FR2622883A1 - PROCESS FOR THE PREPARATION OF A MIXTURE OF LOW MOLECULAR WEIGHT CHLOROTRIFLUOROETHYLENE TELOMERS - Google Patents

Abstract

The present invention relates to a process for preparing a mixture of low + brominated chlorotrifluoroethylene telomers. molecular acid, characterized in that chlorotrifluoroethylene reacts with CF3 CClBr2 in the presence of a catalyst composition comprising a reducible metal halide selected from FeCl3, FeBr3, Fe2 (SO4) 3, CuBr2, CuCl2, TiCl4, VCl3 and NiCl3 as well as a reducing agent capable of reducing the metal halide in the reaction mixture, chosen from iron, nickel, copper, titanium, vanadium and benzone, said reaction being carried out in a solvent common to the reactants and the catalyst. Application in non-flammable hydraulic fluids.

Description

The present invention relates to a process for the preparation of

  telomers of the formula: wherein n ranges from 1 to 10. The telomers of the present invention are low molecular weight saturated polymers which are useful in the preparation of the present invention.

  preparation of nonflammable hydraulic fluids.

  Various methods are known in the prior art for preparing chlorotrifluoroethylene telomeres ("CTFE") and are

  industrially for many years.

  In an article by William T. Miller, Jr. et al, published in "Industrial and Engineering Chemistry", pages 333-337 (1947), entitled "Low Polymers of Chlorotrifluoroethylene", there is described a process for the preparation of low CTFE polymers. molecular weight by polymerization in chloroform solution using benzoyl peroxide as a polymerization promoter. Other solvents described herein as being useful for this application include carbon tetrachloride as well as tetrachlorethylene. The solution is heated in a pressure vessel for 1 hour 3/4 at 100 ° C., and the unreacted CTFE monomer and chloroform are distilled off while retaining a crude telomer of the general formula CHCl 2 (CF 2 CClF) nCl. , which can then be heated and distilled to produce products in a form from a fluid oil to a wax or

semi-solid fat.

  Another process for the preparation of low molecular weight CTFE polymers has been described in US Pat. No. 2,788,375, issued April 9, 1957. This process comprises reacting CTFE with a saturated brominated compound in the presence of a source of radiation. Suitable brominated compounds include 1,2-dibromo-2-chlorotrifluoroethane (CF 2 BrCClFBr). The saturated bromopolychlorofluorinated compounds obtained by this process can then be distilled off, and the isolated fractions are reacted with chlorine to prepare polychlorofluorinated compounds. The compounds are predominantly high molecular weight telomers, i.e.

that n is greater than 4.

  Czechoslovak Patent No. 201708 published August 15, 1982, describes the reaction of CTFE with CBrClFCF2Sr using a radiation source at

  a temperature of 20 C to 30 C to prepare 1,4-

  dibromo-2,3-dichlorohexafluorobutane and 1,6-

  dibromo-2,3,5-trichlorononafluorohexane as the main

  the reaction products. These compounds correspond to the following formulas:

F 'F F

Br -C-C -C-C-Br (1)

F C 1 F

F F F F F F

Br-C CC-C-C-C Br (2)

, I

  The compounds (1) and (2) have in common the feature that they have the same end groups, i.e. --CF2Br as well as adjacent pairs of -CFC1 groups in the telomere structure. It is believed that telomeres having structures corresponding to those of compounds (1) and (2) are inherently more unstable and less easily separated from impurities than

  the telomeres of the present invention.

  A more recent development in this field is described in a series of articles by Y. Pietrasanta et al entitled "Telomerization by Redox Catalysis" published in "European Polymer Journal", Vol. 12 (1976). A technique is thus used in which carbon halogenated telogenic compounds, such as CCl 4 and CClBr, are reacted with CTFE in the presence of benzoin and a suitable redox catalyst, such as ferric chloride. The telomerization reaction is

  performed appropriately in acetonitrile

  trile which is a common solvent for the reagents and the catalyst. The telomerization reaction can be

illustrated as follows.

  FeCl3 CC13X + nCF2 = CFCl CCl3 (CF2CFCl) nX (3) Benzoin o X represents a chlorine or bromine atom. The reference further discloses that the use of CC13Br as a telogenic compound provides a lower degree of telomerization and a greater amount of monoaddition than would be obtained.

using CC14.

  The redox process has the advantage of directly preparing products of low molecular weight without the need to crack or split a polymer of a molecular weight

higher.

  A modification of the redox process is described in US Patent Application assigned to the same assignee as the present serial application number 816,183 filed January 6, 1986. According to this modification, telomers of structural formula Br-C- are prepared. C Br (4)

F} F. C B

  in which n varies from 1 to 10, by reacting

  chlorotrifluoroethylene with 1,2-dibromo-2-

  chlorotrifluoroethane (CBrClFCF2Br) in the presence of a redox catalyst composition. The redox catalyst composition comprises a reducible metal halide selected from FeCl 3, FeBr 3, CuBr 2, CuCl 2, TiCl 4, VCl 3 and NiCl 2 and a reducing agent selected from Fe, Ni, Cu, Ti, V and benzoin. This method has the advantage of being able to prepare CTFE telemers which can be easily separated into stable, low molecular weight, stable isomers and which can then be chlorinated to prepare

  nonflammable hydraulic fluids.

  Although the telomeres prepared according to the latter method represent an important advance over the prior art, it is still necessary to increase the yield of more desirable compounds of low molecular weight.

  using milder reaction conditions.

  The subject of the present invention is thus a process for preparing a telomeric mixture of structural formula: ## STR1 ## in which n varies from 1 to 10, characterized in that chlorotrifluoroethylene is reacted with 1,1-dibromo-1-chlorotrifluoroethane (CF 3 CClBr 2) in

  presence of an oxidation catalyst composition

  duction. The oxidation-reduction catalyst composition

  comprising a salt, generally a halogenide of a reducible metal selected from FeCl 3, FeBr 3, Fe 2 (SO 4) 3, CuBr 2, CuCl 2, TiCl 4, VCl 3 and NiCl 2, and a reducing agent capable of reducing the metal halide in the reaction mixture, selected from iron, nickel, copper, titanium, vanadium and benzoin, said reaction being carried out in a solvent common to

reagents and catalysts.

  Alternatively, the catalyst composition may comprise a metal halide in its reduced form without reducing agent. Suitable reduced metal halides include FeCl 2, FeBr 2,

FeSO4, CuBr and CuCl.

  As a common solvent for reactants and catalysts, acetonitrile is preferred, and the preferred catalyst composition comprises

ferric chloride and nickel.

  The telomerization reaction of the present invention proceeds at relatively low temperatures from about 70 ° C to about 150 ° C, and provides a relatively high yield of compounds.

of a low molecular weight.

  The telomerization process of the present invention employs the reaction of the

  chlorotrifluoroethylene with 1,1-dibromo-1-

  chlorotrifluoroethane in a solvent, such as acetonitrile, in the presence of a catalytic amount of a reducible metal halide and a suitable metal, or a reduced metal halide alone. This reaction can be illustrated by the

following way.

K

  CF3CC1Br2 + nCF2 = CFC1 - CF3CClBr (CF2CFC1) nBr (6)

o n varies from 1 to 10.

  In the reaction (6), K may represent a reduction of the oxidation-reduction catalyst having a salt, in general a reducible metal halide selected from FeCl 3, FeBr 3, Fe 2 (SO 4) 3, CuBr 2, CuCl 2, TiCl 4, VCl 3 and NiCl 3, as well as a reducing agent selected from iron, nickel, copper, titanium, vanadium and benzoin, the reducing agent to be capable of reducing the selected metal halide. Typical combinations of metal halides and reducing agents that may be used include FeCl 3 or FeBr 3 and Fe or Ni, TiCl 4 and Ti, CuCl 2 or CuBr 2 and Cu, NiCl 3 and Ni, VCl 3 and V, preferably FeCl3 and Ni. Mixtures and alloys of metal reducing agents are also capable of being used in the present invention. Alternatively, K may comprise a reduced metal halide without a reducing agent, the reduced metal halide including FeCl 2, FeBr 2, FeSO 4, CuBr and CuCl. The reaction (6) is carried out in a common solvent, such as acetonitrile, benzonitrile or propionitrile, preferably

acetonitrile.

  Reaction (6) makes it possible to prepare a mixture of individual telomeres having corresponding molecular weights at n values from 1 to 10, rather than pure isomers having a distinct structure, i.e. a single n-value. The separation of the individual telomeres from the mixture is effected by distillation by

  processes well known to those skilled in the art.

  Telomeres of lighter molecular weight, i.e., telomeres having a n-value of 4 or less, generally predominate in the reaction (6). Some of the lighter compounds, such as the telomere corresponding to a value of n of 1, have no known commercial value. However, this telomer can easily be returned or recycled in the telomerization reaction, and thus converted in this way into useful telomeres of higher molecular weight thereby increasing the overall yield of the reaction. Other telomeres are currently very interesting. Non-flammable hydraulic fluids require, for example, an average molecular weight corresponding to a value of n of 2 to 4. These fluids can be obtained by first preparing stabilized, ie chlorinated, individual telomeres having n from 2 to 4, and mixing these telomeres to obtain the required viscosity. Controlling the molecular weight distribution in reaction (6) is therefore essential since the most desirable products require a narrow molecular weight distribution. This can be achieved by maintaining the concentration in the reaction mixture, generally in metal halide (reducible or reduced) from about 0.01% to about 2% based on the weight of CTFE, and also by maintaining the reducing agent concentration in the mixture. at a rate of about 0.5% to about 10% based on the weight of the CTFE. By the method of the present invention, yields of 50% or more can be obtained in telomeres having a

value of n from 2 to 4.

  The preferred metal reducing agent is nickel as well as nickel alloys, such as Hastelloy C (Hastelloy is a registered trademark of Union Carbide Corporation). The metal may be physically present in the reaction mixture in various forms, such as powder, particles of various sizes, wires, plates, or in the form of a plating material on the inner surface of the reactor. The preferred form consists of a finely divided powder which is uniformly dispersed in the reactor by stirring

  mechanical, for example in a stirred reactor.

  The telomerization reaction is preferably carried out in a stirred reactor under conditions of high temperature and pressure, the temperatures generally being from about 70 ° C to about 150 ° C, and the pressures being generally about 520 KPa (75 ° C). psi) at about 3,200 KPa

(450 p.s.i).

  The products of the reaction (6) are distinguished by

  the distribution of the groups -CF2-, -CFC1- and -CBrCL-

  in the telomere chain, and by the presence of a

  terminal group -CF3 and a terminal group -CFClBr.

  These telomeres can be represented by the following formula. F Br F F F C C C C Br (5)! The telomers of formula (5) have a bromine atom on the terminal carbon atom and a bromine atom on the second carbon atom from the opposite end of the chain. These two bromine atoms are sufficiently reactive to participate in a reinitiation reaction, although the secondary bromine atom is slightly less reactive than the primary bromine atom. The reinitiation involving the secondary bromine atom often takes place when FeCl 3 is chosen as the reducible metal halide and a chain containing a trifluoromethyl branching group is obtained.

this is illustrated below.

  FeC13 CF3CClBr (CF2CFCl) nBr + CF2 = CFCl Br (CFClCF2) aCCl (CF2CFCl) bBr (7) CF3 the sum of a and b not being greater than 10. As a result, the products of reaction (6) can include both branched and straight chain isomers that may be present in the product

final according to various proportions.

-2622883

  The following nonlimiting examples are intended to further illustrate the various embodiments and advantages of the present invention. These examples illustrate the preparation of CTFE telomers using various compounds

  telogenes and telomerization processes.

EXAMPLE 1

  100 g of CF 3 CClBr 2, 60 g of acetonitrile, 1.5 g of FeCl 3 and 2.0 g of nickel powder were introduced into the glass jacket of a stirred 600 ml autoclave. After checking the pressure and purging with nitrogen, 120 g of CTFE was added. The autoclave was closed and heated slowly to C. The reaction was maintained at this temperature for 4 hours. The maximum pressure reached was 1,482KPa (215p.s.i). As the reaction progressed, an additional 47 grams of CTFE was added from a heated tank. The reactor was then cooled to room temperature and the CTFE

  not reacted was evacuated by ventilation.

  After opening the autoclave, 123 g of a reaction mixture were obtained which consisted of two liquid phases, this product was washed with

  dilute solution of HCl and then with water.

  Gas chromatographic analysis of the washed product indicated that about 60% of the CFCClBr 2 had reacted. The four carbon telomeric accounted for about 52% of the product and consisted of a single isomer. The six-carbon telomer consisted of two isomers, one straight-chain, the other branched. There was a larger amount of the branched isomer than the linear chain isomer. Some degree of bromine and chlorine addition has been observed on the telogenic compound. Both CF3CBr3 and CF3CC12Br were found in the product with a small amount of

  each of the telomeres derived from these products.

EXAMPLE 2

  100 g of CF3CClBr2, 60 g of acetonitrile, 3.0 g of FeC13 and 3.0 g of iron powder were introduced into the glass jacket of a stirred 600 ml autoclave. After controlling the pressure and purging with nitrogen, 111 g of CTFE was added. We closed

  the autoclave and heated slowly to 120 C.

  The reaction was maintained at this temperature for 4 hours. The maximum pressure reached was 1,379 KPa (200 p.s.i.g). During the course of the reaction, an additional 59 g of CTFE was added from a heated tank. The reactor was then cooled to room temperature and vented

unreacted CTFE.

  After opening the autoclave, 169 g of reaction mixture were obtained. The product was washed with dilute HCl solution and then with water, gas chromatographic analysis of the washed product revealed that about 70% of the CF3CClBr2 had reacted. The four-carbon telomeric accounted for about 42% of the product and consisted of a single isomer. A greater amount of back-fed telogen compounds in this product than in the

product of Example 1.

EXAMPLE 3

  A 600 ml stirred autoclave, 50 g of CF 3 CClBr 2, 30 g of acetonitrile and 2.0 g of FeCl 2 were introduced into the glass liner. After control of the pressure and purging with nitrogen, 112 g of CTFE was added. The autoclave was closed and heated slowly to 100 ° C. The reaction was held at this temperature for 4 hours. The maximum pressure reached was 1,517 KPa (220 p.s.i.g). During the course of the reaction, an additional 22 grams of CTFE was added from a heated tank. The reactor was then cooled to room temperature and evacuated

  CTFE not reacted by ventilation.

  After opening the autoclave, 75 g of reaction mixture were obtained. This product has been washed with

  dilute solution of HCl and then with water.

  Gas chromatographic analysis of the washed product revealed that about 57% of the CF3CClBr2 had reacted. The four-carbon telomeric accounted for about 36% of the product and consisted of a single isomer. The linear chain isomer accounted for most of the six carbon atom telomer. A smaller amount of back-up products than in both

  previous examples, was present.

EXAMPLE 4

  600 ml of stirred autoclave, 125 g of CF3CClBr2, 75 g of acetonitrile, 7.5 g of Fe2 (SO4) 3 and 5 g of benzoin were introduced into the glass liner. After control of the pressure and purging with nitrogen, 254 g of CTFE was added. We closed

  the autoclave and heated slowly to 115 ° C.

  The reaction was maintained at this temperature for 4 hours. The maximum pressure reached was 2482 kPa (360 p.s.i.g). The reactor was then cooled to room temperature, and the unreacted CTFE was vented. After opening the autoclave, 125 g of reaction mixture were obtained. This raw product was washed with

  dilute solution of HCl and then with water.

  Gas chromatographic analysis of the washed product revealed that about 54% of the CF3CClBr2 had reacted. The product had the following composition. Four-carbon telomer 39% Six-carbon telomer 26% Seven-carbon telomer 19% Ten-carbon telomer 6% Many modifications and variations can of course be made to the embodiments described above. without departing from the definition of the present invention mentioned in

the appended claims.

Claims (11)

  A process for preparing a low molecular weight brominated chlorotrifluoroethylene telomer mixture, characterized in that chlorotrifluoroethylene is reacted with CF3CClBr2 in the presence of a catalyst composition comprising a reducible metal halide selected from FeCl3, FeBr3 , Fe 2 (SO 4) 3, CuBr 2, CuCl 2, TiCl 4, VCl 3 and NiCl 3 and a reducing agent capable of reducing the metal halide in the reaction mixture, selected from iron, nickel, copper, titanium, vanadium and benzoin, said reaction being carried out in a solvent common to the reagents and catalyst.   2. Method according to claim 1, characterized in that the brominated low molecular weight chlorotrifluoroethylene telomers comprise linear chain telomers of formula CF3CClBr (CF2CFCl) nBr and branched isomers of formula Br (CFClCF2) aCClCF3 (CF2CFCl) bBr in which n, a and b vary from 1 to 10, the sum of a and b not being greater than 10.   3. Process according to claims 1 and 2 taken separately   characterized in that the number having a value ranging from 2 to 4 is present at least about % of the weight of the reaction product.   4. Process according to claims 3 taken separately   characterized in that the solvent comon is acetonitrile.   5. Process according to claim 4, characterized in that the catalyst composition comprises FeCl3 and nickel.   6. Process according to claim 5, characterized in that FeCl3 is present in the reaction mixture in an amount of approximately 0.01% to   about 2% by weight of chlorotrifluoroethylene.   7. Process according to the claims 1 to 6   It is characterized in that the reducing agent is present in the reaction mixture in an amount of from about 0.5% to about 10% by weight of chlorotrifluoroethylene. 8. Process according to claim 1, characterized in that the telomerization reaction is carried out at a temperature of approximately 70 ° C. and approximately 150 ° C. and at a pressure of approximately 520 KPa at approximately 3100 KPa.   9. Process for the preparation of a low molecular weight brominated chlorotrifluoroethylene telomer mixture, characterized in that chlorotrifluoroethylene is reacted with CF3CClBr2 in the presence of a catalyst comprising a reduced metal halide selected from FeCl 2, FeBr 2, Fe SO4, CuBr and CuCl, this reaction being carried out in a   solvent common to the reagents and the catalyst.   10. Process according to claim 9, characterized in that the common solvent is acetonitrile. 11. The method of claim 10,   characterized in that the catalyst is FeC12.