fluorine under the reaction conditions. Suitable solvents are generally fluorinated and include, but are not limited to, fluorotrichloromethane, trifluoroacetic acid, trichlorofluoroethane, and the like. Of these solvents, fluoro trichloromethane is preferred. The solution temperature is preferably maintained in the range of from about -100"C. to about 100or. during the reaction.

The telomerization reaction can be carried out in a stirred reactor at the indicated temperature conditions.

The reaction of CTFE with FTM is illustrated below where n is typicaily from 1 to 10:

+ F3CO(CF2CFCl)nF II (2) + F(CF2CFCl)nOCF3 III + F3CO(CF2CFCl)nOCF3 IV As can be seen from reaction (2), the telomerization reaction generates a mixture of four discrete telomer species. Species I contains two -F end groups, while species II and Ill each contain one -OCF3 end group, and species IV contains two -OCF3 end groups. Species II, III and IV are novel telomers.

Although the monomer units of the telomers are depicted as being arranged in a particular order, they are actually randomly joined; that is, they can be joined in either head-to-head or head-to-tail fashion. Reference to a particular structural representation in the specification and claims is for convenience only, and should be construed accordingly.

The composition of the reaction product is believed to be at least partly dependent on solvent effects. For instance, the smaller percentage of species I in comparison to species II, lil and IV may be due to the preferential reaction of fluorine atoms with the solvent rather than with the CTFE as intended. The molecular weight distribution of the telomers has also been found to be non-uniform with the lighter weight products predominating.

The reaction of CTFE with BDM produces a more complex mixture of telomers.

The reaction of CTFE with FTM or BDM may produce telomers which contain some hydrolyzable chlorine.

In this event, it is necessary to fluorinate the telomers to replace the chlorine with fluorine. This results in a product having improved stability and non-reactivity. Chlorine trifluoride (CTFC3) is a suitable fluorinating agent for this purpose, although other fluorinating agents such as hydrogen fluoride can be used. The amount of such fluorination required, however, is less than for other CTFE telomers.

Both fluoroxytrifluoromethane and bisfluoroxydifluoromethane are known compounds. However, these compounds are not readily available in regular channels of commerce.

A convenient and inexpensive technique for producing FTM which has been reported in the literature is the reaction of carbon monoxide with excess fluorine. See, for example, G. H. Cady, Inorganic Synthesis, Vol.

8, pages 165-170 (1966). This reaction proceeds as follows:

A convenient and inexpensive technique for producing BDM which has been reported in the literature is the reaction of carbon dioxide with fluorine in the presence of a metal fluoride such as cesium fluoride. See, for example. F. A. Hohorst and J. M. Shreeve, Inorganic Synthesis, Vol. 11, pages 143-147 (1968), and Journal ofthe American Chemical Society, Vol. 89, pages 1809-10 (1967). This reaction proceeds as follows, wherein M designates a suitable metal such as cesium:

The telomers prepared according to this invention can be used in a variety of applications, such as fluids for hydraulic systems, pumps and instruments. In such applications, various additives may be used to modify the physical properties of the telomers.In addition to their inherent non-flammability and corrosion resistance, the telomers of this invention have been found to possess excellent solvent properites in comparison to other CTFE-derived fluids.

The following examples are intended to further illustrate the various embodiments and advantages of the present invention without limiting it thereby.

Example 1 Fluoroxytrifluoromethane was passed into a 3-neck flask containing chlorotrifluorethylene. The flask was equipped with a stirrer and a low temperature thermometer. The reaction temperature was maintained at -78 C. An aliquot of the material produced was reacted with chlorine trifluoride, and found to contain no hydrolyzable chlorine or fluorine in treatment with water, as determined by adding AgNO3 and CaCI2, respectively.

Example 2 Following the procedure of Example 1,0.57 gm/hr. offluoroxytrifluoromethane was added to a solution of 8.4 grams of chlorotrifluoroethylene in 50 ml. of a fluorotrichloroethylene solvent at 0 C. for 6.5 hours. The solution was degassed and the solvent evaporated yielding 7.21 grams of a liquid product. The product was analyzed using GC/MS and GC, and found to contain telomers having both -F and -OCF3 end groups.

Example 3- 12 The procedure of Example 2 was repeated using a variety of reaction conditions. The results are summarized in Table 1.

TABLE I Example No. CTFE (gms) Solvent (mix) FTMAddition Time of Wt of Rate Addition Temperature Product 3 7.1 CFC13(50) 0.57 gms./hr. 6.5 hr. -78"C. 3.5 gms 4 6.6 CFCI3(50) 1.17 gms./hr. 6.0 hr. -78"C. 5.4gms 5 6.7 CFC13(50) 0.57 gms./hr. 6.5 hr. -30 to -359C. 5.5 gms.

6 6.8 CFCl3(50) 1.71 gms./hr, 6.5 hr. -35"C. 2.8 gms.

7 8.4 CFC13(50) 0.57 gms./hr. 6.5 hr. 0 C 7.2 gms.

8 7.0 CFC13(50) 1.71 gms./hr. 6.5 hr. 0 C. 5.7 gms 9 6.7 CCI2FCCIF2(50) 0.57 gms./hr. 6.5 hr. -32 C 4.2 gms.

10 7.8 CF3CO2H(50) 0.58 gms./hr. 6.5 hr. 0 C 6.3 gms 11 105.5 CFC13(700) 5.83gms./hr. 7.3hr. -78C. 57.Ogms.

12 101.0 CFC13(700) 5.83 gms./hr. 8.0 hr. -78"C. 90.9 gms.

The products of Examples 3-12 were analyzed to determine the relative amounts of the individual telomer species (as shown in reaction 2) and the relative distribution of molecular weights (n value). The results are reported in Table II.

TABLE II Example No. Telomer Species { /0, n=2) n Valuelo/ol 1 ll & lI IV 2 3 4 3 7 43 50 52 40 7 4 3 31 66 69 29 2 5 8 47 44 22 49 29 6 13 44 43 31 44 25 7 5 41 54 37 48 15 8 16 47 36 32 41 27 9 15 47 38 32 42 26 10 5 46 59 32 44 24 11 4 35 62 59 36 5 12 9 46 45 47 43 10 Example 13 Five (5) grams of chlorotrifluoroethylene and 50 ml. offluorotrichloromethanewere placed in a 50 ml., three-neck, round bottom flask. The flask was equipped with a low temperature thermometer, a gas inlet tube, a gas outlet tube connected to an aqueous potassium iodine-acetic acid trap, and a magnetic stirring bar. The solution was cooled to -37 C. and BDM was added at a rate of 0.36 grams/hr. for two hours. The solvent was removed under reduced pressure yielding 0.5 grams of telomers as determined by GC analysis.

While various embodiments and exemplifications of this invention have been shown and described in the specification, modifications and variations thereof will be readily appreciated by those skilled in the art. It is to be understood, therefore, that the appended claims are intended to cover all such modifications and variations which are considered to be within the scope and spirit of the present invention.

Claims (11)

1. Atelomerhaving the formula CF30(CFCICF2)nX wherein n is from 1 to 10, and Xis F or OCF3.

2. Atelomer mixture comprising the components' a) F(CFCICF2)nF b) CF30(CFCICF2)nF c) F(CFCICF2)nOCF3 d) CF3(CFCICF2)nOCF3 wherein n is from 1 to 10.

3. A process for producing telomers which comprises reacting chlorotrifluoroethylene with fluoroxytrifluoromethane or bisfluoroxydifluoromethane.

4. A process according to claim 3 which is conducted in liquid chlorotrifluoroethylene without a solvent.

5. A process according to claim 4 which is conducted at a temperature of less than -30 C.

6. A process according to claim 3 which is conducted in a solvent.

7. A process according to claim 6 wherein the solvent is at least one fluorotrichloromethane, trifluoroacetic acid and trichlorotrifluoroethane.

8. A process according to any one of claims 3,4, 6 and 7 which is conducted at a temperature of from 1000coo -100"C.

9. A process according to any one of claims 3 to 8 wherein the resulting telomers are fluorinated by reaction with a fluorinating agent.

10. A process according to claim 9 wherein the fluorinating agent is chlorine trifluoride.

11. A process according to claim 3 substantially as described in any one of the Examples.