NEW PERFLUOROALKANES OBTAINED BY PHOTOCHEMICAL FLUORINATION AND USE THEREOF AS POLYMERIZATION INITIATORS

Abstract: The present invention relates to branched perfluoroalkanes which, having bonds between a quaternary carbon atom and a tertiary carbon atom, easily undergo a homolytic scission of the C-C bond thereby releasing (non-persistent) radicals which may be used as initiators of polymerization of ethylenically unsaturated monomers. A further object of the present invention are new perfluoroalkanes having at least 9 carbon atoms belonging to the above described group.

Description: NEW PERFLUOROALKANES OBTAINED BY PHOTOCHEMICAL FLUORINATION AND USE THEREOF AS POLYMERIZATION INITIATORS The present invention relates to new radical ini¬ tiators of polymerization of ethylenically unsaturated monomers . Recently increasing attention has focused on the search of new polymerization initiators, in particular of fluorinated olefins. Among such initiators the per- fluoroalkyl radicals proved to be particularly interesting. At present, however, the generators of perf1 uoroal yl radicals are often too stable, such as, for instance CF I and azomethane hexaf1 uoride, which need too high working temperatures in polymerization. See for instance: Rossi and Golden Int. J. Che . Kinetics 1979, page 775, Okafo and Whittle, Int. Journal of Chem. Kinetics, page 287 (1975) and W.A. Sheppard CM. Sharts "-Organic fluorine Chemistry" page 89 (1969) . It is also common knowledge that use may be made of perfl uoroacyl peroxides , which present some advantages in comparison with the above mentioned initiators; they are, however, expensive and cannot be prepared easily, moreover they may be hydrolyzed with ease. Their application on industrial scale proves to be limited. Therefore in industrial processes use is made of non-f1 uori nated initiators, such as persulfates in the dispersion polymerization of fluorinated monomers, for instance of C-F. or In that case > reactive terminals are introduced, which decrease polymer character¬ istics, and therefore expensive treatments of the polymer are required, in order to convert the terminal groups into non-reactive groups ' (D.I. Mc. Cane Encyclopedia of Polymer Science and Technology vol. 13 pages 523-670). In European Patent 121.898 a perfl uoroal yl radical was synthetized and isolated, which was stable at room temperature and was proposed as a polymerization initiator. This product, however, is obtained with low yields and because the product is a perfluoroalkyl radical, it requires some precautions as regards storage and treatment, in order to avoid its decomposition. Moreover the radical obtained according to this process, cannot easily be separated from the reaction raw product. This separation is generally necessary, owing to the presence of perfl uorool efi nes together with the perfluoro- alkyl radical, as these perfl uorool efi ns may interfere with the polymerization monomers. The object of the present invention is a process for the polymerization of ethylenically unsaturated monomers comprising as polymerization initiator a branched per- fluoroalkane or a mixture of branched perfluoroal anes having adjacent two quaternary carbon atoms or a quaternary carbon atom and a tertiary carbon atom, said perfiuoroalkane having at least 9 carbon atoms. Such perfluoroal anes, being stable at room tempera¬ ture, having practical and unlimited storage properties, do n require the precautions that were necessary for the polymeriz tion initiators of the prior art, but can be introduced as su into the reaction medium and only at the polymerization temperature are they able to generate radicals. Known per¬ fluoroalkanes belonging to this class are for example the fol 1 owi ng : This product is prepared according to US-A-3962358. CF. F 2- CF 3 F - C — C — CF. (II) CF, CF„ - CF. CF. (US-A-3950235) CF 3 CF 3 CF 3 CF 2 CF_, - C - C - CF 3 (III) CF 3 F (Chemical Abstract Vol. 101, 12.153U) CF, CF, CF. - C - C C - F (IV) CF 3 CF 2 CF 2 F CF. CF 3 CF 3 This product is prepared according to US-A-3950235 ♦ Other branched perfluoroalkanes belonging to this class are the new compounds having the following formulas: CF 3 CF 3 CF 3 CF 3 CF 3 CF 3 1 1 1 I I I CF - C - CF CF - C - CF CF 3 CF 3 CF 3 CF 3 CF 2 CF 3 CF 3 (V) (VI) In particular compounds (V) and (VI) , having adjacent two tertiary and quaternary carbon atoms, although stable at room temperature, decompose at temperatures > 70°C preferably at temperatures * 100°C, thereby generating radicals. For instance compounds (V) and (VI) , if heated at temperatures ranging from 100 to 160°C, decom¬ pose probably ' undergoing a homolytic scission of the C-C bound between the tertiary and quaternary carbon atoms according to the following scheme: 2 and after some time the following products are obtained, in the same ratio (VII) (VIII) (IX) The perfluoroal anes, having the above mentioned characteristics, are suitable for being used as polymeri¬ zation initiators of halogenated or partly halogenated defines, or mixtures thereof and of other ethylenically unsaturated monomers, and in particular of fluorinated monomers . A further object of the present invention consists in the new branched perfluoroal anes of formula (V) and (VI) and in their preparation by subjecting the per- fluorinated olefin having the following formula: alone or in the presence of a perfluoropropene having the formul a which are trimers of hexafluoropropene obtained according to US-A-3917724 to a fl-uori nation treatment with elemental fluorine in the presence of UV radiation at temperatures of from -15 to 50°C, preferably of from -10 to +10°C. The reaction can be carried out either in the presence of an inert gas or with fluorine alone. The fluorination reaction according to the present invention can be suitably carried out in the liquid phase in the presence of a perfluori nated inert solvent prefera¬ bly a perfluoropolyether having a molecular weight com¬ prised within the range of from 800 to 2000 selected form the following classes: a) CF_o0(C 9 F4.0)p (CF-0)q - CF_ i wherein p and q are integers and the p/q ratio ranges from 1 to 0.5. The units C„F.0 and CF.O are randomly 2 4 2 J distributed along the chain; b) Rf0(C,F c 0) (CFX0) Rf 3 6 m n wherein Rf is CF ,C F or 3 F_, ; X is either F or CF 3 , m and n are integers chosen so as to fulfil the condition that the molecular weight be in the range from 800 to 2000; c) C 3 F 7 0(C 3 F 6 0) χ C 2 F 5 wherein x is an integer chosen so as to fulfil the conditio that the molecular weight be in the range from 800 to 2000; d) R'f(CF.CF_0) R'f n wherein n is an integer chosen so as to fulfil the above- - 8 - mentioned condition and R'f is CF, or C„F C ; ό c e) A(CF_CF.CF_0) B 2 2 2 n wherein n is an integer chosen so as to fulfil the above condition , A is F or ORf, and B is Rf or C 3_F_/;' f) perf1 uoropolyethers containiπ-g- repeating units (C F 0), (C-F-0), (CFXO) and having a molecular weight of 3 o from 800 to 2000; _ » " CF Rf Rf wherein R f is a perfluoroalkyl group or F, n is an integer chosen Kt so as to fulfil the above condition and Rf is a perfluoroalkyl gro The new branched perfluoroal anes of formula (V) and (VI) are obtained according to the present invention in the presence of a new thermally stable perfluorooctane, per- fluoro-2, 3 ,4-trimethylpentane, which is described in IT-A- 20060/87.- This perfluorooctane can be easily removed from the perfluoroalkanes according to the present invention by rectification, since it has a lower boiling point than the branched perfluoroalkanes of the present invention. The perfluoroal anes of formula (V) and (VI) are obtained with a high purity degree. Example 1 362.2 g (0.81 moles) of tri er having formula (VII) were loaded into a 250 ml quartz reactor , having an optical path of 6.45 mm; after keeping the apparatus under N the compound was irradiated by means of a Hg high pressure lamp (Hainnaa®utr TT(Q 150, whose wavelength ranged from 250 to 400 nanometers) , by maintaining a fluorine flow of 1 1/h, diluted with an equal flow of N . The reactor temperature was kept at 28°C over 30 hours, the reaction course was followed by gaschromatographi c analysis. At the end 358 g of raw product were unloaded and 18 g of low boiling products were collected in the traps, cooled at -80°C, placed under the reactor. The two raw products, after being collected, were subjected to rectification, thereby obtaining a first fraction consisting- of perfluoroalkanes having a carbon atom number lower than or equal to 8, afterwards the following compounds (XII), (V) (VI) were isolated, in a mol ar rati o : 1 : 10 : 1. . CF. CF„-CF. (XII) (V) (VI) Compound (XII) is a known product (S.P. , Von Halasz F. Kenye and T. Martini, Chem. Ber.,Vol . 106 2950-2959 (1973) . Products (V) and (VI) were isolated in a total amount of 160 g . The product having formula (V) had a boiling point of 140°C, whereas the product having formula (VI) had a boiling point of 153°C at 760 mm Hg. The structure of products (VI and (VI) was 19 determined by gaschromatography, IR and NMR- analysis . 19, The Chemical Shifts relating to NMR IS F analysis ( O. CFC1,) of product (V) we ' re the following: (b)CF 3 CF 3 (c) CF 3 (b) (a)CF CF (a) ( b ) CF 3 CF 3 (c) CF 3 (b) ( a ) : 161 ppm ( b ) : 66 ppm ( c ) : 55 ppm 19 The Chemical Shifts relating to NMR F - analysis of product (VI) were the following: (b)CF. (c)CF. CF 3 (b) (a)CF CF (a) CF 3 (b) (b)CF. CF 2 CF 3 (d) (e) (a) : 161 ppm (b) : 66 ppm (c) : 54 ppm (d) : 92 ppm (e) : 75 ppm By heating perf1 uoroalkane (V) at 160°C over 20 hours in sealed glass phials, one noted its complete decomposi¬ tion and formation of products (VII), (VIII) (IX) in an equal molar ratio among themselves. Perf1 uoroal kane (VI) underwent similar scission as well , if it was subjected to heating. Example 2 Into a 200 ml quartz reactor having an optical path of 6.45 mm, 81 g (0.18 moles) of a mixture containing 94% by weight of the trimer of formula (X) and 6% by weight or of the (R) trimer of formula (XI) and 197 g of FOMBLIN^ Y, that is a perf1 uoropo lyether belonging to class (b) and having a molecular weight 1800 were loaded. After keeping the reactor under inert atmosphere the reaction solution having a temperature of 28°C was irradiated by means of the Hg high pressure lamp of example 1 contemporaneously maintaining a fluorine flow of 1 1/h. After 14 hours the solution is discharged and separated from the solvent by distillation. After rectification 76 g of products are collected which according to gaschromatographic analysis contained 50% of product of formula (V) and 4% of product of formula (VI) and 15% of perf1 uorooctane as disclosed in IT-A-20060 A/87. This compound is subsequently separated by perf 1 uorononane and perf1 uorodecane of formula (V) and (VI) by rectifi¬ cation. Example 3 The reaction of example 2 was carried out at 15°C. After 14 hours the reaction solution was discharged and distilled in order to separate the reaction product from the solvent. 77 g of raw products were obtained, which according to gaschromatographic analysis contained 52% of compound having formula (V) and 28% of the perfluoro- octane and 3% of perf1 uorodecane having formula (VI). The perf1 uorooctane is subsequently separated from the other products by rectif cation. Example 4 The reaction of example 2 was carried out at 5°C. After 14 hours the reaction solution was discharged and distilled in order to separate the reaction product from the solvent. 80 g of raw products were obtained, which according to gaschromatographic analysis contained 43% of perfluorononane of formula (V) , 31% of perf1 uorooctane and 2% of perf1 uorodecane of formula (VI). The perf1 uorooctane is subsequently removed from the other compounds by rectification. Example 5 Following the procedure of example 1 the perfluoroal kane of formula (V) was decomposed at different temperatures and at different times. The decomposition was followed by gaschomatographic analysis the results of which are shovm in the table below. TABLE I Time Temperature of product decomposed (h) (°C) 24 no 0.5 24 120 2.5 16 130 3.7 5 140 6 16 140 17.7 5 150 9.3 10 150 21.8 16 150 42.7 5 160 10.7 10 160 86.6 16 160 91.5 Example 6 Following the procedure of example 1, the perf1 uoroal kane of formula (I) was decomposed at different times and temperatures. The results are reported in the following table. TABLE II | Time Temperature % of product decomposed 1 (h) (°C) 1 5 160 1 | 1 10 160 1.5 | 1 16 160 2.5 | 1 8 180 12.5 | 1 16 180 24 | E x amp l e 7 0.05 g of perf1 uoroal ane (V) were loaded into a glass reactor having a volume of 30 ml and an inner diameter of 1 cm and, after degassing r 2 g of C~F. were condensed; heated at 140°C and a few minutes later the formation was observed of a white polymeric product, insoluble in conventional organic solvents and whose IR analysis and differential thermal analysis were concordant with the typical structure of a homopolymer of C F.. Example 8 0.05 g of a mixture of perfluoroalkanes ( v) and (VI) in a molar ratio 10:1 , 2 g of C F. and 6 g of C,F C were 4 o reacted in a reactor similar to the one of the preceding example. After heating at 160°C over 1 hour and 20 minutes the formation of a white polymeric solid was observed, with a structure ( IR analysis) showing the presence of chains (C^F ) and the presence of units -CF CF-. I Noted was the formation of a co-polymer C2 F 4 /C,F,-. Example 9 By using the same reactor as in example 2, 0.05 g of initiator (V) and 3 g of styrene were reacted at 120°C « over 8 hours. At the end of this period of time the presence of a polymeric solid , whose analysis was concordant with the polystyrene structure, was noted in the reactor. Example 10 Into the same reactor as in example 7, 1.4 g of TFE (0.014 moles) and 39.04 g of perf1uoroal ane of formula (V) were introduced. The mixture was heated to 104°C. After 1 hour and 20 minutes the mixture was discharged and dried; 905 mg of a product having a molecular weight of 1.095 x 10 were obtained.

Claims: CLAIMS 1) A process for the polymerization of ethylenically un¬ saturated monomers comprising ^ as polymerization ini¬ tiator, a branched perfluoroalkane or a mixture of branched perfluoroalkanes having adjacent two quaternary carbon atoms or a quaternary carbon atom and a tertiary carbon atom, said per luoroalkane having at least 9 carbon atoms. 2) The process according to claim 1 in which as polymeriza¬ tion initiator the perf1 uoroal kane of formula (I) is used ; CF C - CF. (I) CF 3 CF 2 - CF 3 3) The process according to claim 1 in which as polymeriza¬ tion initiators the perfluoroa.lkanes having the following formulas or a mixture thereof are used: CF 3 CF 2 -CF 3 F-C C ■ CF. (II) CF 2 CF 2 - CF 3 CF 3 CF, CF. CF 3 CF 2 CF 2 - C - C - CF. (Ill) CF, F CF, CF, CF. CF, CF. (iv; CF, CF, CF. CF. 4) Branched perfluoroal anes having the following formulas CF 3 CF 3 CF 3 CF 3 CF 3 CF 3 CF - C - CF CF - C - CF CF 3 CF 3 CF 3 CF 3 CF 2 CF 3 CF 3 (V) ( vi ) 5) The process according to claim 1 in which the polymeriza¬ tion initiators used are the perfluoroal anes of claim 4, the polymerization reaction being carried out at temperatures > 70°C , preferably at temperatures 100°C. 6) A process for preparing he compounds of formulas V and VI according to claim 4, which comprises reacting the olefin of formula: alone or in the presence of a perfluoropropene having the formula with elemental fluorine in the presence of U V radiation at temperatures of from -15°C to +50°C, prefer¬ ably of from -10°C to +10°C. 7) The process according to claim 6 in which the fluorina- tion reaction is carried out in the presence of a per- fluorinated inert solvent. 8) The process according to claim 7 in which the perfluori- nated solvent is a perf1uoropolyether having a molecular weight comprised within the range of from 800 to 2000 selected from the following classes: a) CF.0(C,F.0) (CF_0) - CF, 3 Z 4 p 2 q 3 wherein p and q are integers and the p/q ratio ranges from 1 to 0.5, the units C F 0 and CF 0 being randomly distributed along the chain; b) RfO(C.F.O) (CFXO) Rf 3 b m n wherein Rf is CF, ,C,F C or C-F_ , X is either F or CF, m 6 ) 6 I S and n are integers chosen so as to fulfil the condition that the molecular weight be in the range.from 800 to 2000; c) C,F 7 0(C-F.0) C,F, 3 7 3 6 x 2 5 wherein x is an i nteger chosen so as to fulfil the condition that the molecular weight be comprised in the above defined range; d) R'f(CF.CF-O) R'f c a wherein n i s an i nteger chosen so as to fulfil the condition that the molecular weight be comprised in the above defined range and R'fis CF_ or C,F C ; 3 e) A(CF,CF_CF 0) B Z Z Z n wherein n i s an integer chosen so as to fulfil the abov condition, " A is F or OR'f, and B is R'f or C 3 F ? f) perfluoropolyethers containing repeating units (C,F 0), (CF 0) (CFXO) and having a molecular weight comprised in the above range; CF 3 Rf Rf wherein R"f is a perfluoroalkyl group or F, n is an integer chosen so as to fulfil the above condition, and R'"f is a perfluoroalkyl group.

Inventors: TONELLI CLAUDIO, TORTELLI VITO, TONELLI, CLAUDIO, TORTELLI, VITO
Applicants: AUSIMONT SPA, AUSIMONT S.P.A.
Application year: 1988
Main classification: C08F4
IPC codes: C07C17, C07C19, C08F2, C08F4, C08F214