5
Ind. Eng. Chem. Prod. Res. Dev. 1983, 22, 5-8
suggests that modification of the structure of the sodium silicate into a material that is more like silica gel is an important part of the cure. Registry No. Cu20, 1317-39-1;ZnO, 1314-13-2;Ti02,1346367-7; sodium silicate, 1344-09-8.
Literature Cited
Kuzln, V. A.; Orlov, V. A.; Kilmenko. N. S. Lakokras. Meter. Ikh Primen. 1077, 6 , 31.
Pass, A.; Meason, M. J. F. J . OIICo. Chem. Assoc. 1085, 48, 097. Rlschbieth, J. R.; Marson, F. Nature (London) 1981, 748. Rlschbieth, J. R.; Marson, F. J . Oil Co. Chem. Assoc. 1983, 4 6 , 499. Stumm, W.; HUper, H.; Champlln, R. I . Environ. Sci. Techno/. 1087, 1 , 21 1. Wright, M. 0. B.; Madge, J. W.; Bond, M.; Crowl, V. T. “Surface Characterlstlcs of Metallic Zinc Pigments”; International Lead Zinc Research Organisation: New York, Project ZC 162, 1970.
Dent Glesser, L. S.; Gard,J. A.; Lachowski, E. E. J . Appl. Chem. Blotechnol.
Received for review March 9, 1982 Accepted August 27, 1982
1078, 28. 799. Harrls, R. K.; Knight, C. T.; Hull, W. E. J . Am. Chem. SOC.1081, 703, 1577.
I I.
Symposium on Fluoropolymers K. J. L. Paciorek, Chairman 183rd National Meeting of the American Chemical Society Las Vegas, Nevada, March 1982
Copolymerization Studies of Fluorinated Epoxides Kazlmlera J. L. Paclorek,’ Thomas I. Ito, James H. Nakahara, and Relnhold H. Kratrer Uttrasystems, Inc., 2400 Michelson Drive, Imine, California 927 15
Telomerizations of perfluoro-1,Bepoxyheptane and 4-chloro- and 4-bromoheptafluoro-l,2-epoxybutanes with hexafluoropropene oxide at 0 and -23 OC afforded as major products room temperature involatile copolymers of 3000 average molecular weight. At higher temperatures, substantial quantities of low molecular weight telomers were obtained. The nature of the products formed with respect to the arrangement of the epoxide units was determined by mass spectrometry. The investigations showed that true copolymers were formed.
-
Introduction Pertluoroalkylethers belong to a class of low Tgthermally and oxidatively stable materials and as such present potential candidates for fluid and elastomer applications where extremes of temperatures are to be encountered. To date, these compositions were found to provide fluids and lubricants (Binaghi et al., 1973; Gumprecht, 1966, 1967; Lawson, 1970; Sianesi et al., 1971; Snyder and Dolle, 1976). A practical elastomer must possess a sufficiently high molecular weight and be amenable to cross-linking. The chemical inertness of the perfluoroalkyl ether chain precludes cross-linking without an introduction of functional sites. The current investigation was undertaken to determine the feasibility of copolymerizing hexafluoropropene oxide with oxides containing side chains other than trifluoromethyl with the ultimate objective to incorporate a bromine-terminated pendant group into the polymer chain. Results and Discussion In the telomerization reactions, hexafluoropropeneoxide and was copolymerized with perfluoro-l,2-epoxy-n-heptane 4-chloro- and 4-bromoheptafluoro-1,2-epoxybutanes.The experimental procedures were based essentially on the work of Anderson (19681, but in the current studies, higher temperatures were utilized. To optimize the polymerization conditions, homopolymerizations of hexafluoropropene oxide were also carried out. These experiments are summarized in Table I. It should be noted that of the four epoxides, hexafluoropropene oxide is most volatile, bp -28 “C (Sianesi et al., 1966), whereas the perfluoro0 196-4321 16311222-0005$01.50/0
heptene oxide (VPoec,18 mm) is the least volatile. The 4-chloroepoxybutane (VPooc,199 mm) (Ito et al., 1979) is significantly more volatile than its bromo analogue ( VPaoc, 99 mm) (Ito et al., 1979). The copolymerization of hexafluoropropene oxide with perfluoroheptene oxide resulted in the incorporation of approximately 50% of the available heptene oxide. Yet, the consumption of hexafluoropropene oxide was higher than that observed on its homopolymerization where up to 10% unreacted epoxide was recovered. This would indicate that, although perfluoroheptene oxide appears to be less reactive than hexafluoropropene oxide, it performs a solvent function for the telomerization process. The ratio of C7FI40to C3F60units in the resultant polymer was calculated to be 1:7.8 based on the recovered perfluoroheptene oxide. This value is in good agreement with the ratio of 1:7.5 obtained by NMR analysis; the NMR data also confirmed that a true copolymer was formed. The major portion of the research effort was centered on the copolymerizationsof hexafluoropropeneoxide with 4-chloroheptafluoro-l,2-epoxybutane.The chloro moiety is not sufficiently reactive to provide a functional cross-link site; however, there is a close similarity between 4chloroheptafluoro-1,Zepoxybutaneand its bromo analogue to utilize the former to evaluate and optimize the reaction conditions. This approach was prompted by the relative availability of the precursor 1,1,1,5-tetrachloroperfluoropentane as compared to l,l,l-trichloro-5-bromoperfluoropentane (Ito et al., 1979). Examining the data in Table I, it is evident that the lower the temperature of polymerization and the lower the relative amount of cesium 0 1983 American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 1, 1983
6
Table I. Summary of Telomerization Reactions reagents test no.
1 24 2 4
C,F,O, mmol
(R)CFCF,O, mmol
30.6 ( 5 ) d 14.8 (10) 14.1 ( 4 0 ) 24.6 (1)
products
conditions
R = CF,(CF,), 6.3 ( 5 6 )
time
polymer
h
CsF, mol %
%
MW
-23 -23 -23
16 16 8
0.3 0.3 0.3
91 89 57
3600 3500 2600
3.1 1.2 2.5
-23
16
0.3
79
2800
trace
-23
24 40
20 17 15 15 4 2
2 .o 2.0 6.5 6.5 4.2 6.5
99 99 97 95 73 67
2200 1700 1300 1300 1200 800
1.3 1.3 3.3 5.2 11.2 32.2
-23 -23
16 51
2 .o 1.8
87 91
1900 1600
-8
T, "C
telb
%C
R = Cl(CF,), 8 7 10 11 9 12
4.2 4.2 6.0 3.0 2.0 ( 1 6 ) 1.5 (1.5)
21 27
2.1 4 . 8 (1)
2.1 2.1 3.0 3.0 1.0 ( 1 5 ) 1 . 5 (1)
R
a
=
0
0 0
Br(CF,),
1.0 (27) 2.4 ( 2 )
-4
Material involatile in vacuo at 25 "C. Low molecular weight telomers volatile at 25 "C in vacuo. Percent of total The values given in the parentheses correspond to the percent of the oxide recovered.
oxide or oxides used.
fluoride catalyst, the higher the yield and the molecular weight of the room temperature involatile telomers, which is to be expected for an ionic polymerization. Most of the telomerizations were carried out utilizing a 2:l ratio of hexafluoropropene oxide to the chloroepoxide. The change in the ratio to 1:l did not seem to affect the yield or molecular weight of the polymer. The high recovery of the starting materials in the room temperature telomerization is most likely caused by the short reaction period. It should be noted that the -23 and 0 OC reactions were carried out with the bulk of the reagents in the condensed phase; in the 24 and 40 "C tests the major portion of the reagents was in the gas phase. One would expect the cotelomerizations of the 4bromoheptafluoro-1,2-epoxybutanewith hexafluoropropene oxide to proceed in a manner parallel to that encountered with the chloro analogue. Comparison of test no. 8 and 21 reveals that, although the molecular weights of the involatile polymers are not widely different, the recovery of starting material is substantial in test no. 21. Longer reaction times were required (test no. 27) to achieve better conversions. This was, however, accompanied by a further drop in molecular weight. Actually, great difficulties were encountered to have the reaction proceed. In a number of unsuccessful trials, no telomerization took place and thus these tests are not listed in Table I. It was subsequently found that the presence of small quantities (
